Hi,
Thanks for the info.
I think that you're being too generous with the fast worker refund for the towers. Who is manning those cannons? I'd also be inclined to increase the workers required for towers and make them more of a strategic choice rather than 'quick, plonk down another tower', automatic decision.
A blood moon sounds interesting but if that was in the game I'd only be spamming out more towers to counter the possibility. It might work better if you created a second threat, one separate to the pirates. Give the player a reason to scratch his head and wonder if it's worth building another tower or, instead, putting the resources into countering the other threat. Maybe something internal to do with your approval rating?
At present the only impediment to your winning the game is a single threat (pirates) which can be easily dealt with (ring of towers). A second threat might open up a larger strategy space for the player and lead to more interesting decisions.
Cheers,
Plugger