Metroid II: Return of Samus is an action-adventure game developed and published by Nintendo for the Game Boy. You can save your data to your browser. Click the settings icon and press "Save State Location", then change it to "Keep in Browser". You can enter fullscreen by hovering over the game and pressing the fullscreen button in the bottom right If pressing enter causes the game to tab in and out, just click on the middle of the game to refocus.