Single player, by 
First upload by this user.
Let’s start with the positives:
For how linear and straightforward the level is, it actually looks pretty decent. The different layers are used pretty well, so even though you’re mostly going in a straight line, at least it doesn’t look boring or lazy.
Though it’s short, some areas have potential, as far as the layout is considered. Sure it still needs to be filled with some enemies and the variation of pickups need to differ, but it’s apparently a test level, so there’s that.
Now for the negatives:
Most importantly. Variety in pickups and item placement. Don’t just make a room with 8 large gems, and 4 weapon powerups. It’s like placing all the gems at the beginning of a Spyro level, so then you don’t bother to explore the level itself. The level is basically a continuation of rooms with a bunch of pickups, which don’t complement the decent layouts of the rooms.
Enemy placement needs to be improved. You only used normal turtles, but there are about 8 in the whole level, and half of them are in a straight line grouped up in each other (use the Stop Enemy function to keep them apart from each other).
The buttstomp and destructible blocks don’t work as intended, you shoot 1 and the whole row disappears (you also need to shoot the buttstomp block, though it’s irrelevant since you can jump over it).
All in all, there might be some potential here. Some of the issues are easily fixable (item & enemy placement), while others may need some practice in the level creator to learn (what functions each event has)