Synfig Studio
An open-source 2D animation package with bones, deformation, keyframes, vector layers, and procedural parameters.
Why use it
Tweening reduces frame-by-frame drawing for cutscenes, character parts, moving backgrounds, and promo prototypes.
Where it fits
Use art, animation, audio, levels, and narrative to make the game easy to read and its world convincing.
What to check
Its interface and render pipeline take adjustment; engine delivery usually requires baked frames, video, or custom data.