Good variety of traps and hazards to overcome and build in levels. Good level editor. Many creative and fun levels.
Many bad levels too. Some so amateurish that they have no place in a professional product. Level difficulty progression very haphazard, with moderately hard levels at start, and many trivially easy levels later. Levels should be curated better for quality and progression.
Unknown purpose of collectible coins, since game doesn't keep persistent record of them.
Many levels require pixel-perfect positioning, but player movement is slightly too jerky to suit this level design. Jumping, falling, and walking need acceleration adjustment to suit levels, or levels need to require less precision. Levels are playable as is, but often feel awkward with current movement.
Player can exit visible level area, which feels cheap and unprofessional. Many levels require player to exit visible area by jumping above the top of the screen, which is very wrong. Visible screen borders should be made solid to the player character, and levels redesigned to account for this.
Annoying how player slides quickly down ladders unless climbing upward. Automatic slide down speed on ladder should be slower, similar to falling speed in water, but not as slow to differentiate their functions.