Sleep Mode
Sleep Mode (Japanese: スリープ[1], or スリープモード) is a feature for the Nintendo DS and Nintendo 3DS families, and a feature for some Game Boy Advance titles such as Super Mario Advance 4: Super Mario Bros. 3. It allows the system to pause gameplay and save energy.
On a Nintendo DS and Nintendo 3DS, Sleep Mode can be accessed from both a system firmware menu and a supported title (some Game Boy Advance titles do not support Sleep Mode).
When Nintendo system or software is put into Sleep Mode, gameplay is temporarily halted until it is taken back out of Sleep Mode.
Sleep Mode, like other Nintendo DS titles (excluding Game Boy Advance titles from the Nintendo 3DS Ambassador Program) can be activated in Densetsu no Starfy 4' and The Legendary Starfy by closing the Nintendo DS system.
Sound effects
Some Nintendo DS titles play sound effects for closing and entering Sleep Mode. There are no sound effects for putting Densetsu no Starfy 4 in or out of Sleep Mode. When The Legendary Starfy is put into Sleep Mode, Starfy will cry "whee!" with a sad tone of voice. When The Legendary Starfy, is taken out of Sleep Mode, Starfy will say "fee" with a possibly surprised tone of voice.
Abuse
See List of glitches in the Nintendo DS games#Sleep Mode bug for further information.
Nintendo DS games can be unconventionally put into Sleep Mode using magnets. On a Nintendo DS or Nintendo DS Lite, but not with a Nintendo 3DS or Nintendo 3DS XL, there is a hardware glitch where quickly ejecting and reinserting a supported game in Sleep Mode will cause the Nintendo DS software to run incorrectly. The game may freeze when it tries to do specific actions, for example, a Densetsu no Starfy 4 affected by the glitch typically freezes after entering a door.
