Even though you mention the issues of overscoping, what is there is definitely very polished: Controls, aliens, opening and closing of doors, spawning, sprites, etc. I can absolutely relate to the habit of perfecting one area while leaving other things for last, lol. But this mindset hurts when it comes to the existence of deadlines.
The best way to deal with this issue is doing a simple "pros v.s. cons" analysis: "Does perfecting this feature matter more than not doing anything on this other feature?" For example, in this project:
- Do the cool 3D-esque head movements of the robot matter more than adding sounds?
- Or... Does the intro of humans running (and getting infected once you lose) matter more than adding variation between the different aliens (like more health and lower speed for the bigger ones, for example)?
While the ideal would be to have all of these, some are more important than others (this situation becomes further intensified in jams!).
Regardless, you now know both your abilities & limits better, and that's really important!