Artwork, Sound is good but the game idea is so basic and common, There is a thing in game that you can hold the left buttton of mouse and move cursor around your player in circular path this create an un breakable sheild around player which make game so much easy because enemy dies immediately on touching boomerang. You can disable this feature and only allow fire on click and you have to release button and press again to fire Or there is an other way that you can give enemy health bar which give some time to them to reach player even spamming around player in circular way. You also should add more feature like some coin system to buy some power our stuff like that...
overall view: This game Sound design is good, Artwork is also good. But shooting system make this game boring. Game idea is also so common and simple.