If the game freezes, just click inside it (games can get unresponsive if you click elsewhere on the page).
There are 8 levels in one world with 4 different power ups, including Mushroom Mario, Fire Mario, Liquid Mario, and Magic Mario. In addition, there are two vehicles in some levels, the Jackhammer and the Mario 'Copter.
Arrow keys to move.
X to jump.
Z for special.