Friday is a solo adventure - only you can win the game!
You are helping Robinson, who came ashore on your island, fight against many hazards. At the beginning, Robinson is not very skillful. With each fight he wins you will improve his abilities, but defeats are also helping to get rid of his worst habits. However, life on the island is energy-sapping, so that Robinson not only gains experiences during his time, there, but also starts aging and tends to get clumsy.
Friday is a deck-building game in which you try to add good cards to the deck and get rid of the bad ones. With this deck you fight against the dangers. If you defeat one danger (card), you will add this card to your deck (good). If you lose against a danger, you lose some health tokens, but you can get rid of the cards you lost with (generally weaker cards).
The game ends when Robinson loses all his health points, or (preferrably!) defeats 2 tough pirates!