Much like Metroid, with the same complaints.
Collecting upgrades, killing enemies and unlocking new areas. About 30 minutes of gameplay, but unfortunately, most of it is backtracking. Once you collect a powerup, your next objective is generally on the opposite side of the map, requiring several minutes of walking. Maybe in future games the checkpoint system could be used for fast-travelling?
The jetpack was an interesting addition, and genuinely fun, as well as cutting down on backtracking time. The map was fairly small, and not particularly helpful. I forgot it was there for most of the game.
The gun is satisfying. More power-ups for it would beinteresting, a variety of fire modes or just more power. Some enemies (the guardians in particular) take quite a while to kill, and have no attacks. Perhaps a visual indicator of their current health?
Overall, a short, fun game with some flaws and a great jetpack. Good job.
7/10.