Like the first guy said, your start button is cut off. I adjusted the game container using the inspector, and was able to get to stage 2. I can't see the door to stage 3, so I can't continue.
Should be an easy fix, which you can make in the "edit project" screen. You can either manually make the viewport the size needed to properly display your game, or add a fullscreen button so the game will scale up properly.
From what little I saw, you've got a good foundation for platforming using what I assume is a tileset. Collision is good, SFX trigger when they should, and you've got level switching down. If you have more complex stuff in later levels, I wasn't able to see it. Just adding the fullscreen button should make the game playable, so I'd recommend doing so.