Metal Slug - 1st Mission arrived in 1999 as one of the early action titles for SNK's Neo Geo Pocket Color, a handheld that had launched the same year and was positioning itself as a serious rival to Nintendo's Game Boy Color. Developed by Ukiyotei — a studio with experience adapting arcade properties to more constrained hardware — the game faced the considerable challenge of translating the kinetic, sprite-rich spectacle of SNK's beloved Metal Slug arcade series onto a small screen with a tiny two-button layout and a thumbstick-style micro-lever. The result was a surprisingly faithful distillation of the franchise's core identity rather than a mere name-licensed cash-in.
Gameplay is structured as a side-scrolling run-and-gun across multiple stages that echo the format of the arcade originals. The player controls a lone soldier who must fight through waves of enemy infantry, armored vehicles, and boss encounters using a standard shot and a grenade/bomb attack mapped to the two face buttons. The micro-lever on the Neo Geo Pocket Color, praised at the time for its satisfying tactile click, handles movement and aiming direction, and while the absence of a full d-pad means diagonal shooting requires some adjustment, the controls feel considered rather than compromised. Iconic Metal Slug vehicles — most notably the titular slug tank — appear and can be boarded, granting the player heavier firepower and an extra hit point buffer before being ejected on foot. Prisoners of war are scattered through levels and can be rescued for item drops, preserving one of the series' most recognizable gameplay loops. The stage structure is largely linear, with each level culminating in a boss fight that demands pattern recognition and careful resource management given the limited screen real estate.
Visually, Ukiyotei made smart use of the Neo Geo Pocket Color's hardware. Sprites are compact but expressive, retaining the chunky, cartoon-military aesthetic of the arcade games. Enemy soldiers react with exaggerated animations when hit, and the slug vehicles have recognizable silhouettes despite the reduced resolution. The soundtrack, while necessarily simpler than the arcade counterparts, delivers upbeat, march-inflected chiptune compositions that suit the action well.
In its era, the game was received as a competent and enjoyable portable action title that demonstrated the Neo Geo Pocket Color could host genuine genre experiences rather than only puzzle or fighting games. It appealed both to existing Metal Slug fans wanting a portable fix and to newcomers drawn to the handheld's library. The game's existence also underscored SNK's strategy of using the Neo Geo Pocket Color to extend its arcade brands into the handheld space, a strategy that also produced portable versions of King of Fighters and Samurai Shodown content. A follow-up, Metal Slug - 2nd Mission, was released for the same platform in 2000, expanding on the formula with additional stages and a second playable character, confirming that 1st Mission had established a viable template worth continuing.
