: Drop the .iso file into the psp folder.

The Nintendo DS utilizes dual screens and a touch interface. Recalbox uses the or MelonDS cores via RetroArch to handle this. Use these optimizations for a seamless arcade experience on your PC monitor: Screen Layout Settings

: This usually indicates missing or corrupt DS BIOS files. Double-check your share/bios folder.

Load the ROM. Increase the internal 3D rendering resolution (2x or 3x) to make the game's 3D background elements look incredibly crisp on a modern 1080p or 4K monitor. Option B: The "Metal Slug XX" PC Alternative

The game was originally developed by SNK Playmore exclusively for the Nintendo DS in 2008 [1]. It later received an upgraded console port called Metal Slug XX for the PlayStation Portable (PSP), Xbox 360, and PlayStation 4 [1].