Additional human tweaks:
- save level scores so that you can replay levels and improve
>>> Prompt:
Given a canvas and requestAnimationFrame(update).
Give me functions to fade in and out HTML element "canvas" on command
from update(). The command is a global variable called "fade" which
can contain "in", "out", or null.
You have the following timing variables available:
lastFrameUpdate = currentTime - (currentTime % frameInterval);
I don't need explanation this time, just give me the code.