Start/Stop: Spacebar (or tap Start). Respond with the matching arrow key, or swipe on touch devices.

• Green flash = correct; red = incorrect/timeout (one frame).
• Response window: 500 ms.
• Bits/sec uses mutual information:
  bits/sec = trials/sec × I(S;R), where I(S;R) is computed from the stimulus–response confusion matrix (including timeouts).

Tip: Click the canvas to focus. On phones/tablets, swipe in the arrow direction.