You'll want to invest some time in your driving skills, too, because the AI competition has done its homework. Whereas Forza 4 suffered from an issue where opposing drivers would frequently overshoot sharp corners almost at random, there are very few of those mistakes in Horizon. The Forza AI's occasional aggressive streak remains intact--which you can have fun exploiting on the highway by luring anyone drafting you into oncoming traffic--but overall, the competition's intelligence feels somewhat improved.
Car customization is one area where Forza veterans may find themselves disappointed. You can still combine your own vinyl decals with new paint to create custom liveries, as well as upgrade your stock parts to become more competitive at higher racing tiers. But these systems are virtually identical to those found in the last few outings, and beyond that, Forza 4's advanced tuning system (where you could tweak tire pressure or brake bias, for instance) is a complete no-show in Horizon. On the plus side, the process of photographing your car and sharing your artwork is far more rewarding here than it has ever been thanks to the natural beauty and varied lighting of Horizon's virtual Colorado.
Those who invest time in designing their own vinyls and liveries will be happy to hear that the online storefront makes its return in Horizon (where you can import and sell your old vinyls), as do the vehicle-sharing car clubs introduced in Forza 4. Of course, Horizon's online offerings also extend to competitive multiplayer, where you can easily jump into a match using an intuitive and relatively effortless matchmaking lobby system.
At its best, Horizon's multiplayer is either incredibly intense (like gunning toward the finish line at night in a 20-mile point-to-point race) or ridiculously goofy (like eight cars careening around a golf course all trying to smash into one driver in the king-of-the-hill mode), but it's terrific fun throughout. And in a very nice touch, there's a slot machine system that rewards you with a random car or pile of credits every time you level up in multiplayer (which happens fast and often in the early goings).
While Horizon's competitive multiplayer is entertaining, its cooperative free-roam system feels like a missed opportunity. This is where you can get a bunch of players together in the same world and either wander around on your own or band together to complete co-op challenges such as combining for 100 near misses or having four players pass through the same speed trap at 200mph within five seconds of each other. Some of these challenges can be wonderfully entertaining, but the way they're communicated to players is clunky and obtuse. Only the host can select a challenge, and by default the game fails to tell you where a specific speed trap is located on the map. On top of that, you constantly have to pull up and scroll through a lengthy menu to remind yourself of the details of each challenge, sending your car coasting down the road without a driver to steer it.
It's a shame that outside of rivals mode challenges, which let you race your friends' ghosts after each festival event, single-player and multiplayer are kept at arm's length in Horizon. You have to exit out of the former to get to the latter, because there's no way for a friend to simply drop into your world for some free-roaming fun while you're taking part in festival events. With some tighter integration between single-player and multiplayer, and the sorts of customization opportunities found in car modification (there's no way to create your own race by selecting waypoints on the map, for instance), the free-roaming could have been an absolute blast. As it stands, though, it's fun for a little while, but that novelty wears out quickly.
Horizon may not be as socially capable as some open-world games, but it's still a terrific racer. It's hard to overstate just how beautiful the world is that Playground Games has created. From the foothills of the Rockies to the winding roads that scale desert cliffs, it's an absolute delight to put your car through its paces as you explore every last inch of asphalt. Horizon's occasional missteps may clash with the machinelike precision of the Motorsport games that preceded it, but its ambition and untethered road map more than make up for those faults. This is a game that understands the thrill of the open road, and in delivering that thrill it's an unqualified success.