Ok so, after reflexions I have choisen an idea. Player will control a spaceship that can explore space, ocean and planets. I have a base of code in Lua and Love2D. Next step : search graphics into the deep of Internet :-)

For create fun, I'm going to create a lot of constraints and a goal to reach.

Perhaps this will help me =-) https://deep-fold.itch.io/pixel-planet-generator