The attack button is actually a joystick. You don't have to tap it to attack enemies, but move your finger in the direction you want to attack. Unfortunately we can't change the joystick to a classic button, but we're working on an optimization so that the first shot is easier to control and doesn't go off in a random direction. It should be live in the next update !

We know this is a bit tricky, but you'll quickly become used to it!

Mind you, with some characters, you can't move and attack at the same time.