Twenty solution cards are dealt evenly among the players. Four problem cards are placed on the board to start the game, and a new one is added at the beginning of every player's turn.
On his turn, a player rolls a die to earn money, draws a solution card, and then resolves one or more problem cards by (i) discarding one or more solution cards that are the same color as the problem card(s) and whose sum of numbers equals or exceeds the sum of the numbers on the problem card(s); and (ii) paying the cost shown on the problem card(s). The resolved problem card(s) are worth victory points to the player.
After every round of turns, advance the Global Warming Index a distance equal to the values on the unresolved problem cards. Play until one player wins by reaching a certain number of victory points based on player count. Everyone loses if, before that happens, the Global Warming Index reaches 75.