carterprince/justgba

JustGBA is an emulator for Android phones, meaning software that lets your phone pretend to be a different device so it can run programs made for that device. In this case, the device being imitated is the Game Boy Advance, Nintendo's handheld console from the early 2000s, so this app lets you play Game Boy Advance games directly on an Android phone. It is built on top of an existing project called gpSP, a well known Game Boy Advance emulator, and specifically targets modern Android phones with arm64 processors, which covers the vast majority of phones sold in recent years. The project's stated goal is to stay efficient, fast, and minimal rather than trying to add every possible feature. It relies on gpSP's just-in-time compiler, a technique that translates game code into instructions the phone's processor understands as the game runs, which the author says allows for very fast performance and low battery use, even when speeding through gameplay with fast forward. Among its features are several fast forward speeds, ranging from a mild 1.25 times up to a full 8 times or an unrestricted maximum speed, along with a toggle so you can turn fast forward on or off, or hold a button to speed up temporarily. It automatically restores your saved progress when you reopen a game, and lets you export or import your Game Boy Advance save files so they can be backed up or moved between devices. The app also supports both portrait and landscape orientations, keeps a list of recently played games on its main menu, and can display an on-screen frames-per-second counter. The author lists a couple of planned improvements still to come, including letting players remap which physical buttons control which in-game actions, and confirming that external game controllers work properly. Building the app yourself requires the Android SDK and a specific version of the Android NDK. The project is fully free and open source software, released under the GPL version 2 license, which it inherits from the gpSP project it is built on.