Our 2D game character grew 3% taller every time he walked

Summary

We’re working on an adventure game, Leonardo’s Moon Ship. The player character, Leo, has the usual pile of animations: idle left and right, walk in four directions, a couple of stair anims. Since implementing the basics of the character, Leo has had this slightly cursed behaviour where he’d grow about 3% taller the moment he started walking, then shrink back when he stopped. His feet would also lift off the ground by up to 27 pixels depending on which way he was facing. Not enough to be obviously broken in a screenshot. Exactly enough to make the game feel wrong. That’s the bug overlaid on itself. The red ghost is the naive setup. The blue is the fixed version. When Leo’s idle they sit on top of each other. The second a walk anim kicks in the red drifts up and out of place.Why a single scale falls overThe animations came from the artists on wildly inconsistent canvases. Not the character, the canvas the character was painted on. Here’s the actual sizes:idle_right: 675x1095, character tight-croppedidle_left: 616x1094, basically the same character, slightly different cropwalk_right and walk_left: 1920x1200, but Leo himself is only about 700x1088 and floating somewhere inside all that transparent spacewalk_up: 664x1202walk_down: 664x1202This is normal. Artists work in whatever canvas size makes sense for the motion they’re drawing. Walk cycles need horizontal room for the stride, idle frames don’t. And good luck enforcing a single canvas size across hundreds of frames and constant revisions.The naive setup was a single animated-sprite node with one sprite_scale of 0.28 and one feet_offset_y of -340 applied globally. That only works when every animation has the same character pixel height and the character sits at the same place inside its canvas. Neither was true here. The walk_right character was about 305 visible pixels tall, idle_right was 296. Multiply both by 0.28, and one renders three pixels taller than the other every time Leo stops moving. And because walk_dow...