Arrow Keys: For all three versions you must use the Left and Right Arrow Keys to make your currently-selected Tiny run left and right; you must also use the Up Arrow Key to make him jump (with each jump, he gains momentum, and will reach his maximum height after three of them, but he cannot jump unless he's on the ground at the start of one). To switch to one of the other available Tinies on the current level you must push the Down Arrow Key when your current one's on the ground to make him dematerialise - and you can then pick which of the other available Tinies you want to switch to by pushing the Left and Right Arrow Keys (ones that are not available on the current level are black) then press the Up Arrow Key to confirm your choice and make the new Tiny rematerialise where the previous one stood. You'll have to make use of all four Tinies' powers to complete the game.
Space: In the original MS-DOS version, you have to use the spacebar to make your currently-selected Tiny use his power; however, in the Amiga and CD32 versions this is done by pressing Shift instead. The yellow Tiny, who can pass through flames, can shoot fireballs at the enemies - and the longer you hold down the key the more powerful they'll be. The blue Tiny, however, can dive under water if you press the Down Arrow Key while he's in it; he can also spit air bubbles at enemies (and make water levels rise in narrow spaces). The green Tiny can throw a grappling hook to latch onto any object or part of the level on which he can run, as well as the majority of flying enemies - and pushing the key while his line is in the air will latch it onto an object if it is less than half a screen away from him, while pressing it in conjunction with any of the Arrow Keys will hook it diagonally (doing this when his line is hooked shall also lengthen or shorten it, and the Tiny can also pull some objects towards him by latching onto them with his line then walking away from them). Lastly, the red Tiny can eat certain parts of the levels; pressing the key alone shall cause him to eat parts of them underneath him, while pressing it in conjunction with the Left or Right Arrow Keys will cause him to eat parts to his left or right. The Tinies will lose a life between them if any of them touch a sharp object, fall into an acid pit, or run out of time, and if the blue, green or red ones touch a flame.
D-Pad: In both the SNES and Game Boy reskins, you must push the D-Pad left and right to make "Pac-Boy", as he is known for this game, run left and right; pushing it up and down while his grappling hook is latched onto an object or part of the level shall also either lengthen or shorten his line. The default assignments of the buttons in the SNES reskin are for "Action", for "Jump", and for "Change", and for "View" but they can be changed on the options screen (along with the game's speed, and it is also possible to toggle the music and effects on and off) - but in the Game Boy reskin, always makes "Pac-Boy" jump, while always makes him use his currently-selected power (holding it down while the fireball power is selected will also increase their strength, and you can also use to cycle through his available powers for the current level).