AnimationPlayer

Timeline-based keyframe animation: track choice, RESET, root motion, libraries — scripts own recipes.

NEVER Do

NEVER forget RESET tracks — Animated properties otherwise stick across scene changes.
NEVER use Animation.CALL_MODE_CONTINUOUS for one-shot logic — Use CALL_MODE_DISCRETE.
NEVER animate embedded resource properties directly — Prefer instance uniforms / owned materials.
NEVER use animation_finished for looping clips — Use animation_looped or poll current_animation.
NEVER hardcode animation name strings at scale — Constants / StringName.
NEVER seek() without update=true when same-frame reads matter.
NEVER leave off-screen visual-only players active — Cull with notifiers.
NEVER mutate a playing AnimationLibrary — Stop / wait for finished first.
NEVER rely on speed_scale for long sync — Prefer seek() against a shared clock.