Key shapes are the proportional backbone of an icon set.
Circles, squares, rectangles. Each one defines how much space an icon occupies, keeping the whole set visually balanced regardless of how different each icon looks.
They work alongside the grid, not against it. And like the grid: they're guides, not absolutes. Knowing when an icon feels balanced takes as much practice and visual sensitivity as it does rule-following.
The shapes set the standard. Your eye makes the final call.
This gif here shows basic key shapes aligned to a 24x24 grid đ