What's refreshing about Outcast is that instead of following a linear storyline, you're free to collect Mon in any order you'd like. The entire planet of Adelpha can be explored once the tutorial ends, with distant lands just a portal jump away. You're can explore, fight enemy soldiers, or hunt for secluded items at your own pace, and Outcast will never tell you which method is the correct one. You'll still learn strategies through trial and error - running into enemy outposts with just a pistol is always a bad idea - but those mistakes are always yours to make.
The open world itself can be something of a mixed bag, mostly because it was something few games attempted on this scale. Adelpha is huge and varied, with each new environment looking impressive as you exit a portal. But many areas also lack depth, filled with large empty stretches that contain little of interest. You'll want to take advantage of fast-travel methods as quickly as possible, whether unlocking rideable alien creatures, or dropping teleport beacons at key locations.
One of my favorite elements from Outcast was how it handled NPCs. Each in-game character has their own function and purpose, outside of simply helping Slade with a particular mission. Quest-giving Talan can be found working in fields, while boss characters might have their our routines and patrols to follow. Sometimes you'll revisit where you met a particular NPC, only to find they've wandered off to handle their daily tasks. And if you do lose track of a character, you can usually ask a nearby Talan for directions to their current location. These are minor details, but they really help Adelpha feel like a immersive place instead of a digital world of enemies to shoot.
Another great touch is how Outcast takes common game mechanics and integrates them into the lore. The digital HUD emanating from your helmet is the most obvious example, even though it's fairly common in sci-fi games these days. Instead of a built-in aiming cursor on the screen, you'll rely on laser sights and aiming assists built into individual weapons. Slade's massive inventory storage is accounted for due to advanced technology in your backpack, meaning you can carry more objects than the Doom Marine without being burdened. Even saving the game is handled by an in-universe item - the "Gaamsaav", which preserves your essence to be restored at a later time. These are minor points, but they uniting the game world and mechanics really help Outcast feel immersive in a way few open world games can.
That's not to say all of Outcast's mechanics run smoothly: Its combat systems are especially clumsy in both first and third person views. The problem is everything from heavy weapons to your lowly pistol fires slow-moving projectiles, and most enemies know enough to dodge. This reduces every combat to a dance where you're avoiding incoming projectiles while trying to correctly time your own shots. Now consider that enemy numbers can rise to almost a dozen soldiers at once, and you'll probably want to avoid combat altogether until your Talan allies help you weaken them.
Yet for all the problems I've mentioned, there's something really special about Outcast. It truly feels like the first game of its kind: Awkwardly executed, but filled with a creative energy that's deeply appealing. It's no wonder developers took what Outcast accomplished and improved upon it, creating the open world systems we now take for granted. That's a creative drive more open world games could use, even if they stumble in the attempt like Outcast did.