Marathon 2 is mostly the same as Marathon 1, except for some small changes to gameplay and massively improved level design.
Levels are more varied, more interesting, and most importantly, more easily navigated compared to Marathon 1. The levels can be big, sprawling, and complex, but they're laid out in such a way that you can always tell where you are, even when rooms over rooms bunch together on the automap. Getting lost in Marathon 2 was very rare for me. Levels have much more variety in terms of how open the spaces can be, how they use verticality, and how they use different shapes and layouts to create unique and distinctive areas to explore and fight in. The obnoxious switch puzzles from Marathon 1 are completely absent here, so progress through the levels never feels like it grinds to a halt. In addition, swimming has been added as a mechanic, alongside pools of liquid to swim around in, and underwater sections to explore in certain levels. Swimming is actually surprisingly functional. It makes the oxygen meter that was technically in Marathon 1 way more relevant, and while it can feel somewhat janky, it still controls pretty decently for the most part. Better swimming controls would be demonstrated by Duke Nukem 3D about a month later, and by Quake about half a year later, but it's still very impressive that Bungie managed to make swimming in an FPS as good as it was in 1995.
Combat is mostly the same as it was in Marathon 1, save for some small changes. Enemies feel like they come in larger numbers more frequently. Combine that with the more wide, open spaces that Marathon 2's levels can sometimes have, and some of the encounters feel more fast-paced and frantic than they were before. You reload slightly faster, your energy pistol deals more damage against cybernetic enemies, higher tier enemies feel more commonplace, and you get one new weapon, which is a shotgun. It is also one of my favorite shotguns in gaming. It deals a ton of damage, it feels really punchy and satisfying to shoot, it reloads quickly after every shot so you can keep a nice rhythm going, it's lever-action and you reload it with a one-handed flip like in Terminator 2, and best of all, you can dual-wield them. You can go on some really wonderful rampages with these things, especially when the levels start to throw huge hordes of enemies your way. At the same time, their ammo supply tends to be fairly limited, so you can't use them so often that they completely destroy the balance. It's a power weapon, and the game very much balances it like a power weapon.
The visual and environmental design got a huge overhaul as well. As much as I liked the cartoony, graphic novel art style of Marathon 1, the more realistic and detailed art direction of Marathon 2 just feels so much more fitting for the setting and tone. The textures have more detail and more color, and there's more of an attempt to make certain areas feel like they serve an actual purpose. It goes a long way toward making the planet of Lh'owon feel more like a place, as opposed to the strange, abstract environments of Marathon 1. The artwork used for the intermission screens is especially gorgeous. As for the music, there is precisely one track in the entire game, and it's used for the main menu. For the actual game, rather than having a soundtrack, Bungie instead decided to use environmental noises and soundscapes to convey a sense of atmosphere. This is a pretty avant-garde choice to make for an FPS in 1995, but there are moments where it just falls apart. Sometimes it does actually work decently well: the sound of wind blowing, distant explosions from an orbital bombardment, splashing water, gurgling swamp sludge, bubbling lava; these sounds are pretty okay for the time when it comes to creating an atmosphere. Other times it kinda just sounds bad. An emergency alarm uses a stock air horn sound. A malfunctioning computer sounds like a buzzer on a game show. Platforms rising in and out of the water will loop and spam the same singular splashing noise over and over again. It does sound okay sometimes, but I still would have liked there to be a soundtrack. Some nice ambient music would have complimented the good soundscapes while covering up some of the jankier noises.
Overall, Marathon 2 is a pretty big improvement on Marathon 1. All the levels are really fun and solid, the combat is as fun as ever, the atmosphere is still great despite some rough spots, and the story is still excellent. Like with Marathon 1, though, I'm not going to get into the story since I think it's best experienced yourself. It's a great game, and it's also free! So after you're finished with Marathon 1, check this out too!
