clear grid before draw text

Author: codehz

index.html

@@ -367,6 +367,7 @@
 ctx.textBaseline = "top";
 
 const drawCharAt = (size, ch, x, y) => {
+ctx.clearRect(x, y, size, size);
 ctx.fillText(ch, x, y + yoffset);
 return (n => n > 0xF ? 0xF : n)(ctx.measureText(ch).width / size * 0xF);
 };