Not bad!
However, due to the tidious backtracking without change (except some new enemies spawning from time top time) the replay value is rather low (I wont try it again now, although I am curious what the plasma cannon is that was proposed to be unlocked at the end of the game). A few warp gates (that are inactive during challanges), maybe with limited usages, would easily solve this!

Seems like I missed a room, I couldn't find all enemies or their drops, although I finished the game.

Finishing the game doesn't allow you to search the whole game for secrets, because the game ends. Instead, put a menu at your rocket (leave? = end game) once you brought the parts there. This way we can try to discover missed stuff.

I'm with jrl80 - where in the heck is the 7th butterfly?? (for the hyperdrive upgrade)
Have been all over the map - all enemies have been killed. Tried to get back over the lava pool but I die each time (even with 5 hearts - that didn't happen when I did it earlier). I can see *something* flying too high for me to reach in the screen next to the hyperdrive upgrade.. don't think it's a butterfly though.
Also agree with prev comments re: laser & map. Without a few hints, made it tougher than it needed to be. But the game itself is pretty good.

Edit: jrl80: I had to start over; somehow I ended up with 7 butterflies this time, and finished the game. Phew.

Beat this game but it was very frustrating. I wouldn't have known what to do with the broken gun without Trixter's comment. Also make sure you go past the lava pool before u get lava resitance or you wont be able to go there, you can beat the game without it though.

I can't find the last butterfly!!?!? I've run from the volcano(?) to Oscar Splendid and back to find no more enemies.

You know.. I was really enjoying myself.. I had just gotten my waterproofing and went for what I had thought was a secret (a wall I had walked through and died earlier. It led from the first passage in the castle to the underwater area... well. it turns out it was a glitch/bug.. not a secret passage. I fell off the screen and didn't die (waterproof you know)... Because there is not any command to restart from a checkpoint I decided to save and close hoping to get respawned at the last checkpoint.. no such luck.. I am guessing I was almost done with the game.. so I am probably not going to bother re-playing it even if that is fixed.. Kind of annoying, Other players reading this.. that is not a secret passage...

Other comments on the game. The way the game is set up you literally spam the enemies to death with your own lives.. It is the only way to do it, because up until you get the grenade and the functioning laser you can't really do much else. And even then it is often easier to just attack and deal with the respawn. Granted you have infinite lives, just a pet peeve with me. Even in a game with infinite lives I think it should be possible to play well and and get through with minimal or no deaths.

It would be nice to have some kind of global map, with 'locked' or blocked passages marked to make it easier to recall where you still need to go.

I suspect there are some other glitch zones as well. In the caves one of the dark blue shooters (I don't know what to call them) fell into something that looked like floor. I am guessing there are probably other holes in the world, and because you do have secret areas people will be looking for such holes.. just make sure to remove any deathtrap holes in the world.. or rather non-death game-breaking-trap holes..

Another thing is the items that you get off of enemies, it would be kind of nice to know what the heck they are. This is more of a pet peeve than anything. Maybe just add a text pop up such as "You collected a lens" or "You collected a beetle elytron. enough of these could improve your push attack".. something like that. What are the little black balls coming from the spiders.. I don't know..

One point where it would be really useful to give us more info is the laser. I ran around the map like a dumbass looking for more eyeballs to get lenses from because I thought the laser was literally broken. I only accidentally had it on in front of the breakable stone and found out it was still useful at that point. On those lines it would be nice to just have a popup letting us know what is stopping us from getting through certain barriers.. I guess that goes to my peeve against spray and pray.

Overall though it was a good game and I did (despite some frustrations/annoyances) thoroughly enjoy myself. It is just a pity I can't finish the game without restarting from scratch.