here is a work in progress of my entry: Lakitu's Adventure
Sweet, a super mario shooter
It plays really smoothly. I like that a lot. I could see myself getting into this game.
But as an avid shmup player myself, there's some shmup no-nos you've done I'm afraid...
background is too busy, distracts from the enemies and makes it hard to see where your bullets are. Look at most shooters, the backgrounds are muted, simple and sometimes completely barren with just decorations on the fringes (think Gradius). In manic shooters, the priority is seeing things that can hit you and seeing your own bullets, which is why they are often a bright neon color.
Why does he throw the spikeys at different levels? I couldn't figure out what determined how he'd throw it.
The enemies come too fast for the rate he throws the spikes. Either increase the throw rate or decrease the enemy speed (again look at shooters, a shmup like R-Type, the bullets are slow but so are the enemies, a shmup like Dodonpachi, things are fast as hell, but your ship and bullets are too to compensate)
But I think you've got a really cool idea on your hands, I'll keep my eye on this one
EDIT: and a minor nitpick, I'd prefer the fire button be on the keyboard.