Editor's Note: Because multiplayer servers were limited before launch, we're publishing thoughts in two parts. Today's portion of the review focuses solely on the single-player experience. The second part of the review will cover multiplayer and include the final score.

Last year's release of Halo: The Master Chief Collection brought nearly all of the mainline Halo games to the Xbox One (with the sole exception of Halo: Reach), but it didn't really bring us anything new. This week's release of Halo 5: Guardians is the first new campaign experience in three years, and it delivers the goods. The campaign in Halo 5 builds on some of the story framework laid down in Halo 4, but it more than exceeds what we experienced the last time we tagged along on one of Master Chief's adventures.

From a story perspective, Halo 5 is clearly the middle installment in a trilogy that started with Halo 4. Although Master Chief is still the main catalyst as far as story events are concerned, he's not the focus of the game. In fact, you're going to spend more than half of Halo 5 playing as Spartan Locke. From a gameplay perspective, it's not much different, but if you're attached to the idea of Master Chief, making the switch in a mainline Halo game may be just as jarring as the first time Metal Gear Solid 2 players realized they were going to be playing the majority of that game as Raiden rather than Solid Snake.

Halo 5's plot does take a few risks, but nothing comes as a total surprise. If you were paying attention in Halo 4, much of what develops was foreshadowed. Hardcore fans will appreciate some of the references to other events, but you don't need to be intimately familiar with any of the secondary lore (books, etc.) to keep up with Halo 5.

Fans of Halo 3: ODST will appreciate the return of Buck. Voiced by Nathan Fillion, Buck has been upgraded to full Spartan status for Halo 5. Although you don't get to play as him, he is part of the core fireteam and one of the stand-out characters. In fact, Fillion's portrayal of Buck easily eclipses Locke, making me wonder why he wasn't made the primary player character.

Because Halo 5 is designed for co-op play, you are always in the game with a full fireteam. As a solo player, this means you have three AI buddies at your disposal. For the most part, they perform well, taking out secondary targets and generally staying alive on Heroic difficulty. If an AI team member is killed, he eventually respawns after a minute or so. If you get knocked down, an AI team member can revive you so long as it is done quickly enough. If they take too long, or if all of your AI members are down, it's time to reload from the last checkpoint.

All in all, Halo 5 feels like it was tuned for Heroic difficulty, with the campaign taking about 8 to 12 hours to play through. Normal difficulty is more akin to easy than anything else, and Legendary provides a challenge for veteran players. Difficulty is consistent throughout the campaign, with the singular exception of one enemy, the Warden Eternal.

Halo 5's only real "boss" enemy, the Warden Eternal appears multiple times throughout the campaign. You'll have to fight him a handful of times, with the last two battles featuring multiple copies. The challenge presented by the Warden is the fact that he can only be damaged by hitting him from behind. This might sound simple enough, but it doesn't take into account the stupidity of the friendly AI.

I said earlier that the AI does a decent job of holding its own, and that is true against generic enemies. Against the Warden, though, the friendly AI completely falls apart.

The only commands you can give to your fireteam are attack and hold. If you don't give them any commands, they follow you. If you tell them to hold a position, they cluster and become easy prey for the Warden. Actual, living human players can run a game of distraction by separating out and firing on the Warden, while another runs around back for the kill. Getting the AI to do the same is an exercise in luck. You can't issue individual orders, and the chances of them landing kill shots while you distract the Warden is slim. As a result, fighting the Warden is either a simple affair or incredibly frustrating, depending on how quickly you get a clean shot.

Outside of the Warden fights, the only other place the friendly AI falls apart is when driving. Yes, Halo vehicles have never been high performers when it comes to controls, but holy crap, the AI is bad at driving. Just don't even bother. Either take the wheel yourself or go on foot.

Enemy AI, on the other hand, manages to work together quite well. Low-level enemies gather to draw fire, while a sniper attempts to take you out from afar. I also noticed that the enemy AI won't hesitate to flank if you stay in one spot for too long. Staying alive means continual movement.

Level design is a noticeable step up from Halo 4, with large, expansive areas and plenty of little nooks and crannies to explore. There is some minor backtracking for story reasons, but the majority of the adventure always feels new. You don't get the sense that level sections are simply being repeated to extend play time. Some sections require you to completely clear out all enemies before moving on, while others allow for minimal combat if you know the optimal path through the area. Discovering those paths will be a necessity for the speed runners out there.

Visually, Halo 5 is strong, even if it doesn't always hit a full 1080p. Instead of resolution, 343 opted for a 60 fps display throughout the game, and the trade-off is well worth it. Environments still look good, and the controls are smooth and responsive. That latter bit is very important when in the middle of a firefight. The visual quality carries over to the cinema scenes, which almost look as though they're from a Halo animated film. There are more than a few scenes that could make for a great desktop background.

The music and sound effects are also worth calling out. Halo 5's score reuses some key motifs from the franchise, but the majority of it is new. In the middle of a battle, you might not be consciously thinking of the background music, but what's here always fits the moment quite well. Positional sound effects are also well used, with audio cues being an easy way to identify the location of enemies.

If Halo 5's campaign didn't rely so heavily on the Warden Eternal, it would have been a smoother experience. That creature is the one place where it feels like 343 got a little lazy in the design and simply cut and pasted him multiple times rather than creating additional boss creatures.

You'll need to check back in a few days for our multiplayer verdict and final score, but rest assured, if the campaign is your primary point of interest, you can't go wrong with Halo 5. It's not the best mainline Halo campaign out there, but it is a better experience than Halo 4's campaign.

Score: TBD