prevent duplicate writes

src/server/object/canvas.ts

@@ -37,6 +37,12 @@ export class Canvas {
 
     const color = typeof pixel === 'string' ? storeHex(pixel) : pixel;
     const index = to1D(x, y, this.size);
+
+    // prevent duplicate writes
+    if (this._canvas[index] === color) {
+      return;
+    }
+
     const record = {
       user,
       color,