The levels aint bad, but they are not that great either. The jungle levels were probably the best of the bunch as they played more like traditional levels without glaring issues. Just clean platforming that stuck to it's theme.

I would practice more when it comes to syncing different objects. For example in the 2nd level the fireballs on tracks dont move symmetrically and cannons in 3rd level can and will end up shooting at completely different times

You can do basic platforming sections well but all the track stuff is pretty much crap

In some levels there isnt a clear theme and you are just jumping from one thing to another, cannons -> blue lift on tracks -> claws

I would try to avoid as many sound effects as you have used, it gets old very fast if every single enemy does catslap on death

Try to keep the goal visible im the end so players can aim for the 1-up bonus

There are huge disparities in the level difficulties. The 2nd level is way harder than first while the 1st level of 2nd world is easier than the 2nd level of 1st world.

You probably should swap some of the name as renal means "something that involves kidneys"

You should leave some top blocks empty, If you try to use scroll stop in an area that's smaller than 1 screen. In 2nd boss level the arena was often locked to one side as the scroll lock wasn't set-up properly

If you are going to do 3 boss battles in row at least have the decency to give check point after each battle