Instructions
Play
Use your joystick (or control pad on consoles) to move left or right. Press up and down on the joystick when standing near a ladder to climb it. Press the sole button on the arcade cabinet, or a button on your console controller, to jump.
Avoid hazards such as barrels, fire, pies and springs. Be careful not to fall long distances, as Mario cannot stand it.
Move Mario to the top of the screen, where Pauline is waiting, in the first, second and third levels (or just the first two levels in the Nintendo Entertainment System version).
Defeat Donkey Kong by running or jumping over each floor connector, thus removing them, in the fourth level (or third level for original Nintendo).
Strategy
Use the hammer only as a last resort in the first and second levels. Because you can't climb ladders with them, you can't make significant progress, and when the hammer disappears you may actually be surrounded by enemies.
Pay close attention to where the springs land in the third level, and move Mario as close as you can. As soon as the spring flies past you, move on to the next safe area.
Destroy the floor connectors strategically in the fourth level--you can block off incoming fire enemies this way.
Complete each level as fast as possible to reap the highest bonus score.