Buttons for "pause" and "next wave" would have been a nice luxury, but even without them it still wasn't terribly frantic.
There isn't any sort of data on the towers or attacking ships; that's okay though, because strategically, you can ignore the outer two forts and use the island space for spamming treasure chests. Then, build a bunch of skulls on the middle track. I got to wave 40 on my second run through with this strategy. Nothing too complicated, but a fun game for a few dozen minutes; certainly beats the hell out of most of the other games available for free.