Answer 1

After nine minutes of painstaking dust cleaning I gave up.

Please do not put dust on the ceiling like this. Also the giant slime room kinda works if it was 10 times smaller.  also a lot of your dust slides you don't clear all the dust by running over them.The red flag connected to an enemy or the purple flag with an area selected will end the level.

Also the whole thing is way way too long.

Answer 2

Way too big and too much dust everywhere, even if it had an ending flag, there'd be no-one getting an S/S here. Try taking a cue from the official levels and use dust as pointer, not as decoration.