Sleep Mode

Sleep Mode is a standby feature that allows the system to reserve battery power without turning it off or losing the game's progress. This function is useful for players who wanted to take a break in the middle of the playing session for a short while.

The Sleep Mode option is present in certain Game Boy Advance titles, and every Metroid game for the system has it. In Metroid Fusion and Metroid: Zero Mission (named Easy Sleep in the latter title), pressing on the map screen brings up the Sleep Mode screen. In the Classic NES Series port of Metroid, the Sleep Mode option can be selected from the Menu screen. Activating Sleep Mode turns off the screen and sound while still retaining the game's progress. Simultaneously pressing the, and  buttons resumes the game from Sleep Mode. The Sleep Mode option can also be done with the Nintendo 3DS Virtual Console versions of GBA titles from the Ambassador Program but not the Wii U Virtual Console releases.

On most games for the Nintendo DS and later the Nintendo 3DS, closing the system activates Sleep Mode and opening it resumes the game. This feature is non-functional for some Nintendo DS games, such as Metroid Prime Hunters: First Hunt, where the game is still running and does not reserve battery power when the system is closed.

Profiles

 * Metroid Fusion instruction booklet (page 25): "From this screen, you can access Sleep Mode. This mode allows you to conserve battery life without turning the game off. The Sleep Mode function is convenient when you want to take a short break, but aren't near a Save Station."
 * Metroid: Zero Mission instruction booklet (page 20): "Easy Sleep allows you to conserve battery life without turning the power OFF. Easy Sleep is useful for when you want to take a short break but aren't near a Save Room."
 * Classic NES Series: Metroid instruction booklet (page 10): "The power remains ON, but the liquid crystal display will turn off and the game will pause to reduce battery consumption."
 * Metroid Prime Hunters instruction booklet (page 8): "If you close your Nintendo DS during a game, it will go into Sleep Mode to save battery life. Open the DS again to resume the game."