Well it's not bad for a start! I know how difficult it is to get started and I know how difficult it is to make a platform game without bugs. Maybe if you make the platforms thicker then the ball won't fall down. Also make sure that the lines of the platform are connected to each other (there can be invisible gaps).
I hope I could help! :) Don't give up!
Next time you should post unfinished games on Deviantart or another community where people could help you with your games, post critiques or they could even work together with you.
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