Is the fill measured by area or height?

Strictly by area — the game calculates the proportion of total shape area covered, not the height of the fill line.

Why does 50% look different on each shape?

Because shapes have varying cross-sectional widths at different heights. A triangle fills 50% of its area well below its visual midpoint.

What percentage error is considered a good score?

Within ±2% is excellent. Most players land within ±5% on regular shapes and ±8–12% on irregular ones.

Can You Fill Exactly 50%?

Can you fill half a shape — exactly 50% — by feel alone? Hold the button and watch the shape fill from the bottom. Release the moment you think exactly half is covered. Your score is the percentage error from the 50% mark. Easy shapes are rectangles where you can watch a clean linear fill; harder modes use irregular outlines where the fill rate accelerates and decelerates unpredictably.

How to Play

Press and hold the fill button — the shape begins filling from the bottom.
Release when you judge that exactly half the area is filled.
Your fill percentage and error from 50% are shown immediately.
Harder shapes have non-uniform cross-sections that speed up or slow the visible fill.

Why It's Hard

A straight-walled container fills linearly and is easy to judge. But a circle, for example, fills slowly at the bottom, accelerates at the widest point, then slows again at the top — making 50% arrive before the shape looks half full. Your brain calibrates fill speed from the current rate, not the accumulated area, causing consistent under-filling in narrowing shapes.

Tips

1For circles, the 50% fill mark is lower than the visual midline — release about 10% earlier than you think.
2Watch the fill rate: if it's slowing down, you're approaching the narrowing top and may already be past half.
3Practice on rectangles first to calibrate your "feel" before tackling irregular shapes.

FAQ

Is the fill measured by area or height?: Strictly by area — the game calculates the proportion of total shape area covered, not the height of the fill line.
Why does 50% look different on each shape?: Because shapes have varying cross-sectional widths at different heights. A triangle fills 50% of its area well below its visual midpoint.
What percentage error is considered a good score?: Within ±2% is excellent. Most players land within ±5% on regular shapes and ±8–12% on irregular ones.

Built by

Ethan R. Caldwell

Game Developer · Wilmington, DE

Designed Can You Fill Exactly 50%? and 46 other browser puzzles. Game developer based in Wilmington, Delaware. Hardcore puzzle gamer at heart — obsessed with logic puzzles, sokoban-style mechanics, and physics-based brain teasers. Off the clock, unwinds with ARPGs, RPGs and JRPGs.

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