After much turmoil, I did manage to complete this. The collection of the wechiles to progress was _tortuous_. I didn't get the fifth key until my 5th box ;_;
All in all, I like the concept. I think there's room to improve with the pacing , but the groundwork is great. There might be an opportunity to add a leaderboard for how fast you progress, or some such.
I didn't manage to kill all of the enemies in the final room, I just skipped past them to the Captain. I was losing health far too fast and have terrible aim.