You wake up in a dark cave, covered in mysterious tattoos. A few feet away, in the gloom, you can make out the shape of a wounded giant. Part dog, part bird, the creature Trico is an extraordinary feat of animation, AI and creature design, and an astonishing companion for this 12-hour adventure. It's a testy relationship to begin with, however. Trico snarls and snaps as you pull spears out of his hide, feed him a few tasty glowing blue barrels, and release him from his chains.

The Last Guardian is a co-operative third-person puzzle platformer. Working together, you and Trico must escape the dark and climb the vast, crumbling edifices of the city in the valley. The city's pale towers are linked by half-shattered bridges. Haunted suits of armour guard the city's huge torchlit atriums. The place is full of strange statues, and covered in alien iconography. The whole area is bathed in a beautiful white sunlight. As with all of Fumito Ueda's games, The Last Guardian has the quality of an ancient fable, albeit one with a lot of switch puzzles.

Most of the puzzles rely on the size disparity between the boy and Trico. You can clamber through small gaps to pull switches, the creature can reach high areas and savagely swat any animated soldiers that might chase you. You can grab onto Trico's feathers and crawl all over him, which is a useful way to reach high ledges. Sometimes you leave the beast behind for a short time, to jump, climb and shimmy your way to a switch that opens a gate and lets the monster through. Trico's mournful howls will chase you through the corridors whenever you leave his sight.

The puzzles are simple, and exist largely to facilitate the relationship between boy and beast. Once you've demonstrated that you can find the glowing blue barrels that he enjoys as food, Trico is happy to follow you around, but soon he learns to interpret gestures you make by holding R1 and indicating directions and actions. You might point at a collapsed wall high above and press R1-triangle to mimic jumping, for example, and Trico will look up and judge for himself whether he can make the leap.

This is a collaborative process. Trico possesses a degree of autonomy and animal intelligence that allows him to act independently of your commands. He will sniff and paw at objects that might be useful, and in some areas it's best to simply hold onto his back as he vaults magnificently between distant platforms. This is not a story of a human and his pet, it's a symbiotic partnership that invites you to respect the monster, and to earn its respect in return.

Described plainly, in terms of switches and jumping puzzles, The Last Guardian doesn't sound like much, but it's a huge pleasure to spend time with Trico, who is realised with extraordinary subtlety and attention to detail. His eyes glow different colours to reflect different emotional states - yellow for hunger, purple for aggression - but his subtle changes in posture and expression tell you everything. If you've ever spent time with a dog you will see canine behaviour emerge in the form of sudden sneezes that seem to surprise the animal, and the attentive sitting posture of a creature keenly trying to understand what a human is telling them. If Trico can't squeeze through an archway, he will stick his head through, which delivers you the excellent sight of an enormous dog's face popping out of the wall, and gives you opportunity to stroke his nose with the circle button. Petting Trico calms him after fights, but it's also worth doing just to watch him nuzzle and yawn.

Trico has impressive command of his surroundings. The Last Guardian obsessively resists canned animations in favour of detailed environmental simulation, and this helps to embody the creature and give it the appearance of life beyond any ordinary AI companion. The barrels that Trico eats are physics objects that bobble around the scenery, but Trico is able to judge distance, paw at them, and snap them up. If you throw a barrel in front of him he can snap it out of the air. Unless he's not ready for it, of course. In that case it bounces off his face and he whimpers in surprise. After one such failed throw, the barrel rolled off into a vast pit. Trico gazed after it sadly and moaned.

The Last Guardian also does an extraordinary job of capturing Trico's size, weight and power. It is awe-inspiring to watch him spring hundreds of feet between narrow spires, and I mean that in the true sense of the word awe: this animal evokes a powerful combination of fear, wonder and respect. I even felt a swelling sense of pride as Trico overcame horrible circumstances and pushed himself to greater feats. He is a transcendent piece of design - the value of the evolving relationship with the creature far exceeds the simplistic trappings of a puzzle platformer, and makes up for the game's pronounced technical issues.

The Playstation 4 can barely handle The Last Guardian in some sections. Outdoors the framerate frequently dips, and in some sections absolutely tanks trying to render vast amounts of crumbling architecture. The controls - already weighty and imprecise - feel terribly sluggish in these sections. The boy you control is an unwieldy avatar, bumbling in a charming sort of way, but irritating in perilous jumping sections. The Last Guardian's sedate pace mitigates a lot of these problems, however. If the game wanted me to make sudden reactive movements or engage in combat the controls and framerate dips would be a functional problem rather than, as it is, an aesthetic one.

This is a vital distinction. While it is a deep shame that after all this time The Last Guardian should suffer performance issues, I am thoroughly glad to have played it, and would recommend the game to anyone. I've deliberately shied away from mentioning mechanical and narrative specifics - these things are better kept secret - but know that there is a complete story here with some great surprises. The Last Guardian is a fulfilling and emotional adventure, and while framerate problems must deny it the full five stars, but there is nothing else like Trico in games. I wish I could wake up in that cave again to experience the journey fresh. Treasure those first moments, they are the start of a beautiful friendship.