Parkourier

Step 1: steam://install/480/ | Use this link in the browser and install Spacewar on Steam (Tiny download)

Step 2: Add the Parkourier.exe as a Non Steam game

Step 3: To Play the game, one person presses the host button while everybody else waits in the menu. Then the person who is hosting, invites the people waiting in the menu to the game. 

These people accept the invite and get added to the waiting area where everybody has to ready up by pressing the R button in the game. 

Once everybody is readied up the host can press the start game button.