0.2.0 is up, thanks to all of you — every point below came from this thread.
Oil now actually costs something: it's a currency you spend on upgrades. The lantern refills each night (that's a separate gauge), so ship oil finally has a purpose. Good catch @Skruntoo, that was a hole I made myself.
Tank levels stay useful to the last one: a longer and wider beam burns more oil now, and the shop shows the tank in seconds of light instead of a raw number.
Moving to another lighthouse costs money now, and each posting you complete gives a permanent +25 % coins and +1 boat per wave, so it's a real goal instead of a wait.
Two new upgrades: Marked Channel (more boats per wave, up to 8) and Lighthouse Renown (big ships pick you more often).
Islet decorations now each give a small bonus, written in their description.
Fixed the wonky hitbox when a boat passes close to the lighthouse. @AnotherDuck
Easter eggs beyond the whale and selectable missions are next. Keep it coming, this was genuinely the most useful feedback I could have got.