Sonic Adventure is a free online game on shtoss.com. You can play Sonic Adventure in your browser absolutely free. Sonic teleported into Mario world by accident. The Mario World is divided into three different worlds where there are three kinds of monster living there. The three monsters are the flying turtle, the walking Goomba and the hard shell monster. They are waiting there to attack anyone who falls into there territory. Help Sonic explore the Mario world and cross the land to find an exit.