yeah overmasking is _definitely_ fixed, works great now

js/index.js

@@ -646,6 +646,7 @@ function mouseUp(evt) {
 							initImgData.data[i + 3] = imgChunkData[i + 3]; //it's still RGBA so we can handily do this in nice chunks'o'4
 						}
 					}
+					if (overMaskPx > 0) {
 						// https://stackoverflow.com/a/30204783 ???? !!!!!!!!
 						overMaskCanvasCtx.fillStyle = "black";
 						overMaskCanvasCtx.fillRect(0, 0, drawIt.w, drawIt.h); // fill with black instead of null to start
@@ -658,7 +659,7 @@ function mouseUp(evt) {
 								overMaskCanvasCtx.arc(
 									(i / 4) % overMaskCanvas.width,
 									Math.floor(i / 4 / overMaskCanvas.width),
-								4 * scaleFactor + rando,
+									scaleFactor + rando, // was 4 * sf + rando, too big
 									0,
 									2 * Math.PI,
 									true
@@ -674,6 +675,7 @@ function mouseUp(evt) {
 							overMaskCanvas.height
 						);
 						overMaskCanvasCtx.putImageData(overMaskImgData, 0, 0);
+					}
 					// also check for painted masks in region, add them as white pixels to mask canvas
 					const maskChunk = maskPaintCtx.getImageData(
 						drawIt.x,