For every pixel you drew, finds the nearest target pixel, and vice versa. Both averages pass through a Gaussian curve — small misalignments still score well. Also applies a size penalty: drawing twice as large or half as small reduces your score logarithmically.

Intersection over Union. Overlapping pixels divided by all pixels covered by either drawing. Every pixel drawn outside the target inflates the union without helping the intersection, directly lowering your score. Even one extra stroke hurts.

Pure recall — what percentage of the target's pixels did you cover? Drawing outside the shape costs nothing. Good for learning new shapes since messy extra strokes don't hurt. Strategy: make sure you hit every part of the outline even if your lines are messy.

Each pixel inside the target earns +1. Each pixel outside deducts the penalty weight (0.25 light / 0.5 balanced / 1.0 heavy). Net total divided by target pixel count, clamped to 0. Heavy penalty means one wrong pixel cancels one correct pixel.

Instead of averaging distances like Chamfer, Hausdorff uses the single worst-misaligned point. It finds the furthest-from-target pixel you drew, and the furthest-from-your-drawing target pixel — and scores based on the worse of those two. One stray stroke destroys your score even if 99% of your drawing is perfect. No averaging, no mercy.

Measures how well your drawing's axis symmetry matches the target's. For each of four axes (horizontal, vertical, and both diagonals), the algorithm measures how symmetric both the target and your drawing are. Your per-axis symmetry is then compared to the target's and scored on each axis, weighted by how symmetric the target actually is on that axis.

A Star has high symmetry on all four axes — you must draw it symmetrically to score well. An Arrow or Flag has almost no symmetry — those axes carry near-zero weight so the algorithm falls back to the base Chamfer score, making it fair for inherently asymmetric shapes.

Strategy: focus on balanced, even strokes. A slightly smaller star scores higher than a lopsided one the same size.

Highest accuracy earns 1 point. Everyone else earns 0. Ties award 1 point to all tied players. Small accuracy edges matter enormously — 99% beats 98% the same as 99% beats 1%.

Your accuracy percentage becomes your points directly. 73.5% → 73.5 points. Everyone scores independently. Rewards consistency — scoring 80% every round beats 100% twice and 40% the rest.

Multiplies your accuracy by a factor based on how much time remained at lock-in. Max 1.5× if you lock in immediately. Exactly 1.0× at the buzzer. The live bar always shows base accuracy — the multiplier only applies at Lock In.

Rewards drawing the shape in as few strokes as possible. Each pen-down to pen-up counts as one stroke. Changes strategy completely — plan each stroke before committing rather than freely sketching. One precise stroke beats four sloppy ones.

Uses your highest accuracy at any point during drawing, not the score at lock-in. Draw freely, overshoot, refine — your best moment is captured automatically. Strategy change: you don't need to stop at exactly the right second. A small peak marker in the accuracy bar shows your best so far.