Alright, so, I’ve got an idea, which, I’ll admit, may not fit the theme entirely, but it works:

Evolution of a fisherman!
so essentially, the concept is you start off on a very small boat, with little to no ressources, and the goal is to sell fish to buy stuff for you boat, all in the mindset of evolving into the master fishing boat!
all that while defending against the onslaught of pirates and storms who may very well sink your ship, making you lose all your precious cargo…

So yeah, really, focusing on evolving that damn boat into an iron-clad-cannon-flinging-harpoon-epicness that will still fish fish (and maybe steal fish as well, will have to see…)

mock-up cause I love ’em: