The frame rate averages at about 40 fps with consistent frame drops at large chunks of the stage, only drops to about 30, nothing too special. The game freezes up for a couple of seconds when you try to jump, but only in these large chunks.
The music doesn't loop correctly, but this can be fixed by using the in-game version of Metal Harbor instead of the copyrighted version.
The graphics are astounding, especially considering it's a WebGL game (on unity at that)
The game tends to eat up a shit ton of CPU for just jumping, like it just chokes, this can be optimized though.
I think you should add a script to the goal ring because it doesn't end the stage or restart the level and sonic seems to be stuck on something.
One last thing, I think the timer should be changed to an elapsed timer instead of elapsed ticks, just so it can be easier for players to read their time.
I'll also put this as a rating btw.