More islands and more neighbors means more chances to get invaded from an angle you weren't watching. A faster, scrappier version of Large islands.
Open Play, then pick Medium islands from the map list before you start a match. Everything else — your country, difficulty, and game mode — works exactly the same as any other board.
Play nowEach match on this map generates a shareable seed, so if a game turns into a great story you can send the code to a friend and they'll start on the exact same board.