The most frequently asked question about The Last Guardian is whether it's worth all those years of waiting. Well, in short, of course not. The Last Guardian is not the greatest game of all time, nor is it a masterpiece capable of breaking barriers. If this was the kind of unrealistic expectation you had for The Last Guardian, then you're in for a massive letdown. On the other hand, there are those that predicted a disaster, a game that would never be able to come together. That assumption is also wrong. Instead, The Last Guardian is "merely" a good game, a special experience that deserves to be played, despite several flaws.
This PS4 exclusive was developed by Team Ico and created by the mind of the great Fumito Ueda - in short, the same people that gave us Ico and Shadow of the Colossus, and this heritage is evident throughout the game. In fact, The Last Guardian seems to be almost embedded in a concept between those two games. Like Ico, you will be exploring a huge medieval-inspired structure, tweaked with some bizarre technology, all the while working your way through platforms and puzzles while in control of a young man. The big difference compared to Ico is that, instead of a fragile girl, this time you will be accompanied by Trico, a huge creature that could have been one of the colossi of Shadow of the Colossus.
Trico is the star of The Last Guardian, and possibly the biggest reason for the game's successive delays. This is easily the most vivid creature we've seen in a game, to the point of it almost being scary. The brilliant AI behaviour is accompanied by innumerable details of great quality that help to develop the creature's credibility. Animations and ear-ticks, the way he plays with barrels and objects, how puzzled he sometimes looks at the boy, and the numerous sounds he produces in different contexts - they're all elements that combine to create this fantastic creature.
The credibility of Trico's animations and sounds is impressive, but it's his behaviour in the game that helps sell the illusion that we're dealing with a living creature. Games rarely have the courage to put AI controlled characters accompanying the player for long periods of time, and when they do, we usually see bizarre behaviour, such as when they get stuck on the scenery, or block the player's path. Now imagine that these characters were the size of a building and had to jump between numerous platforms, interact with objects, and go through small, narrow passages. The fact that Trico's behaviour is so believable, without causing some of the aforementioned problems, is possibly the biggest triumph of The Last Guardian and its creators.
The player can never directly control Trico, but may suggest certain things. The boy has four actions that he can perform - jump, push, crouch, and interact - all executed with the DualShock's face buttons. If you press R1 (alone it calls Trico) and one of the face buttons, you will suggest Trico to perform the same action, like jumping and interacting. There are puzzles that require these actions, and the game doesn't make it very clear that you can make these suggestions, so remember them.
Creating an artificially intelligent character with such credible behavior, following the player, facing opponents, and interacting with objects that are not always fixed, must have been one of the main factors in the delay. Maybe that's why we've never seen an AI character behave so realistically, and that's why it's unlikely that we're going to see anything similar anytime soon, because it's simply not worth the effort. As fantastic as Trico is, it has little impact on the quality of the game. If the gameplay is not interesting or varied, or if the design of the levels is not good, the actions of an AI-controlled character simply won't matter.