Super Mario fangame (first engine demo)

[Zero Kirby]

Not bad, now this is what fangames need to do : aim for quality. You've got here a very good engine.
Some points however.

The slippery ice wasn't bad, but make it a bit more slippery.
The water was a good touch, though I say you shouldn't be able to move as fast in it as you do. After all, if you've ever been swimming, there's a lot of resistance when you swim. Mario should have a bit more trouble in the water.
Are you able to pick up the turtle shells or not, I couldn't tell.
Finally if you hold an arrow direction, jump into a wall and land, you still have the jump animation. I found this out at the part with the yellow blocks below you and you had to spin jump to go down.

The ice wasn't slippery enough? I thought it was TOO slippery! I guess I'll have to wait and see what other people think. (I've already made it less slippery, but still slippery.)
I can fix the water movement, though.
You can't pick up Koopa shells. Sorry.
As for the animation glitch, I just checked, that's actually just the walking animation. I should probably still fix it, though.