Metal Slug’s greatest asset, its sumptuously animated take on warfare, works for and against the play experience. The games merit an infinite credit ‘free play’ run purely on the grounds of aesthetic feast. Each mission bursts to life with the hand-drawn exploits of befuddled military men, overly elaborate death animations, and richly coloured plumes of explosion. The juicy interactions provide a certain degree of sensory satisfaction and Metal Slug pushes the shooting and stabbing out at a high frequency.

However, the chaotic gunfights also generate visual clutter. Although Metal Slug adheres to some key principles of good 2D shooter design (i.e. brightly coloured bullets set against muted backdrops), the eruption of animation can obscure the play space when untamed, resulting in stray bullets finding their way through the noise to the player target. Fan-favourite Metal Slug 3 is perhaps the series’ worst offender in this regard.

Another consequence of the aesthetic feast is the limits placed on the player’s movement options. The first couple of missions in each game simplify the challenges by setting soldiers along a horizontal—sometimes hilly—plane. Sure, they can jump or perhaps swing in from a vine, but from a spatial perspective the gameplay challenges remain simple. As the missions roll on, the landforms emphasise both axes of 2D space; jumping challenges broaden the game’s palette beyond shooting and stabbing; and enemies begin to attack from both directions.

Metal Slug 1, 2, and X somewhat attempt to ease the player into this increased complexity. Their gameplay challenges are more tailored around distinct gameplay ideas, allowing the developers to organise them appropriately. The later games are much less consistent. Still, even considering the more grounded approach of the earlier games, the lack of space to move characterises the stricter second halves of the games. All too often, the on-screen action locks the player into a state of inevitable death.

This unfairness extends to other aspects of the games. Some challenges cannot be beaten with the default handgun (such as the train carriages in the fifth mission of MSX). Enemies can enter the screen and attack with limited warning, and similarly some boss attacks don’t telegraph—or have very short—windup. These problems chip away at the integrity of the gameplay challenges. As such, it can be hard to take the series seriously. Fortunately, Metal Slug Anthology offers the option to play each game with unlimited credits in ‘free play’ mode, an ideal way to survey the sumptuous sights of Metal Slug’s unique brand of disorganised warfare.