Answer 1

On my devices (ipad, android phone, desktop) it looks as if the canvas has been zoomed in, along with the dots appearing off to the right of the point where I touch the screen.

Lines 15 and 16 are causing the problem.
canvas.style.height = (screen.height - gapY) + "px";
canvas.style.width = screen.width + "px";

Instead of canvas.style.height/width you should use canvas.height and canvas.width

https://code.sololearn.com/Wyr406XbqLa3

Answer 2

I also noticed that issue...
Maybe that is due to the dot size...

Answer 3

You are very welcome. Keep up the good work!

Answer 4

yeah it's very compiler