Spacebar Reaction Time Test
Same test, react with the spacebar — your keyboard hand vs. your mouse hand.
Is the spacebar really faster?
A keypress lands a hair sooner than a mouse click for most people. Key switches actuate partway through their travel, and the finger already resting on the spacebar scarcely has to move, whereas a click asks a fingertip to press down through a full switch. Small as it is, usually 5 to 15 ms, the difference is real and measurable.
The rest is the classic test. Through a random 1.5 to 5 second delay the panel stays red, then flips green, and a clock started at the exact frame your screen painted that green stops the instant your key goes down. That happens on keydown, not keyup, so your own key-release time never reaches the score.
Five runs, median taken. Run the classic click test too and your stats page will set the two medians against each other, so you can see your own keyboard-versus-mouse margin instead of taking ours on trust.