ARE YOU READY? ACTION
First, I don't see the need for the recharging star meter. The biggest issue that a Sonic game should curb is forcing the player to stand still and wait for something to happen.
You can always move around when you land, and when you do land you're given an extra 'pity' star if you ran out. A good way to play Jasper is to hang onto stars and recharge while you make your way through an area that doesn't require shooting anything anyway, such as a normal hallway.
Lastly, and with some trepidation, I must talk about the character's appearance. I don't have a way of sugarcoating it, so I'll just come out and say that Jasper is not an appealing character design to me. He kind of looks like what you'd get if you mixed a typical Sonic fan character with Kirby-esque simplicity. It leaves him looking a bit like a slime creature with white accents.
i can assure you jasper isn't made out of slime
Jasper himself isn't very well defined design wise and I agree that the mix of simplicity and typical standards can make him look really... bleh at points. The sprites really show this bleh factor off, especially with the muzzle and the fin of the hat. The fin actually rotates with Jasper somewhat like Mickey Mouse ears so there's that. I'm not upset that someone didn't really enjoy with how Jasper looks and I'm kinda glad someone did speak up about it.
Lastly, and I apologize for ending on another criticism, but the pink star effect for the spin-dash is way too big. It's a neat effect, but it obscures too much of the action onscreen. If it was just a little smaller, and maybe a bit more transparent, so that Jasper can be seen from within it, it'd be perfect.
I had a big brain fart moment over the spindash trail. The spintrail itself spawns ghost objects and it became tedious to manage how thick the spintrail works with how long the object lasted for. I did experiment with a more transparent trail and I didn't stick with it as a last minute thing. I'll probably consider making it more like regular spintrails, being much more transparent.