HUNTER

When you hold down a key on the keyboard while in a textbox, you get a delay between the first and subsequent keys that appear. You don't want that delay crossing over into the movement of your ship, which it has here. You should handle "on mouse down" rather than "on key pressed" to move the ship, that way it won't be jerky.

Definitely agree with what darnkittydotcom said about the delay. But even after the delay is fixed the current movement value is too small to realistically avoid anything. Also the enemy speed seems to be randomized each time, it might make more sense for it to start the slowest on level one and get predictably faster with each new level.