diff --git a/fixtures/m11-pong-key.json b/fixtures/m11-pong-key.json
new file mode 100644
index 0000000..df9e7e2
--- /dev/null
+++ b/fixtures/m11-pong-key.json
@@ -0,0 +1,151 @@
+{
+  "function": "pongKey",
+  "cases": [
+    {
+      "name": "ArrowUp-down-presses-up",
+      "args": [
+        true,
+        "ArrowUp"
+      ],
+      "expected": {
+        "tag": "Press",
+        "key": "Up"
+      }
+    },
+    {
+      "name": "ArrowUp-up-releases-up",
+      "args": [
+        false,
+        "ArrowUp"
+      ],
+      "expected": {
+        "tag": "Release",
+        "key": "Up"
+      }
+    },
+    {
+      "name": "w-down-presses-up",
+      "args": [
+        true,
+        "w"
+      ],
+      "expected": {
+        "tag": "Press",
+        "key": "Up"
+      }
+    },
+    {
+      "name": "w-up-releases-up",
+      "args": [
+        false,
+        "w"
+      ],
+      "expected": {
+        "tag": "Release",
+        "key": "Up"
+      }
+    },
+    {
+      "name": "ArrowDown-down-presses-down",
+      "args": [
+        true,
+        "ArrowDown"
+      ],
+      "expected": {
+        "tag": "Press",
+        "key": "Down"
+      }
+    },
+    {
+      "name": "ArrowDown-up-releases-down",
+      "args": [
+        false,
+        "ArrowDown"
+      ],
+      "expected": {
+        "tag": "Release",
+        "key": "Down"
+      }
+    },
+    {
+      "name": "s-down-presses-down",
+      "args": [
+        true,
+        "s"
+      ],
+      "expected": {
+        "tag": "Press",
+        "key": "Down"
+      }
+    },
+    {
+      "name": "s-up-releases-down",
+      "args": [
+        false,
+        "s"
+      ],
+      "expected": {
+        "tag": "Release",
+        "key": "Down"
+      }
+    },
+    {
+      "name": "r-down-restarts",
+      "args": [
+        true,
+        "r"
+      ],
+      "expected": {
+        "tag": "Restart"
+      }
+    },
+    {
+      "name": "r-up-does-nothing",
+      "args": [
+        false,
+        "r"
+      ],
+      "expected": null
+    },
+    {
+      "name": "other-key-down-is-ignored",
+      "args": [
+        true,
+        "x"
+      ],
+      "expected": null
+    },
+    {
+      "name": "other-key-up-is-ignored",
+      "args": [
+        false,
+        "x"
+      ],
+      "expected": null
+    },
+    {
+      "name": "space-is-ignored",
+      "args": [
+        true,
+        " "
+      ],
+      "expected": null
+    },
+    {
+      "name": "constructor-is-not-a-key",
+      "args": [
+        true,
+        "constructor"
+      ],
+      "expected": null
+    },
+    {
+      "name": "toString-is-not-a-key",
+      "args": [
+        false,
+        "toString"
+      ],
+      "expected": null
+    }
+  ]
+}
diff --git a/fixtures/m11-pong-update.json b/fixtures/m11-pong-update.json
new file mode 100644
index 0000000..89bb71c
--- /dev/null
+++ b/fixtures/m11-pong-update.json
@@ -0,0 +1,2226 @@
+{
+  "function": "pongUpdate",
+  "cases": [
+    {
+      "name": "press-up-holds-up",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Press",
+          "key": "Up"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "press-down-holds-down",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Press",
+          "key": "Down"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "press-keeps-the-other-key-held",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Press",
+          "key": "Down"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "release-up",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": true
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Release",
+          "key": "Up"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "release-down",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": true
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Release",
+          "key": "Down"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "release-of-a-key-not-held-changes-nothing",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Release",
+          "key": "Up"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "press-is-recorded-even-when-the-match-is-over",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Over",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Press",
+          "key": "Up"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Over",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "frame-moves-the-ball-and-counts-the-frame",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "frame-up-key-moves-the-player-up",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 20,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "frame-down-key-moves-the-player-down",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": true
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 22,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "frame-both-keys-cancel-out",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": true
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "player-stops-at-the-top-edge",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 0,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 0,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "player-stops-at-the-bottom-edge-42",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 42,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": true
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 26
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 42,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": true
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "cpu-does-not-move-on-an-odd-frame",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 40
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 41
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 1
+      }
+    },
+    {
+      "name": "cpu-moves-down-toward-the-ball-on-an-even-frame",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 40
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 1
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 41
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 22,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 2
+      }
+    },
+    {
+      "name": "cpu-moves-down-again-on-frame-four",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 40
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 3
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 41,
+          "y": 41
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 22,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 0,
+        "frame": 4
+      }
+    },
+    {
+      "name": "cpu-moves-up-toward-the-ball",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 5
+          },
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+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": -1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 2,
+          "cpu": 4
+        },
+        "status": "Playing",
+        "seed": 1831565813,
+        "frame": 1
+      }
+    },
+    {
+      "name": "player-reaching-five-ends-the-match",
+      "args": [
+        {
+          "ball": {
+            "x": 79,
+            "y": 10
+          },
+          "vel": {
+            "dx": 1,
+            "dy": -1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 4,
+            "cpu": 2
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 5,
+          "cpu": 2
+        },
+        "status": "Over",
+        "seed": 1831565813,
+        "frame": 1
+      }
+    },
+    {
+      "name": "cpu-reaching-five-ends-the-match",
+      "args": [
+        {
+          "ball": {
+            "x": 0,
+            "y": 25
+          },
+          "vel": {
+            "dx": -1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 1,
+            "cpu": 4
+          },
+          "status": "Playing",
+          "seed": 1,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": -1,
+          "dy": -1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 1,
+          "cpu": 5
+        },
+        "status": "Over",
+        "seed": 1831565814,
+        "frame": 1
+      }
+    },
+    {
+      "name": "frame-when-over-changes-nothing",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": true,
+            "down": false
+          },
+          "score": {
+            "player": 5,
+            "cpu": 1
+          },
+          "status": "Over",
+          "seed": 0,
+          "frame": 0
+        },
+        {
+          "tag": "Frame"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": true,
+          "down": false
+        },
+        "score": {
+          "player": 5,
+          "cpu": 1
+        },
+        "status": "Over",
+        "seed": 0,
+        "frame": 0
+      }
+    },
+    {
+      "name": "restart-starts-a-new-match-with-the-same-seed",
+      "args": [
+        {
+          "ball": {
+            "x": 12,
+            "y": 9
+          },
+          "vel": {
+            "dx": -1,
+            "dy": -1
+          },
+          "player": 5,
+          "cpu": 30,
+          "held": {
+            "up": true,
+            "down": true
+          },
+          "score": {
+            "player": 3,
+            "cpu": 2
+          },
+          "status": "Playing",
+          "seed": 7,
+          "frame": 99
+        },
+        {
+          "tag": "Restart"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 7,
+        "frame": 0
+      }
+    },
+    {
+      "name": "restart-after-the-match-is-over",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 5,
+            "cpu": 3
+          },
+          "status": "Over",
+          "seed": 1831565813,
+          "frame": 321
+        },
+        {
+          "tag": "Restart"
+        }
+      ],
+      "expected": {
+        "ball": {
+          "x": 40,
+          "y": 25
+        },
+        "vel": {
+          "dx": 1,
+          "dy": 1
+        },
+        "player": 21,
+        "cpu": 21,
+        "held": {
+          "up": false,
+          "down": false
+        },
+        "score": {
+          "player": 0,
+          "cpu": 0
+        },
+        "status": "Playing",
+        "seed": 1831565813,
+        "frame": 0
+      }
+    }
+  ]
+}
diff --git a/fixtures/m11-pong-view.json b/fixtures/m11-pong-view.json
new file mode 100644
index 0000000..d2e0f1c
--- /dev/null
+++ b/fixtures/m11-pong-view.json
@@ -0,0 +1,325 @@
+{
+  "function": "pongView",
+  "cases": [
+    {
+      "name": "new-match",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 0,
+            "cpu": 0
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        }
+      ],
+      "expected": [
+        {
+          "tag": "Rect",
+          "x": 0,
+          "y": 0,
+          "w": 640,
+          "h": 400,
+          "color": "#111111"
+        },
+        {
+          "tag": "Rect",
+          "x": 16,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 616,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 320,
+          "y": 200,
+          "w": 8,
+          "h": 8,
+          "color": "#ffeb3b"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 30,
+          "text": "0   0",
+          "color": "#ffffff",
+          "size": 24,
+          "align": "center"
+        }
+      ]
+    },
+    {
+      "name": "paddles-and-ball-move-with-the-state",
+      "args": [
+        {
+          "ball": {
+            "x": 10,
+            "y": 5
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 0,
+          "cpu": 42,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 3,
+            "cpu": 2
+          },
+          "status": "Playing",
+          "seed": 0,
+          "frame": 0
+        }
+      ],
+      "expected": [
+        {
+          "tag": "Rect",
+          "x": 0,
+          "y": 0,
+          "w": 640,
+          "h": 400,
+          "color": "#111111"
+        },
+        {
+          "tag": "Rect",
+          "x": 16,
+          "y": 0,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 616,
+          "y": 336,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 80,
+          "y": 40,
+          "w": 8,
+          "h": 8,
+          "color": "#ffeb3b"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 30,
+          "text": "3   2",
+          "color": "#ffffff",
+          "size": 24,
+          "align": "center"
+        }
+      ]
+    },
+    {
+      "name": "player-wins",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 5,
+            "cpu": 3
+          },
+          "status": "Over",
+          "seed": 0,
+          "frame": 0
+        }
+      ],
+      "expected": [
+        {
+          "tag": "Rect",
+          "x": 0,
+          "y": 0,
+          "w": 640,
+          "h": 400,
+          "color": "#111111"
+        },
+        {
+          "tag": "Rect",
+          "x": 16,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 616,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 320,
+          "y": 200,
+          "w": 8,
+          "h": 8,
+          "color": "#ffeb3b"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 30,
+          "text": "5   3",
+          "color": "#ffffff",
+          "size": 24,
+          "align": "center"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 200,
+          "text": "You Win!",
+          "color": "#ffffff",
+          "size": 32,
+          "align": "center"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 230,
+          "text": "Press R to restart",
+          "color": "#ffffff",
+          "size": 16,
+          "align": "center"
+        }
+      ]
+    },
+    {
+      "name": "cpu-wins",
+      "args": [
+        {
+          "ball": {
+            "x": 40,
+            "y": 25
+          },
+          "vel": {
+            "dx": 1,
+            "dy": 1
+          },
+          "player": 21,
+          "cpu": 21,
+          "held": {
+            "up": false,
+            "down": false
+          },
+          "score": {
+            "player": 2,
+            "cpu": 5
+          },
+          "status": "Over",
+          "seed": 0,
+          "frame": 0
+        }
+      ],
+      "expected": [
+        {
+          "tag": "Rect",
+          "x": 0,
+          "y": 0,
+          "w": 640,
+          "h": 400,
+          "color": "#111111"
+        },
+        {
+          "tag": "Rect",
+          "x": 16,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 616,
+          "y": 168,
+          "w": 8,
+          "h": 64,
+          "color": "#ffffff"
+        },
+        {
+          "tag": "Rect",
+          "x": 320,
+          "y": 200,
+          "w": 8,
+          "h": 8,
+          "color": "#ffeb3b"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 30,
+          "text": "2   5",
+          "color": "#ffffff",
+          "size": 24,
+          "align": "center"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 200,
+          "text": "CPU Wins",
+          "color": "#ffffff",
+          "size": 32,
+          "align": "center"
+        },
+        {
+          "tag": "Text",
+          "x": 320,
+          "y": 230,
+          "text": "Press R to restart",
+          "color": "#ffffff",
+          "size": 16,
+          "align": "center"
+        }
+      ]
+    }
+  ]
+}
diff --git a/js/pong.html b/js/pong.html
new file mode 100644
index 0000000..253a345
--- /dev/null
+++ b/js/pong.html
@@ -0,0 +1,22 @@
+<!doctype html>
+<html lang="en">
+<head>
+  <meta charset="utf-8">
+  <meta name="viewport" content="width=device-width, initial-scale=1">
+  <title>Pure Pong</title>
+  <link rel="icon" href="data:,">
+  <style>
+    body { margin: 0; min-height: 100vh; display: flex; flex-direction: column; align-items: center;
+           justify-content: center; gap: 12px; background: #1b1b1b; color: #ddd; font: 14px system-ui, sans-serif; }
+    h1 { margin: 0; font-size: 20px; }
+    canvas { background: #111111; border: 2px solid #333; }
+    p { margin: 0; color: #999; }
+  </style>
+</head>
+<body>
+  <h1>Pure Pong</h1>
+  <canvas id="game" width="640" height="400"></canvas>
+  <p>Up/Down arrows (or W/S) move your paddle. First to 5 wins. R restarts.</p>
+  <script type="module" src="src/pong/main.js"></script>
+</body>
+</html>
diff --git a/js/solutions/pong/app.js b/js/solutions/pong/app.js
new file mode 100644
index 0000000..0415419
--- /dev/null
+++ b/js/solutions/pong/app.js
@@ -0,0 +1,31 @@
+// m11 pong app: the same wiring as app.js (streams in, drawings out), reusing the course's modules.
+import { initialPong, PongAction } from './model.js'
+import { pongUpdate } from './rules.js'
+import { pongView } from './view.js'
+import { map as mapIO, randomSeed, drawScene } from '../io.js'
+import { keyDowns, keyUps, interval, map, filterMap, merge, scan, startWith } from '../stream.js'
+
+export const FRAME_MS_PONG = 30
+
+const keys = {
+  ArrowUp: 'Up', w: 'Up',
+  ArrowDown: 'Down', s: 'Down',
+}
+
+// hasOwn, not `key in keys`: "constructor" and "toString" are inherited, not keys we mapped.
+export const pongKey = (isDown, key) =>
+  Object.hasOwn(keys, key) ? (isDown ? PongAction.Press : PongAction.Release)(keys[key])
+    : key === 'r' && isDown ? PongAction.Restart
+    : null
+
+export const pongActions = merge(
+  map(interval(FRAME_MS_PONG), () => PongAction.Frame),
+  merge(
+    filterMap(keyDowns, (key) => pongKey(true, key)),
+    filterMap(keyUps, (key) => pongKey(false, key))))
+
+export const pongStates = (seed, actions) =>
+  startWith(scan(actions, pongUpdate, initialPong(seed)), initialPong(seed))
+
+export const pongMain = mapIO(randomSeed, (seed) =>
+  map(pongStates(seed, pongActions), (state) => drawScene(pongView(state))))
diff --git a/js/solutions/pong/main.js b/js/solutions/pong/main.js
new file mode 100644
index 0000000..bcd6f45
--- /dev/null
+++ b/js/solutions/pong/main.js
@@ -0,0 +1,5 @@
+import { runApp } from '../runtime.js'
+import { browserPlatform } from '../browser.js'
+import { pongMain } from './app.js'
+
+runApp(pongMain, browserPlatform(document.getElementById('game'), window))
diff --git a/js/solutions/pong/model.js b/js/solutions/pong/model.js
new file mode 100644
index 0000000..216bfe3
--- /dev/null
+++ b/js/solutions/pong/model.js
@@ -0,0 +1,38 @@
+// m11 pong model: the same ideas as the snake model, for a different game.
+
+/** @typedef {{ball: {x: number, y: number}, vel: {dx: number, dy: number}, player: number, cpu: number,
+ *   held: {up: boolean, down: boolean}, score: {player: number, cpu: number},
+ *   status: 'Playing'|'Over', seed: number, frame: number}} PongState */
+
+// The court, in cells. `player` and `cpu` are the y of the top cell of each paddle.
+export const W = 80
+export const H = 50
+/** Pixels per cell. */
+export const PCELL = 8
+/** Paddle height in cells. */
+export const PADDLE = 8
+/** Column of the player's paddle (left) and the cpu's paddle (right). */
+export const PLAYER_X = 2
+export const CPU_X = 77
+/** Points needed to win the match. */
+export const WIN = 5
+
+export const initialPong = (seed) => ({
+  ball: { x: 40, y: 25 },
+  vel: { dx: 1, dy: 1 },
+  player: 21,
+  cpu: 21,
+  held: { up: false, down: false },
+  score: { player: 0, cpu: 0 },
+  status: 'Playing',
+  seed,
+  frame: 0,
+})
+
+/** Everything that can happen in a match, as data. */
+export const PongAction = {
+  Press: (key) => ({ tag: 'Press', key }),
+  Release: (key) => ({ tag: 'Release', key }),
+  Frame: { tag: 'Frame' },
+  Restart: { tag: 'Restart' },
+}
diff --git a/js/solutions/pong/rules.js b/js/solutions/pong/rules.js
new file mode 100644
index 0000000..25d7117
--- /dev/null
+++ b/js/solutions/pong/rules.js
@@ -0,0 +1,67 @@
+// m11 pong rules: one pure `pongUpdate`, built from small steps that each return a new piece of state.
+import { H, W, PADDLE, PLAYER_X, CPU_X, WIN, initialPong } from './model.js'
+import { nextUint32 } from '../random.js'
+
+export const clamp = (lo, hi, x) => Math.min(hi, Math.max(lo, x))
+
+const clampPaddle = (y) => clamp(0, H - PADDLE, y)
+
+const movePlayer = (state) =>
+  clampPaddle(state.player + (state.held.down ? 1 : 0) - (state.held.up ? 1 : 0))
+
+// The cpu chases the middle of its paddle toward the ball, one cell every other frame.
+const moveCpu = (state, frame) =>
+  frame % 2 === 0 ? clampPaddle(state.cpu + Math.sign(state.ball.y - PADDLE / 2 - state.cpu)) : state.cpu
+
+const hits = (paddle, y) => paddle <= y && y < paddle + PADDLE
+
+// Where the ball goes next, given the paddles' new positions. `scorer` says who got the point, if anyone.
+const moveBall = (state, player, cpu) => {
+  const { ball, vel } = state
+  const wall = ball.y + vel.dy < 0 || ball.y + vel.dy >= H
+  const dy = wall ? -vel.dy : vel.dy
+  const ny = ball.y + dy
+  const nx = ball.x + vel.dx
+  const bounce =
+    (nx === PLAYER_X && vel.dx < 0 && hits(player, ny)) ||
+    (nx === CPU_X && vel.dx > 0 && hits(cpu, ny))
+  return {
+    ball: { x: bounce ? ball.x : nx, y: ny },
+    vel: { dx: bounce ? -vel.dx : vel.dx, dy },
+    scorer: nx < 0 ? 'cpu' : nx >= W ? 'player' : null,
+  }
+}
+
+// After a point the ball restarts in the middle, heading toward whoever conceded; the seed picks up or down.
+const serve = (state, scorer) => {
+  const [r, seed] = nextUint32(state.seed)
+  const score = { ...state.score, [scorer]: state.score[scorer] + 1 }
+  return {
+    ...state,
+    ball: { x: 40, y: 25 },
+    vel: { dx: scorer === 'cpu' ? -1 : 1, dy: r % 2 === 0 ? 1 : -1 },
+    score,
+    seed,
+    status: score[scorer] >= WIN ? 'Over' : 'Playing',
+  }
+}
+
+const frame = (state) => {
+  if (state.status !== 'Playing') return state
+  const n = state.frame + 1
+  const player = movePlayer(state)
+  const cpu = moveCpu(state, n)
+  const { scorer, ...moved } = moveBall(state, player, cpu)
+  const next = { ...state, ...moved, player, cpu, frame: n }
+  return scorer === null ? next : serve(next, scorer)
+}
+
+export const pongUpdate = (state, action) => {
+  switch (action.tag) {
+    case 'Press': return { ...state, held: { ...state.held, [action.key.toLowerCase()]: true } }
+    case 'Release': return { ...state, held: { ...state.held, [action.key.toLowerCase()]: false } }
+    case 'Restart': return initialPong(state.seed)
+    case 'Frame': return frame(state)
+    default: return state
+  }
+}
diff --git a/js/solutions/pong/view.js b/js/solutions/pong/view.js
new file mode 100644
index 0000000..9ff9fc9
--- /dev/null
+++ b/js/solutions/pong/view.js
@@ -0,0 +1,24 @@
+// m11 pong view: the same Scene shapes as the snake view, so the same drawScene and runtime draw it.
+import { PCELL, PADDLE, PLAYER_X, CPU_X } from './model.js'
+
+const rect = (x, y, w, h, color) => ({ tag: 'Rect', x, y, w, h, color })
+const text = (x, y, str, size) => ({ tag: 'Text', x, y, text: str, color: '#ffffff', size, align: 'center' })
+
+const paddle = (column, y) => rect(column * PCELL, y * PCELL, PCELL, PADDLE * PCELL, '#ffffff')
+
+const overlay = (state) =>
+  state.status === 'Over'
+    ? [
+      text(320, 200, state.score.player > state.score.cpu ? 'You Win!' : 'CPU Wins', 32),
+      text(320, 230, 'Press R to restart', 16),
+    ]
+    : []
+
+export const pongView = (state) => [
+  rect(0, 0, 640, 400, '#111111'),
+  paddle(PLAYER_X, state.player),
+  paddle(CPU_X, state.cpu),
+  rect(state.ball.x * PCELL, state.ball.y * PCELL, PCELL, PCELL, '#ffeb3b'),
+  text(320, 30, `${state.score.player}   ${state.score.cpu}`, 24),
+  ...overlay(state),
+]
diff --git a/js/src/pong/app.js b/js/src/pong/app.js
new file mode 100644
index 0000000..dd3e177
--- /dev/null
+++ b/js/src/pong/app.js
@@ -0,0 +1,24 @@
+import { todo } from '../todo.js'
+import { pure } from '../io.js'
+
+/** Milliseconds between frames of the match. */
+export const FRAME_MS_PONG = 30
+
+/**
+ * Translate a key event into a `PongAction`, or `null`. `isDown` is true for a key press, false for a release.
+ * `ArrowUp`/`w` -> `Press('Up')` / `Release('Up')`, `ArrowDown`/`s` -> `Press('Down')` / `Release('Down')`,
+ * `r` -> `Restart` (on press only; releasing `r` does nothing). Any other key -> `null`.
+ */
+export const pongKey = (isDown, key) => todo('m11')
+
+/**
+ * Everything that can happen in a match: `Frame` every FRAME_MS_PONG (from `interval`), merged with the
+ * `pongKey(true, key)` of every key press and the `pongKey(false, key)` of every key release.
+ */
+export const pongActions = { step: () => todo('m11') }
+
+/** Fold the actions into a stream of states: start from `initialPong(seed)`, `pongUpdate` for each action, emit the initial state first. */
+export const pongStates = (seed, actions) => todo('m11')
+
+/** The whole program as a value, like `main`: ask for a seed, turn the stream of states into a stream of drawings of `pongView`. */
+export const pongMain = pure({ step: () => todo('m11') })
diff --git a/js/src/pong/main.js b/js/src/pong/main.js
new file mode 100644
index 0000000..bcd6f45
--- /dev/null
+++ b/js/src/pong/main.js
@@ -0,0 +1,5 @@
+import { runApp } from '../runtime.js'
+import { browserPlatform } from '../browser.js'
+import { pongMain } from './app.js'
+
+runApp(pongMain, browserPlatform(document.getElementById('game'), window))
diff --git a/js/src/pong/model.js b/js/src/pong/model.js
new file mode 100644
index 0000000..339caef
--- /dev/null
+++ b/js/src/pong/model.js
@@ -0,0 +1,36 @@
+import { todo } from '../todo.js'
+
+/** @typedef {{ball: {x: number, y: number}, vel: {dx: number, dy: number}, player: number, cpu: number,
+ *   held: {up: boolean, down: boolean}, score: {player: number, cpu: number},
+ *   status: 'Playing'|'Over', seed: number, frame: number}} PongState */
+
+// The court, in cells. `player` and `cpu` are the y of the top cell of each paddle.
+export const W = 80
+export const H = 50
+/** Pixels per cell. */
+export const PCELL = 8
+/** Paddle height in cells. */
+export const PADDLE = 8
+/** Column of the player's paddle (left) and the cpu's paddle (right). */
+export const PLAYER_X = 2
+export const CPU_X = 77
+/** Points needed to win the match. */
+export const WIN = 5
+
+/**
+ * A fresh match: ball at (40,25) moving (dx 1, dy 1), both paddles at y 21, no keys held,
+ * score 0 to 0, status 'Playing', the given seed, frame 0.
+ */
+export const initialPong = (seed) => todo('m11')
+
+/**
+ * Everything that can happen in a match, as data:
+ * `Press(key)` / `Release(key)` for key 'Up' or 'Down' (`{tag, key}`), and `Frame` / `Restart` (`{tag}`).
+ * The getters only exist so the stub compiles; replace them with plain values.
+ */
+export const PongAction = {
+  Press: (key) => todo('m11'),
+  Release: (key) => todo('m11'),
+  get Frame() { return todo('m11') },
+  get Restart() { return todo('m11') },
+}
diff --git a/js/src/pong/rules.js b/js/src/pong/rules.js
new file mode 100644
index 0000000..65140b3
--- /dev/null
+++ b/js/src/pong/rules.js
@@ -0,0 +1,26 @@
+import { todo } from '../todo.js'
+
+/** Keep `x` inside `[lo, hi]`. */
+export const clamp = (lo, hi, x) => todo('m11')
+
+/**
+ * The one function that says how a match changes: `(state, action) -> state`.
+ *
+ * - `Press(key)` / `Release(key)`: set `held.up` or `held.down` (even when the match is over).
+ * - `Restart`: `initialPong(state.seed)`.
+ * - `Frame`: unchanged unless status is 'Playing'. Otherwise, in this order:
+ *   1. `frame + 1`.
+ *   2. The player moves one cell down for `held.down` and one up for `held.up` (both cancel out),
+ *      kept within `[0, H - PADDLE]`.
+ *   3. When the new `frame` is even, the cpu moves one cell toward `ball.y - PADDLE / 2` (it stays put when it is
+ *      already there), kept within `[0, H - PADDLE]`. It looks at the ball before the ball moves.
+ *   4. The ball moves vertically: `ny = y + dy`; if `ny < 0 || ny >= H` then `dy` flips and `ny = y + dy`.
+ *   5. Horizontally: `nx = x + dx`. It bounces (`dx` flips, `nx = x`) when `nx === PLAYER_X`, `dx < 0` and
+ *      `player <= ny < player + PADDLE` (using the player's new position), or when `nx === CPU_X`, `dx > 0` and
+ *      `cpu <= ny < cpu + PADDLE`.
+ *   6. If `nx < 0` the cpu scores; if `nx >= W` the player scores. A point serves a new ball: position (40,25),
+ *      `dx` toward the side that conceded (cpu scored -> -1, player scored -> +1), `dy = 1` when
+ *      `nextUint32(seed)` is even and `-1` otherwise, and the seed advances.
+ *   7. A score of `WIN` ends the match: status 'Over'.
+ */
+export const pongUpdate = (state, action) => todo('m11')
diff --git a/js/src/pong/view.js b/js/src/pong/view.js
new file mode 100644
index 0000000..08aee08
--- /dev/null
+++ b/js/src/pong/view.js
@@ -0,0 +1,11 @@
+import { todo } from '../todo.js'
+
+/**
+ * Describe the match as shapes, drawn in order (all text is '#ffffff', align 'center'):
+ * background Rect(0,0,640,400,'#111111'); player paddle Rect(PLAYER_X*8, player*8, 8, 64, '#ffffff'), then the
+ * cpu paddle the same way at CPU_X; ball Rect(x*8, y*8, 8, 8, '#ffeb3b');
+ * score Text(320, 30, '<player>   <cpu>' (three spaces), size 24).
+ * When Over: Text(320, 200, 'You Win!' if the player has more points, else 'CPU Wins', size 32) and
+ * Text(320, 230, 'Press R to restart', size 16).
+ */
+export const pongView = (state) => todo('m11')
diff --git a/js/test/m11-pong.test.js b/js/test/m11-pong.test.js
new file mode 100644
index 0000000..6f373e5
--- /dev/null
+++ b/js/test/m11-pong.test.js
@@ -0,0 +1,84 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { W, H, PCELL, PADDLE, PLAYER_X, CPU_X, WIN, initialPong, PongAction } from '../src/pong/model.js'
+import { pongUpdate, clamp } from '../src/pong/rules.js'
+import { pongView } from '../src/pong/view.js'
+import { pongKey, FRAME_MS_PONG, pongActions, pongStates, pongMain } from '../src/pong/app.js'
+import { run } from '../src/stream.js'
+import { trace } from '../src/io.js'
+import { loadFixture, freeze } from './helpers.js'
+
+const fixtureTests = (name, f) => {
+  const fx = loadFixture(name)
+  fx.cases.forEach((c) =>
+    test(`m11 ${fx.function}: ${c.name}`, () => assert.deepStrictEqual(f(...freeze(c.args)), c.expected)))
+}
+
+fixtureTests('m11-pong-update', pongUpdate)
+fixtureTests('m11-pong-view', pongView)
+fixtureTests('m11-pong-key', pongKey)
+
+const time = (t) => ({ tag: 'Time', t })
+const down = (key) => ({ tag: 'KeyDown', key })
+const up = (key) => ({ tag: 'KeyUp', key })
+
+test('m11 the court is 80 by 50 cells of 8 pixels, with 8-cell paddles', () =>
+  assert.deepStrictEqual([W, H, PCELL, PADDLE, PLAYER_X, CPU_X, WIN], [80, 50, 8, 8, 2, 77, 5]))
+
+test('m11 initialPong puts the ball in the middle, both paddles centred, and nobody ahead', () =>
+  assert.deepStrictEqual(initialPong(5), {
+    ball: { x: 40, y: 25 }, vel: { dx: 1, dy: 1 }, player: 21, cpu: 21,
+    held: { up: false, down: false }, score: { player: 0, cpu: 0 }, status: 'Playing', seed: 5, frame: 0,
+  }))
+
+test('m11 PongAction builds Press and Release with a key, and has Frame and Restart as plain values', () =>
+  assert.deepStrictEqual(
+    [PongAction.Press('Up'), PongAction.Release('Down'), PongAction.Frame, PongAction.Restart],
+    [{ tag: 'Press', key: 'Up' }, { tag: 'Release', key: 'Down' }, { tag: 'Frame' }, { tag: 'Restart' }]))
+
+test('m11 clamp keeps a number inside [lo, hi]', () =>
+  assert.deepStrictEqual([clamp(0, 42, -1), clamp(0, 42, 17), clamp(0, 42, 43)], [0, 17, 42]))
+
+test('m11 pongUpdate does not modify the state it is given', () => {
+  const s = freeze(initialPong(0))
+  assert.doesNotThrow(() => pongUpdate(s, PongAction.Frame))
+})
+
+// 3000 frames with no one touching the keys: the ball must always stay on the court and the match must end.
+test('m11 an idle match stays on the court and ends once someone reaches five', () => {
+  const states = Array.from({ length: 3000 }).reduce(
+    (acc) => [...acc, pongUpdate(acc[acc.length - 1], PongAction.Frame)], [initialPong(3)])
+  assert.ok(states.every((s) => s.ball.y >= 0 && s.ball.y < H && s.ball.x >= 0 && s.ball.x < W))
+  assert.ok(states.every((s) => s.player >= 0 && s.player <= H - PADDLE && s.cpu >= 0 && s.cpu <= H - PADDLE))
+  const last = states[states.length - 1]
+  assert.equal(last.status, 'Over')
+  assert.equal(Math.max(last.score.player, last.score.cpu), WIN)
+})
+
+test('m11 the clock runs every 30 ms', () => assert.equal(FRAME_MS_PONG, 30))
+
+test('m11 pongActions turns the clock into Frames and keys into Press, Release and Restart', () =>
+  assert.deepStrictEqual(
+    run(pongActions, freeze([time(30), down('ArrowUp'), up('ArrowUp'), down('s'), down('r'), up('r'), down('x'), time(90)])),
+    [PongAction.Frame, PongAction.Press('Up'), PongAction.Release('Up'), PongAction.Press('Down'), PongAction.Restart,
+      PongAction.Frame, PongAction.Frame]))
+
+test('m11 pongStates starts with the new match, then yields one state per action', () => {
+  const out = run(pongStates(42, pongActions), freeze([time(30), down('w'), time(60)]))
+  assert.equal(out.length, 4)
+  assert.deepStrictEqual(out[0], initialPong(42))
+  assert.deepStrictEqual(out.map((s) => s.frame), [0, 1, 1, 2])
+  assert.deepStrictEqual(out.map((s) => s.held.up), [false, false, true, true])
+  assert.deepStrictEqual(out[3].player, 20)
+})
+
+test('m11 pongMain asks for a seed, draws the new match first, and then the updated one', () => {
+  const { ops, result: stream } = trace(pongMain, 42)
+  assert.deepStrictEqual(ops, [{ tag: 'RandomSeed' }])
+  const [first, next] = stream.step(time(0))
+  const [second] = next.step(time(30))
+  assert.deepStrictEqual(trace(first[0], 0).ops.map((o) => o.shape), pongView(initialPong(42)))
+  assert.deepStrictEqual(
+    trace(second[0], 0).ops.map((o) => o.shape),
+    pongView(pongUpdate(initialPong(42), PongAction.Frame)))
+})
diff --git a/scripts/smoke.mjs b/scripts/smoke.mjs
index c0f82c3..2415b40 100644
--- a/scripts/smoke.mjs
+++ b/scripts/smoke.mjs
@@ -47,6 +47,7 @@ try {
   const ws = new WebSocket(target.webSocketDebuggerUrl)
   await new Promise((resolve, reject) => { ws.onopen = resolve; ws.onerror = reject })
   const errors = []
+  let loaded = false
   const pending = new Map()
   let id = 0
   const send = (method, params = {}) => new Promise((resolve) => {
@@ -56,6 +57,7 @@ try {
   ws.onmessage = ({ data }) => {
     const m = JSON.parse(data)
     if (m.id && pending.has(m.id)) { pending.get(m.id)(m.result ?? m.error); pending.delete(m.id) }
+    else if (m.method === 'Page.loadEventFired') loaded = true
     else if (m.method === 'Runtime.exceptionThrown') {
       const d = m.params.exceptionDetails
       errors.push(`exception: ${d.exception?.description ?? d.text}`)
@@ -69,7 +71,7 @@ try {
   await send('Log.enable')
   await send('Page.enable')
   await send('Page.navigate', { url })
-  await sleep(1000)
+  for (let i = 0; i < 100 && !loaded; i++) await sleep(100) // wait for the page load event (up to 10s)
 
   // Does the canvas hold at least one pixel that is not the #111111 background (and not transparent)?
   const check = `(() => {
@@ -80,8 +82,18 @@ try {
       if (d[i + 3] !== 0 && (d[i] !== 0x11 || d[i + 1] !== 0x11 || d[i + 2] !== 0x11)) return 'painted'
     return 'blank'
   })()`
-  const res = await send('Runtime.evaluate', { expression: check, returnByValue: true })
-  const state = res.result?.value ?? `evaluation failed: ${JSON.stringify(res)}`
+  // Poll instead of sleeping a fixed time: the first frame is drawn on the first animation frame after load.
+  const probe = async () => {
+    const res = await send('Runtime.evaluate', { expression: check, returnByValue: true })
+    return res.result?.value ?? `evaluation failed: ${JSON.stringify(res)}`
+  }
+  const poll = async (left) => {
+    const state = await probe()
+    if (state === 'painted' || left === 0) return state
+    await sleep(200)
+    return poll(left - 1)
+  }
+  const state = await poll(25) // every 200 ms, up to 5 s
 
   const problems = [...(state === 'painted' ? [] : [`canvas: ${state}`]), ...errors]
   clearTimeout(timer)