Decent!
Nice engine except for one problem, when I'm on the platform and then press jump followed by either right or left immediately afterwords the ball gets stuck. It says 'Gravity: 61' and it won't come down.
I'm not well versed with engines (atm) and the like but I'm guess you don't want that to happen?
I do like the double jump and the wall jump, they are well done. Also, I like how the ball slides down the wall when one presses the corresponding direction key.
One more thing, about your transparency GIF problem, if you used Photoshop to make the GIF then you have to make sure that under 'Index Color' (the first pop-up after you Save As...GIF) the 'Transparency' box is clicked off. I had that problem when I was making my 46x46 icon. D:<