Thank you for playing it! It definitely can get difficult as time goes on and more ships approach. I feel like some improvements to the combat such as a targeting camera could make it feel less daunting. I tried limiting how many foot pirates could be on the island at one time to 5 to try and ease the difficulty.
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Limiting the pirates might be a good way to tune difficulty. And the targeting camera you mentioned might also help. If there was a way to scale the pirates more over time where for the first several minutes you were fighting just one or two. Then once you've figured it out the difficulty ramps up? Something like that?