A while back, I started trying to create a full jQuery/HTML/CSS game editor for a rpg style game. I never ended up finishing, but used it as a project to learn a lot more about how jQuery works. Try it out and see what you think!
Use the arrow keys to navigate. Space to Jump. And the action key is ‘v’. You can set actions on the action layer, add squares that are impassable with the blocked layer. And add a few landscape textures on the lowest and bg layers.