Hey there. It's a good first step for the prototype. If you wish to imporve it the following aspects can be addressed:
- improved "skinning" for the character and the environment. There are many cute asset packs around to get you started.
- animations on the character and preferably on the surrounding objects.
- some "juicing" will help - like dust clouds on landing, visual special effect on a coin grab, death etc.
- progression could be faster. It's quite boring to wait while a coin is approaching me each time for a whole screen length.
- the jump height could be regulated by the time you hold a button. This way it would be much easier to grab tricky coins. Currently controls feel very rigid.
Keep it going!