Just about anything I could have said was said already by AmberFang. Game play wise he nailed what needed to be said, however there were a couple of things that escaped his very good review and were only minor in comparison.
One things I always seem to harp on in games like these are the music. While it's very dramatic and sets a good pace, it gets old quite fast. I realise you put in a mute button, however changing it up by having each tier of levels also have it's own melody would have prolonged the interest in playing this. The same could be said for the final boss whom I gave up on beating, lol. He deserves something to go with that horrific power.
The other would be something Amber passed over, but I felt needed a bit more explaining. It's easy to see where the silence spell works because of it's relatively large area affect, but the rest of the magic abilities seemed like a red wave here or there and then were gone. In the frenzy of the fight beyond level 7 those get lost quite fast. I know it helps to keep the frame-rate stable, but a pause here or there to SEE when I cast a spell would have also added to the feeling of "Oh yes, I should use this and keep from dying." It wouldn't need to be a constant or even lengthy show, just a quick wide glyph to recognize you were casting.
Just a few suggestions on my part that I hope can make it into the next game. This was fun, can't wait to see more of your work =)
Overall a great game. There are several issues, but doesn't effect it's quality. Good enough for me to play for 30 minutes. Maybe a bit too short?
The game opens up with a decently animated intro (by flash-on-the-internet standards) that provides our largely unimportant setting of science, magic, and some nebulous bad guy who we have to fight against. The setting is totally irrelevant to anything and feels tacked on more than anything; everything involving "magic" could have easily been explained with "science" and just seems like a poor attempt at originality.
The menus for the level select and the upgrade tree look nice and do the job well.
Basic gameplay is smooth: aiming works as one would expect and movement is good enough to dodge between bullets.
I do have to question some design decisions beyond that though. It would have been nicer to have a single continuous-fire primary weapon that didn't use "energy" rather than 2-3 sort-of-primary weapons that I had to switch between so the other could recharge. This is a huge problem because the weapon/ability selection is spread across the number keys at the top of the keyboard: I don't have a third hand to hit half of those buttons. And why even have the arrow keys as a movement option? You literally need 3 arms for that to work; this isn't an RPG or something. Players need all of the keys to be accessible.
I'd recommend you stick to WASD, 1234, Q, E, R, F, and Space if you want to make any sort of fast-paced game. WASD for movement, Q and/or E for swapping abilities, Space for special abilities, and you can use the rest for whatever.
Speaking of pacing, levels 1-14 are ridiculously easy: I scored 3 stars on all of them playing on Normal. Maybe it was because I caught on early to only being able to use 4-5 weapons/abilities at a time (including the space bar ability), so I jump nabbed all of the passives and steamrolled everything while ignoring the level hints.
Then comes the last boss which fires a barrage of missiles and spawns those whirlwind enemies among other annoying things, which would have been a welcome challenge if the rest of the game was paced properly to prepare me for the thing. It also doesn't help that the boss stomps on the "silence zone" circles so you don't have much of a chance doing anything against the whirlwind enemies that the boss spawns before your ship is sent crashing into the boss itself, doing an absurd amount of damage all at once. I will admit that I didn't actually beat the boss, but I'd have to say it's because of disinterest more than anything; I was already losing interest by level 10.
The enemy designs were pretty generic for the most part. The electric-fence generating ones were kind of interesting, except for that one level where there were swarms of them and it actually caused the frame-rate to drop. I would have expected something more after opening up with "Magic and Science," but all I really saw in the game was generic sci-fi.
Actually, just about the only thing resembling "magic" in the actual game was the Silence-Zone Spirograph, but even that just had the same function as an EMP attack. Heck, the only thing that wasn't some sort of robot were the sheep you could could turn the robots into.
Looking at the author's profile, I see that this is the third game that has been submitted to Newgrounds. I'm going to assume that the author is somewhat new, but that doesn't mean I had to be nice. What the author has here is a functional foundation, but the game that was built on it isn't that good. There's even some nice polish on the presentation, but that doesn't make up for the poor controls and bad pacing.
2 Stars: "Nothing too new or interesting"
But there's definitely potential for growth in future games.
Seriously, I started the game and i finished it one shot, great game!