Seemed well put together (although I didn't at first realise there was a double jump, and was cursing how accurate the jumps needed to be on the first screen!) but then... I couldn't work out what to do next. Walls with circular holes in may be some sort of door, perhaps? But I couldn't open it if so; "interact" didn't do anything, and I don't understand what the hub was for. The game seems well implemented and the shooting sound effect is nice, so I suspect the fault here is with me, but it does suggest that maybe some more helpful design might be useful?