maskStillDots method
Masks spaces between dots
used by under-layer effects like WormType.underground
Implementation
void maskStillDots(Size size, Canvas canvas) {
var path = Path()..addRect((const Offset(0, 0) & size));
for (var i = 0; i < count; i++) {
path = Path.combine(PathOperation.difference, path,
Path()..addRRect(buildStillDot(i, size)));
}
canvas.drawPath(path, Paint()..blendMode = BlendMode.clear);
}