The indie platformer Gateways today added Steam Workshop integration for easily sharing custom levels. The game's integrated editor lets you create your own puzzles and quickly share them with the world.
Or, you can browse around and find levels created by other users to play.
Grab the gateway guns and explore a huge lab filled with mysterious puzzles in this classic platforming adventure. Use gateway technology to leap from one place to another, change size to explore small passages or defeat large enemies, walk on walls and ceilings to reach new areas and even travel in time to work together with past echoes of yourself.