Thanks for the feedback. I wanted to keep the game short and sweet so I could actually finish it. Your right a lot of things could be easily expanded. The revive item is single use as far as I remember. I could always make it more expensive if it's too broken, but I didn't want the game to super hard anyway. I thought about a speed upgrade, but never implemented it that's a thing I could note to add.
I think the pacing is good because I played through the game like hundreds of times and adjusted things to what felt right. I wish I had added more to the ending but at a certain point I had to stop adding new things and start finishing what I had. I think you can only send One person through the portal but maybe there is a bug. I was wondering if it was easy to figure out the puzzle at the end of the game, with the wave forms. I thought it might be a little obtuse, but coming up with a puzzle is hard.
If I do go back to it I think I will convert it to Godot 4, and while I'm at it I can fix somethings and add some more, like a better ending. I did have an alien sprite that was going to show up at some point and join your crew. Maybe the astronaut you send comes back with an alien friend.