- Polygon asset type with per-vertex animation: new sidebar button inserts a
hexagon; vertex handles in the editor write per-keyframe `points` arrays
that interpolate between keyframes (requires matching point counts).
- Canvas mask preview: toggle in the zoom toolbar switches the stage
between the editable ghost view and a rendered view that applies the
actual masking via the shared canvas 2D path.
- Properties panel is grouped into collapsible sections (Transform, Text,
Appearance, Shadow, Mask) with per-section open/closed state persisted
to localStorage.
- Sidebar shape buttons are icon-only to reclaim width for the Polygon
entry.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>