melonDS is a free open-source and highly customizable emulator. Its main features include:

• Light and dark themes
• Customizable controller layouts and backgrounds: create the best layout for each individual game with only what you really need
• Fast-forward support: skip cutscenes and tedious parts at high speed
• Save state support: save your progress at any point and return to it instantly
• Cheat code support: import cheats to help you advance in your adventures or unlock special features (no cheats are provided out of the box)
• Gamepad support: control the game using your wired or Bluetooth controllers

Notes:
• No ROM files are provided. You must extract ROM files from your own cartridges and/or systems
• Emulation requires the use of custom BIOS and firmware files extracted from a real system