Hey, you've got the basics almost there for a decent platformer. However the jump isn't high enough, arrow keys are not a good choice for movement as they also control vertical scrolling. The art is just copy pasted, the cactus is in the ground and has no hit detection (assuming that it is supposed to be an obstacle/platform.
You can't get to the higher platforms and most platforms are corrupted. Ultimately this game needs a lot more work done before it should be on the sight, I hope you continue working on your game.