I think this game has lots of polish in good places, and what it needs now is some input and physics tuning to be more fun. A very popular web game early in the 2000's was a 2D chopper game where you literally just clicked to go up otherwise fall down. This game feels like it has way more potential but needs some tuning.
I don't think the helicopter should just stop moving when fingers off the inputs, it should have some momentum. Acceleration and deceleration should be a thing because they would make gameplay more dynamic.
Otherwise I think what would be good is a more gradual intro to NPC's/enemies. I think the majority of players are getting pretty clobbered in the first few moments as is. There should be some time in lvl1 to test the chopper and see how to manage enemies in smaller encounters, graduating to more enemies at once.