Good effort
Definitely one of the better games out here, good job on the effort. I have a few suggestions for the sequel you're making:
1. It was extremely difficult to cycle between weapons once you pick up too many. Since you allow people to specialize their skills for specific weapons, include a menu where you can toggle weapons that you want to have "equipped" so that you can simply switch between those few weapons at ease.
2. Explain what each weapon does earlier in the game because you give the player the option to put points into weapons that they don't even have yet. In fact, explaining the weapons at all would help, I had absolutely no idea of what the Buggun was for. It's also very difficult to tell which gun I'm currently holding -- make them different colors, at the least, instead of all blue.
3. More strategic battles! I cannot stress this enough. My favorite enemy in your game by far were the flying insects, because they were the only ones that didn't just mindlessly follow you so that you could beat them by simply running in circles. A few ideas that you might find interesting:
A) An enemy that cripples your Mecha a small bit by simply being alive in the map. This could be done in many ways: it could weaken your attack power, increase your reload times, or give the other enemies more armor. The goal is to quickly seek it and dispatch it. In turn, give it evasive AI and movement.
B) Enemies with varying movement patterns/defenses. An enemy who simply circles around you and fire shots, for example, or one who moves randomly and sometimes goes invisible.
C) Supportive enemies. Ones that heal other enemies, or otherwise help them in some way.
4. The interface could be improved. For one, a radar allowing the player to see the location of enemies that are not currently in his screen. When the Mecha takes damage, it should be more obvious -- a more noticeable "getting hit" sound effect, or the Mecha simply flashing red or something would be simply enough.
And lastly,
5. The last boss is too difficult or mundane to beat. The only viable strategies that I have so far seen are to either stay very far from it and wait for a shield powerup from the little spaceships (Mundane), or the player can choose to straight up fight the boss, which is basically impossible if the player has not upgraded movement speed or, in the case that I used, simply had an extra level saved up purposely for the "instant heal" upgrade. Make a final boss that requires more strategy and thought to defeat rather than strange strategies like that.
That all said, the artwork is good enough, and the sound effects are reasonable and within the mood of the game. The music could be a bit more exciting, but that's a matter of my personal taste. I look forward to seeing your improvements in your next game.
