Not suggesting any big things here... All I propose is to have the options for toggling the canvas overlays (empty canvas, heat, template) directly within the canvas editing screen instead of putting it in the sidebar, kinda like Google Maps. I think the sidebar version would be preferred in mobiles, so you could make this desktop only.

Alternatively, you could allow the user to place pixels on the canvas even while the sidebar is opened, like the way it was for the first 48 hours of the event. Also ensure the right side of the color palette is not hidden by the sidebar.

Suggestions:

• When getting rid of bots, undo their changes.
• Assign the pixel timer based also on IP, not just account. That should discourage people who used multiple accounts just to have more pixels.
• Don't let freshly created accounts to place pixels. They compound with both issues above.

I would suggest a small countdown to the end of the event on the place where the pixels count and coordinates belong (circled below), only displaying during the event.

An extended undo functionality would have been handy sometimes. Like, having an eraser that would revert any pixel I have placed myself (and that is still visible) to what it was before while adding one to my pixel store until that is filled. That way I would be able to move or correct things without having to wait (possibly twice as long) for the counter.