COMPARE FAST · 20 TRIALS
Look at two lines and choose the longer one before time runs out.
Complete 20 timed comparisons. Wrong answers and timeouts count, then the game continues.
READY?
Use Left Arrow or A for left, and Right Arrow or D for right.
Keyboard: ← / A for left · → / D for right. Touch: tap a labeled button.
HOW TO PLAY
Start the game and look at both horizontal lines.
Choose LEFT or RIGHT for the longer line. The lines are never equal.
Finish 20 standard trials, or protect a perfect streak as endless mode gets faster.
LINE LENGTH TEST
Each trial combines visual size comparison, spatial attention, a two-choice decision, and a quick response. Standard differences become smaller in controlled steps.
This is a recreational browser game, not a vision exam or diagnostic assessment. Screen size, input method, attention, and practice can affect results.
READ YOUR RESULT
Standard accuracy includes all 20 trials, including timeouts. Average and best reaction times use correct answers only.
For a useful personal comparison, repeat the same mode on the same device and use the same input method.
QUESTIONS
No. One line is always longer. The difference narrows during the standard game but stays visually meaningful.
No. A wrong answer or timeout lowers your accuracy and advances to the next trial. Standard mode always runs for 20 trials.
Each correct choice adds to your streak. The response window shrinks, and one wrong answer or timeout ends the run.
Yes. Tap the two large buttons on a phone or tablet. On desktop, use the arrow keys or A and D.