great!
Great game! i finished your game whitout using the enter key ;)
the level 3 is the harder, but more turrets types will be interesting!
The level 4 is really good, but too short.
the w,a,s,d keys are not the betters to move. some keyboards are azerty or other (rare!), for a better gameplay, it will better if you let us configurate the buttons, or if you set the arrow keys to move...
It's really hard to play with an azerty keyboard! :D
But its really a good game! great job!