Platformer Jump is a great block-based platforming game. Use the arrow keys to move. You can make levels with the level editor, name and share them. For more instructions, go to the /help page. The homepage gives you a random level. Try to get to the top without hitting the color red!
@Gopher Thanks for the feedback! If what you mean by levels is user-created arrangements of blocks, those do exist. You can see all user-made levels by clicking the 3 bars at the top left of the screen, then clicking "All levels". Here's a link to one of my favorite levels. The goal of every level is to either reach the top of the screen, or to touch the green block.