Marathon Infinity is the hardest game in the series, and the most cryptic in terms of its story. It's also my favorite in the series.
The story is still excellent, but this is Marathon at its most cryptic, disjointed, and postmodern when it comes to its presentation. Some things you'll have to pay very close attention to in order to understand what's going on, other things are really metaphorical and need to be interpreted based on what you know about the events, characters, and world in the previous two games. I personally love weird, complex stories like this, especially when there's enough depth to make putting all the pieces together feel meaningful, and Infinity absolutely fits that description. There's a ton of depth, detail, and meaning to be found in Marathon Infinity's story, even if it might just look like madness on the surface. I'm not going to get into any of the details of the story, but if you ever get lost, I can highly recommend MandaloreGaming's videos on Marathon since he does an excellent job at explaining the story in broad strokes.
As for the gameplay, it's basically more Marathon 2, but with some new things added. You get a new weapon, which is a flechette SMG. It's powerful and accurate, but chews through ammo pretty fast, and ammo for it is pretty scarce on top of that. It's a neat addition to the weapon roster, even if I forgot it existed most of the time. There are also new levels where you fight against human enemies, which consist of hostile versions of the human soldiers from Marathon 2, and a new armored human enemy that uses an energy pistol. They're both pretty accurate at long range, they both hit hard, and they both have smaller sprites relative to the non-human enemies, making them a bit trickier to hit at a distance. At the same time, they don't have much health, and they're tracked on your automap like any other human NPC from the previous games, so it's possible to get the drop on them before they snipe you. They're actually pretty fun to fight and make up some of the more tense encounters in the game. In general, Infinity is also a much harder game compared to 2. Levels are bigger and more complex to the point where it is possible to get lost if you're not paying attention to your surroundings. The enemy count in each level feels higher, while your overall supply of ammo is slightly more constrained than before. It really pushes you to use all your weapons effectively, and to explore around more for secret ammo caches. Levels can have more devious layouts, with more opportunities for ambushes, fights in close quarters, and more awkward or limited cover to make some fights feel more tense and hectic. Environmental hazards are more plentiful, and oxygen stations are more difficult to come by, putting more pressure on you to navigate underwater sections and hard vacuum levels more quickly. At the same time, none of Infinity's levels ever felt unfair or unfun to play. Infinity has some extremely well-crafted difficulty that can feel very tense and even stressful, but never antagonistic toward the player. Even the worst level in the game is nowhere near the low points that Marathon 1 had.
As for the environments, while Marathon 2 did a pretty alright job at making the levels feel like actual places, Infinity feels like it does this even better. There are more recognizable buildings and structures, more areas that feel like they serve a purpose, and some really nice use of level geometry to make more intricate details in the walls, floors, and ceilings of some levels. The level of detail in the textures feels on par with Marathon 2, but Infinity's art style feels much more dark and moody compared to 2. The color palette is more muted and desaturated, low-light areas are more common, and some areas feel like they return to that metallic, industrial feel that Marathon 1 had. The art direction fits the darker, more cosmic horror-oriented tone of Infinity really well. Infinity handles music the exact same way as 2, in that the only actual track in the game is used for the main menu, and everything else is just environmental soundscapes. However, it feels like Infinity has really cut down on the number of janky environmental sounds it uses, and has added some really nice ones on top of that. It feels like a noticeable improvement over 2, even though I still think Infinity would have benefited from a proper ambient music soundtrack.
Infinity is a fantastic conclusion to one of my favorite series of FPS games, and it's also my favorite game in this series. I already thought Marathon 2 was really fun, and Infinity feels like a slight step up from that while also offering an increased baseline level of difficulty that I found really engaging. Infinity continues Marathon's already excellent story, while also bringing all the weird postmodern stuff that I love directly to the forefront. On top of that, it has some excellent environments and atmosphere that never felt like it had any of the more noticeable shortcomings that popped up occasionally in the earlier games. This game is excellent, and it's also free! So definitely check this out once you play through the first two games
