Title Screen with planets : New game, load, credits, options, etc.
Start with a list of planets. Only Earth is unlocked. Mercury, Venus, Earth. You can hover the planet, but you can't select them, only Earth is accessible. Maybe some planets have ??? on them to show they are unlocked later. We can see the solar system and planets moving.
Progression
Earth -> Find Rocket in dungeon chest. Unlock Moon.
Moon -> Lunar boss, find special boots for Mercury.
Mercury -> Venus armor, in a chest after the final boss.
Earth
Earth dungeon found in a crater.
Mercury
Landscape: brown, craters
Monsters: Mercury zombie (hot/cold)
Day/night cycle
Hot Zombie (pale brown)
Cold Zombie (dark brown)
Music: Sound of mercury (youtube)
Mercury slimes
Drop cold bow/arrow
Drop hot bow/arrow
Chest: Can't open during the day, too hot (on fire)
Wait for night to open them
Or use special gloves.
Fuel
Require fuel to start rocket. Found in dungeon chests (all planets).
Need 25 fuel to start. Max 100 fuel. (Where is stored?)
Fuel required depends on distance between planets.
Progression
Earth
Mercury
Fuel