Hi there! 2013, dang, you've been on it for quite a while. Got to respect that! I reckon this post will come as a surprise looking at the activity
First off, I appreciate the overall solidness of your project. The game feels bug free and very responsive. I can see you have put a lot of effort into the project, it features everything that classic games used to feature. It has that whole package: consistent graphics, interesting backgrounds, solid run & gun gameplay and pretty cool bossess. The unlockable weapons were quite nifty too, I like the phaser shot that phases out enemies (or what was the name?). I definitely had fun playing through the demo.
The game was not without its problems though, so here's my two cents.
Presentation
Looks good, especially your attention to the backdrops. Good use of isometrics there.
Though I have to say that I'm not too keen on (some) of your character designs. They feel ordinary and lack expression, in particular the aliens and the main character. However your boss designs look tight, especially that big robot boss which was (easy) yet awesome. I had a good laugh at the gore and the eye for detail like the little bugs that you can squash are sweet. It felt satisfying to shoot those enemies dead.
Where I like the design of your tilesets it's hard to distinguish which one is actually 'walkable' and which one is not (i.e. train level). As a player you feel cheated once you fall through a platform that looks walkable. Maybe shading them a'little would help.
The story was a good addition in the sense of carrying the progression of the game, yet felt very standard and ordinary ('kill those terrorrists!'). It's not a major problem as these kind of games are mostly about the run & gun gameplay but I think the story could work out better if coupled with more motives and lore, accompanying the characters and thus creating 'expression' as a result.
Audio wise, pretty good! Not sure if you did the music yourself but it fits the retro aesthetics and is of quite high quality. Good mixing/producing there.
Same for the SFX, nothing real fancy but they fit the animations and game events good enough.
Gameplay
Simple yet enjoyable. I think it's a nice touch that the game starts out as a shoot 'm up and then transitions to platforming.
The platforming itself is solid but lacks any form of originality. Some of your level designs were kind of annoying platform wise (especially in the desert with the small vertical platforms which you cannot jump though).
Shooting is fine. Nice touch with the ducking and the enemies that stay in cover, where sometimes different weapons work better in different situations.
Overall it is an enjoyable and solid project, but I feel it lacks originality to really stand out. What is that
one thing that your game has and others do not? It feels real standard, from the story to the characters to the gameplay. Other than that you did a terrific job tailoring the different aspects of making a game. Good job!