A suggestion on controls: make it two for both hands. Right (upper row) ASD and left HJK (lower). Takes a while to get used to, but it's much more comfortable than the default.
this game has a huge potential - with few updates it would be enjoyable for very long time. but the "pause" key is needed immediately, without it it's 3/5
Penguins were better, and, besides that, there already is a game based on exactly the same concept... Flying squirrel and getting acorns. I don't remember its name though...
 "Flaming Zombooka 2")
 "Reincarnation: The Backfire Of Hell")
 "PC.Defense")
 "Epic Coaster")
 "Punk-o-matic 2")
 "Bubble Tanks Arenas")
 "Civilian Killer")
 "Cover Orange 2")
 "MegaDrill")
 "Bubble Tanks Tower Defense")
 "Medical School")
 "Endless Migration")
 "Level Up!")
 "Fly Squirrel Fly")
 "Obey the Game")
 "RED CODE")
 "Infectonator!")
 "Palisade Guardian"){kind=logo}
 "Crush the Castle Players Pack")
 "My Pet Protector")