Character is too slow. Especially considering that this game is obviously taking inspiration from Sonic.
Seeds = Rings.
Ants = Roboticized animals.
Rooster = Sonic.
S Hi T = Robotnik. RoNOTnick?
You should make him able to accelerate to higher speeds, and design the stages to better accommodate said speed.
The controls are unpleasant and floaty. You should make them tighter, more responsive, and faster.
Sound dips suddenly when Dr. Ronotnik speaks. You should have the volume lower and raise in a gradual triangle pattern rather than a sudden square, and it shouldn't lower to less than 70% volume. This is to make it subtle enough that the player doesn't notice the dip in volume to accommodate the voice. I'm not supposed to notice that.
Lacking fun factor. Though this could be a consequence of the controls. If you're going to emulate Sonic, then you should probably look closer at what makes it exciting to play. One thing I notice is that seeds are not exciting to collect in this game. Try giving them a little animation, and adding a subtle sound when you pick them up, so that they have a little liveliness to them.
I lost interest around the stage where you're trying to find a password for the doors. I just got bored. That's definitely not a good sign.
So my suggestions would be to take a closer look at games like the original Sonic The Hedgehog trilogy (study the game mechanics), Phoenotopia (study what makes it polished and exciting), and, I hate to bring this up again, since it's barely relevant, but I Wanna Be The Boshy, for its tight controls.
Aside from all that, I can tell you put a lot of work into this game. But the glaring issues prevent it from getting a really good score.