Very fun game indeed.
~ Animation/Graphics ~
The graphics here were just about perfect. I don't think I would change anything really. Good drawings, good colors, good details, etc... The style of drawing was perfect for the game at hand.
Animation wise it was very good. I guess the only complaints was that when you went really high into space you would fall so fast and hit the ground so fast that sometimes you wouldn't even see the ground or anything on the way except for maybe a cloud or two.
When you hit a spike at certain angles your character would glitch from one place to another real quick instead of his body reacting to the area that he actually hit. The last thing could be the actual animation of the turtle himself. It could have been a tad bit better if you had animated some eye movement/mouth movement to represent screaming while he was being shot.
~ Story/Content ~
You had a lot of things to choose from here. You could buy a lot of cannons, a lot of guns, and other power ups too. The prices were just about perfect. It starts off taking a long time to build your money up, but it doesn't take too long to make people bored of the game.
The "enemies" on the map itself were pretty cool. I think that they were spread out about perfect. Not too far away so it was impossible to move and not too close so it could be too easy to keep going. The rare "enemies" sure were rare as I would have never known there was an UFO or Sun in the game if it wasn't for the medals.
I liked that you implemented the controls to move the turtle in the air while you are flying because it gives you some extra ability to pay attention to the game after your ammo has ran out. I think the best thing about the game though is that the medals don't make the game. If this didn't have medals I would still be playing it because it's a lot of fun. That being said the medals do make it funner though.
~ Some Random Tips ~
The game itself is pretty easy, but some people may still need some tips. Don't shoot your ammo like crazy. Time the shots perfect and you'll maximize the effect. The higher your character is falling from and the lower to the ground that you shoot him (before he hits the ground or it won't hardly be effective at all) the higher and farther the turtle will go.
If you find that you are having trouble getting some certain medals first make sure you are playing in Pop-Up Mode as this seems to take care of most if not all medal problems. If you can't find things like the suns or UFO's then just take your time and be calm. Check the userpage Wylina here on newgrounds for some tips for the game (and all the other games).
If you are getting frustrated that you can't get a medal just remind yourself that it's just a game, a fun game at that, and just play the game casually. You'll eventually get your medal as most of these medals are just luck. (The ones that you have to hit certain things)
If you notice that you're going to end the level soon and you are near some spikes then spike yourself for a small money bonus. If you are lucky enough you can get the never hit the ground money bonus by hitting an UFO before you get the ground or by hitting spikes in the air.
You can only be caught by UFO's if you are underneath it and get caught by it's beams. UFO's are actually not in space, but about half way from the ground/space. The suns are a tad bit higher. Jeeps are random, but if you stay low to the ground early you should be able to find one.
~ Audio ~
Sound effects were good all around and I loved the music. The ability to mute everything was perfect. I'm happy you didn't include something like screaming as that would be way too much noise going on at once. The usage of Mario sound effects were pretty cool.
~ Overall ~
A very fun game with or without the medals. It's worth playing and it's just one of those games that you can go back to play and play again if you're ever feeling bored. The ability to delete your progress allows you to start over and start the fun all over again. One of my favorite games by far. Good job on the great game. :)