fun bug in kitsune tails today. sometimes people would clip through moving platforms that were going up and fall down under them. no idea why it was happening, virtually impossible to replicate

until i stepped through footage of it happening with an upwards crusher and i noticed the character was not stuck to the crusher but hovering slightly above it right before the clip. so clearly, they were jumping

i eventually realized that the collision checks if there's a collision with the top or bottom of your vertical collision box, and then pushes you up or down

but it also checks (for safety!) that you're moving up or downwards, so if the bottom half of your collision box clips a corner and you're jumping up, it doesn't suck you down onto the tile

this works great! except when tiles move. if a crusher moves up faster than the player, that check skips the collision, which puts you into solid geometry and spits you out the other side

fix was to also check if the layer is moving up or down, not just the player