Remove `set_pixel` and replace it with something else

[LittleEndu]

I feel like directly setting a pixel is getting boring and having to figure out some other algorithm would be more interesting. One idea I had was to replace set_pixel with something like set_pixel_channel but with a catch. The channel set is the channel with index (x + y) % 3. This would pair excellent with the swap_pixel idea as the most optimal algorithm isn't immediately obvious.

[ChrisLovering]

I am closing this issue. We will be doing something different for the next event, but that will be planned in secret, as to not spoil the fun!