What Retrocycles is
Retrocycles is a fast, unforgiving arena racer based on Armagetron Advanced, the long-running open source game. You ride a vehicle that never stops moving and leaves a deadly trail behind it. In the basic mode you can only turn at right angles, and you are locked in an arena with everyone else. The last one still alive wins. The whole game comes down to reading the space around you, cutting off routes, and not running into a wall or a trail.
Playing together
The focus is online play. Browse the server list, pick one that looks good, and stay on it as long as you like with the same people. Servers can hold at least 16 players, and some provide more slots. Four game modes are built in: Last Man Standing, Last Team Standing, Fortress and Sumo. In Fortress, two teams each own a zone they have to defend while trying to take the enemy's. In Sumo, everyone has to stay inside a circle that keeps shrinking.
Beyond those, modded servers add Racing, Capture the Flag and Mazes, plus one server with Rogue-ish RPG elements. If you prefer the couch, there is splitscreen for up to four players, and Remote Play Together is supported. Offline you can play against bots.
Before you start
Servers can change almost anything: speed, map size, trail length, timeouts, and even the strict right angle turn rule. Custom maps are supported, though there is no map editor. Expect the rules to feel different from server to server, so read what a server is running before you settle in. You can also customize your keyboard layout, which matters when quick, precise turns are the whole game.