Feedback: It's a fun game but I have some suggestions. (Maybe for your next game!)
Lots of people have mentioned issues with the key layout. Since we switch character more often than we build, I don't think it makes sense to use Shift when switching character. We could put characters on plain 1,2,3,4, and for building/launching we could use Shift-1,2,3,4 or 7,8,9,0 or letter keys.
Sometimes I wanted to bring the character to the part of the map I am currently looking at (e.g. to meet up with a crew mate). But as soon as I select him, the camera moves to his location! One solution to that might be: Tab always jumps direct to the character's location. But when pressing 1,2,3,4 to select a character, the camera selects the player but doesn't jump to their location. Then I could press 2 and right-click, to bring the character onto the screen. If the key is pressed a second time (when the character is already selected), then the camera can jump to the player (e.g. by pressing 2, 2).
I found the difficultly ramped up a little strongly at first, but then it became too easy. The first three games I died very quickly on levels 2, 3 and 4 respectively. It felt painful to be slaughtered so quickly after landing, and then sent all the way back to the start. (The first level is a bit slow to keep repeating.) Basically I wanted the chance to retry the level. (Funnily you can replay the level, but only if you quit the game before the ship is destroyed!) Some arcade-style games used to allow 2 retries, and I think that could work here.
On my fourth play I understood the game better (and maybe had some luck), and I realised I could go back to earlier levels to stock up, so I slaughtered the creatures and completed the game! Perhaps having easy, medium, difficult modes could make it less painful for beginners, but add extra challenges (and secrets) for players who want to keep coming back.
I found my cannons were a bit weak. If I left them alone, they would quickly get destroyed before I could run across the map to heal them. (So my tactic was to put cannons beside the ship, and keep an engineer at the ship at all times. A bit boring!) Perhaps if the creatures did not attack the cannons (or only did so briefly) then I could be confident to place them anywhere, and they would work more like a tower defence, shooting at creatures as they pass by (and needing only occasional healing).
I was sad at the end, because I thought I could land in the wormhole. I thought I had one more location to play, but no, the game just ended on me! Perhaps make the wormhole look less like the landable planet locations. (E.g. make it larger, and not round. Don't label it like the planets are labeled.)
Anyway it was a cute and fun game to play overall. I enjoyed it. Thanks for making it!