Overlay

Overlay is a focused clone of the core Figma/Excalidraw experience: an infinite canvas where multiple people draw, edit, and see each other's cursors in perfect real-time sync. No accounts, no backend to sign up for — it runs on your machine.

HIGHLIGHTS

• Infinite canvas with smooth pan and zoom-to-cursor on a custom requestAnimationFrame loop
• Seven tools, multi-select, 8-handle resize, group rotate, snapping with alignment guides
• Live interpolated cursors, per-peer selection colors, a shareable board URL
• CRDT sync (Yjs) with per-user undo; local-first persistence to IndexedDB
• Export to high-res PNG or SVG; light/dark, touch, keyboard shortcuts, reduced motion

HOW IT’S BUILT

The whole thing sits on a hand-written HTML5 Canvas 2D render loop — no canvas or whiteboard library — that only redraws on change and holds a steady 60fps with 500+ shapes while a cursor is moving. Collaboration is CRDT-based (Yjs): shapes sync through a shared document, undo/redo is scoped to your own edits so you never revert a collaborator's work, and the board persists to IndexedDB so a solo reload keeps your work even offline.

STACK