The Chaos Engine is in my opinion the magnus opus of the Bitmap Brothers, that showcased the most refined version of their highly recognizable art direction combined with almost perfect playability. It’s a top-down action shooter where you have to traverse four worlds with each four levels to final confront and if possible defeat the eponymous Chaos Engine.
The first few levels start easy but get noticeable harder in each successive level: new enemies that move faster and more erratic or can even climb walls, that can fire more deadly projectiles and can take on more damage than before. The only advantage you have is to collect as much money as possible in each level, to buy upgrades and keep pace with the arms race.
What adds to the immense replayability of the game is that every level has countless secrets that allow you to collect even more money, often offering two or three different paths through each level and various exits. I don’t remember any other game of this type that had such an amount of content and variety, at least if we’re talking about top-down shooters. You’ll always wonder what the best way to collect to most amount of money each level is and whether you’ll find a new secret on your next run.
You’re also not alone, a second soldier is always following you, though this is also one of my biggest gripe with the game. The second soldier is more obstruction than useful tool and how the game shoves him into your face gets annoying very fast. The second soldier also acts incredibly stupid most of the time (Dos-version). You can increase his intelligence, but by the point you have enough money to do so, you rather wish you could kill him forever. Sadly the game forces you to resurrect him repeatedly.
Overall it’s pretty hard. Coins appear after you hit an enemy, but shortly afterwards disappear again. You need them to power up, or you’re soon hopelessly outclassed, but if you’re too fast to collect them, you might bump into another enemy who comes from the same spawn point as the first one.
Shooting is only 8-directional and you can’t move while you’re shooting, while your enemies don’t seem limited by this as much as you. Your hitbox is quite large while enemies have a seemingly smaller one and often you miss them by a single pixel. The later levels are quite trying, and the final boss is extremely difficult due to how the controls limit you. Also later on you often can’t outrun enemies and if you don’t start hitting them once they appear, you already lost valuable hit points.
The game was released on a buttload of systems: Amiga and later Amiga CD32, Atari ST, on floppy disk on MS-Dos and later in an enchanced CD-version (which despite a patch for stuck keys remains almost unplayable, as the patch doesn’t really alleviate the problem), and on the Genesis and the SNES.
The floppy disk version for MS-Dos is quite good (but has weak sound). The SNES (screens above) version looks a bit more colorful, has actually a soundtrack and is much faster, including much faster enemy spawning, which makes coin farming from spawning enemies more difficult and the whole game even more nail-biting hard.
The Genesis version has more muted colors, but has a similar tempo as the Dos-version and is in general better balanced for playability, and just as the SNES-version has sound as well. Both the SNES and the Genesis show also much better AI for your companion.
The one major drawback of the Genesis version is that you can’t exchange abilities with your partner, which makes the early game easier if you take the Scientist and use his medkit in the Dos- and SNES-version.
The European version of the Genesis Chaos Engine (both Genesis and SNES US-versions are called Soldiers of Fortune) has three selectable difficulties, which is not in the US-version and neither in any other.