Neat, I enjoyed trying it out. It's pretty hard considering the crabs' speed, but if you're good at defending during the first half you can pretty much just rest towards the rest, since the damage starts ramping up rather slowly. I also missed the point at which my HP stopped recovering automatically, but still made it to the end, with a score of, uh, 45 I think. Though I was just using 1 of each building type all along, I'd suggest having their descriptions on at all times, not just in the tutorial. All in all, I liked the gameplay concept, several difficulty settings and the simple yet pleasant to look at graphics. Nicely done!