Mario's controls are all shown in-game from the title screen, but there's a few other controls I have to list here ◦ Up arrow to go in doors ◦ Z key to hold shells or springs ◦ P key to pause in a level or the world map ✦✦✦✦✦✦ To beat Bowser, avoid his attacks until he leaps high into the air; when he charges back down, he'll flip himself over and you can jump on his belly. Do this 3 times to defeat him.
