I decided to make a 1s1s game. The stage is never used, all levels and the thumbnail and the player are contained within 1 script inside 1 sprite. Arrow keys to move. There are 10 levels in total. DO NOT PLAY IN FULLSCREEN! It ruins the quality. How this works is that before every level starts, the Scratch Cat goes to full size, changes costume to the correct level, and stamps an image of itself. This creates the level. Then, the Scratch cat goes to the correct level starting point (held in a list), and starts the platforming script.
Credit to @griffpatch for the Scratch Cat animation. Platforming script is a mixture of @djpro 's and @griffpatch 's platforming script (confusing, right?) The reason I had to mix them is that djpro's script didn't have very good wall jumping or animation, but griffpatch's script had lots of custom blocks, which would have ruined the 1s1s bit. So I squashed them together into a very glitchy platforming script. Use it if you want.