Do you have an android or ios demo I can try?
Is there sound included or how hard is it to add background music and sound effects for someone new to construct 2.
Since you seem open to suggestions what about ability to get powerups or items (like in super mario where he can change to shoot fireballs and such). Or the ability to start with no weapon and to pick it up along the way.
By the way, what is coins for now? Can you buy anything with it in the game or is it just to collect?