Use the arrow keys or the WASD keys to move around, use the X key to shoot fireballs if you are fire Mario and to enter the pipe press the down key or the S key. Use the 0 key to enter the level editor, to switch tiles use the number 1 2 3 4 5 6 and 9 keys, to place the tiles do a click, to select the tile under the mouse cursor press the E key, to turn the auto arranging on and off press the Q key and if the auto arranging is on and you want to add a pipe right next to another one or add a blue or an orange platform on top of another platform press the space key and hold the mouse down. If you want Mario to enter the pipe press the number 6 until you find two arrows, one which is facing up and the other one down. The arrow that is facing down is for Mario going inside the pipe and add this at the top left of the pipe and the arrow that is facing up is for Mario going out of the pipe and add this at the top right of the pipe after you add the arrow that is facing down. If you want to stop the enemies walking off the platform press the number 6 key until you find the X and add this at the edge of the platform. Also if you want to switch level press the L key and to reset a level press the R key.
Thank you griffpatch about the tutorial of how to make a tile scrolling game.