In Reworld, players attempt to terraform a newly discovered planet, and to do that they need to use terrabots to establish new cities and shuttles to deliver materials that will populate those locations.
In game terms, over five rounds players fill the five levels of their spaceship with tiles featuring terrabots, shuttles, material vessels, and satellites. Each round twenty of these tiles are placed at random around the perimeter of a large ship, and each player receives a hand of cards. On a turn, a player can play one or more cards to claim a tile following these rules:
Once everyone has no cards in hand or cannot play further, the round ends. Any remaining tiles are thrown away, then you reset the board and deal out a new hand of cards. After five rounds, players now deploy these tiles onto the new planet, each turn playing 1-3 of the leftmost tiles from the row of their choice to create their personal terraformed world. If you deploy a terrabot, which are labeled A-E, you start a new city with this letter or extend an existing city of yours. Material vessels, which come in five colors, can be delivered to the planet's surface only if attached to shuttles, and each city can have vessels of only a single color. Satellites provide bonus scoring when added to a city. Shuttles and satellites can also be used for shields to protect your newborn planet.
Players earn points during the first half of the game for picking up terrabots and having cards left in hand. During the second half, players score for deploying satellites and for meeting targets set at the start of the game, e.g. having a city with eight tiles in it, having a city of each letter, emptying a level on your spaceship, having a certain number of shields, etc.
Once all the spaceships are empty, players score their final points for how well they've developed each city and their shields in comparison with their fellow terraformers. Whoever scores the most points wins.