as glodefunk said the controls are very difficult so if you moved with aswd/arrow keys it could be a very good game with a bit more upgrades and maybe different levels or something you have a very good start just keep working on it and you could probably have a 4 star rated game.
i think the helicopter should just randomly choose a place to shoot because as of now the misses rarely ever hit the ground because when i kill the enemy before the missile hits it the missile dissapears .