I got to wave 17 before two of the big red guys distracted me long enough for a little guy to sneak through (I didn't even see him get in! Probably because I removed my glasses...)
Final score: 10391
Anyways, back to the review.
Overall, it was a pretty well-built game. I liked the controls, and they way you combined the cannons into one control was ingenious and added a little extra difficulty (though I never bothered actually positioning the two other circles)
The graphics were excellent, fit the theme, and accurately projected information to the player. The sounds were good, but could get repetitive. Some more variety in music would have been a good addition. Perhaps even some grunts or random outbursts from the enemies, too.
The upgrades could have used more explanation. Most probably assumed they increased damage, but (I believe) they actually increased the damage splash range. More upgrades would have been nice. As one reviewer mentioned, maybe upgrading wall strength, or adding traps--you have plenty of map to work with, especially the beach area! It didn't take long for me to run out of things to upgrade and for the gameplay to run dry because of it.
Lag was another issue with the larger enemy charges. I would work on optimizing the sprites or AS (I couldn't tell which was causing it).
Overall, a great game considering it was just put together to advertise another game. I don't expect you to read these reviews or continue to improve the game (I imagine you have better things to do), so I'll end it at that.
Tips to other players:
Focus on getting critical hits by firing exactly when the cursor turns green, as they do much more damage than regular shots. However, don't be afraid of just spamming the lower level enemies. Here's of list of what it takes to bring them down:
Basic foot soldiers: 1 Regular hit
Basic Arches: 1 Regular hit
Hammer soldiers: 1 critical hit
Crazy power charging soldiers: 1 critical hit + 1 regular hit
Big red guys: 5+ Critical hits (I didn't bother counting, but don't waste your time hitting them with non-critical shots)
Here's a trick:
If you time it right and fire just as the cannons finish cooling down, they'll launch another critical shot instantly. It's a bit tricky to get, but can take down enemies fast!
Good luck!