So here's a few things I thought could use some work.
- I couldn't play the game with sound, so it made it kind of difficult to know when I'd been hit. It would be a good idea to make the player flash red or something like that.
- The difficulty is uneven. I feel like the aliens that shoot at you should also have the ability to crouch and shoot or be able to run at you and hurt you. They just feel too easy without a different ability.
- The boss seems to be way harder than the level. While I found this fine I think a lot of people would feel frustrated. Maybe make a random chance for it's shots to miss completely?
- There are a couple empty rooms at the beginning that seem to be completely meaningless. I would do one of two things.
- Make them full of some sort of graphic that adds to the atmosphere of the game and leaves an impression on the player.
- Turn them in to some sort of platforming puzzle.
If you fix the gameplay up a bit I think you could actually have a foundation for a great game here. That would be awesome, there really isn't a whole lot of Construct games out there.
Keep up the good work! I hope to see another version of this!