Five years ago, heck even 3 years ago, this would have been amazing. However, this isn't 2008.
I thought that your money earned/upgrade cost ratios were good, if not a little too good. I won the first time I played, and only was challenged when I accidentally figured out how to release more waves.
Are you color blind? It says (im paraphrasing) to place a turret on the green platform to begin. The platform was red. I will now profusely apologize if you are indeed color blind, or if I have somehow become color blind in the last 5 minutes.
Towers were nothing special, pretty much the same standard lineup for any TD game.
Badguys, well, the title pretty much sums it up... evil blocks. Im assuming that they are evil because they are attempting to make it though the gate... which is placed conveniently right next to their spawn point.... too bad they are to stupid to just pull a u turn and end it quick.
All in all there is nothing "wrong" with this game, and I found it enjoyable for the first 8 waves. Also its your second flash game.... so then I must say WOW!!! I cant make games for crap (just good at telling people how.... and that's debatable) so if this is truly your second game ever, then keep it up, and I will be sure to check for your future posts.
But that doesn't make this a better game.
It in no way what so ever stands out from the rest of the tower defense games.
Try making a unique tower. Maybe a back story, as to why these blocks are evil, and why I should care about them making it to the exit portal. Should I care because of something that's beyond that portal, like the city with my wife and unborn child that will be ravaged and killed if I let 20 blocks through?
The silence was deafening! you had animations for the "bullets" but no sounds! even a kepiew kepiew would suffice, and explosion or crumbling noise when a block is destroyed. Oh and while your at it a soundtrack too! (dont forget mute buttons!!! a pet peeve of mine)
A nice feature in many games that I did not notice was the ability to see what kind of enemy is in the next wave or two. It seemed like they were all the same, but i could have been wrong... also all your turrets are classified as "ground".... was there a plan for flying blocks? if so, and it was scrapped then remove the aforementioned classification, if not, then why was it there?
Ummm I feel like there was more, but I really wanna go watch some more Castle, so sorry if this seemed a little rushed, usually I try to catagorize everything so its not so disorganized.
Good game, good luck, I will be looking for further submissions!!!