Even the most mundane, everyday things can seem full of mystery and adventure when you're a kid. Especially when you have a like-minded friend to bounce ideas off and encourage your flights of fancy. Knights & Bikes channels this familiar childhood experience in a knock-about co-operative (but you can still play it solo) adventure that remains endlessly charming even when its core mechanics don't join in the fun.

Nessa is a stowaway on a boat that's just docked at the holiday island home of Demelza. Quickly, the two girls meet and, in that way only children can do, become firm friends almost instantly. Nessa is slightly older and seemingly orphaned; Demelza lives in the island's caravan park run by her single dad, who is struggling to keep the business afloat. The pair seize the opportunity to escape into each other's imaginations, setting off on a grand adventure to recover the island's legendary buried treasure and, Demelza hopes, use it to reverse her father's financial misfortune.

The girls may have a treasure map to guide them, but things aren't quite so straightforward as realizing X marks the spot. Getting around town is a challenge. Nessa and Demelza can run--and if you hold down the run button they'll do that thing kids do where they spread their arms like wings and yell "Vrrrrrrrmmmm!" like they're a plane arcing through the air--but it's often not entirely clear where they ought to be running to. Luckily, Demelza's pet goose, Honkers, has a good nose for direction and will run off in the right direction, honking his little heart out if the girls fall behind. Oh, and don't worry, you can absolutely pet the goose.

Early on Nessa and Demelza procure the eponymous bikes which allow them to zip around the island much faster than on foot. The bikes can be upgraded, too, with all kinds of handlebar grips, paint jobs, spoke decorations, and so on. All of these are purely cosmetic, save for one--a particular set of wheels that lets the girls traverse pools of mud that would otherwise be blocking their progress. Cycling around the island is hugely entertaining in itself, not because it's especially interesting to navigate the many crisscrossing paths connecting the handful of major points of interest, but because the presentation does such a great job of capturing the carefree abandon these girls are feeling. You mash to pedal and build up momentum then hold down the button for a short burst of extra speed, all the while the girls are hooting and howling and, it must be said, not necessarily obeying strict road safety procedures.

Their adventure takes them from the caravan park to a mini golf course that doubles as the site of some historical battle to a maze-like scrapyard that transforms into a terrifying dungeon with seemingly no way out; to a hiking trail through the woods that twists and turns back in on itself in the manner of other more famous Lost Woods. Every step of the way the girls imbue the world with unwarranted but understandable wonder. The history book the local librarian is reading is obviously full of clues to the whereabouts of the treasure. That old man with a beard is very probably a wizard. And, clearly, every stroke of misfortune they encounter is a sign of the horrible curse afflicting the island.

It's all great fun. The (probably) consensual hallucinations of the two girls are for the most part light and breezy and carry them headlong into one thrilling scrape after another. Their humour is infectious and their bonds of friendship, forged so fast in the fire of fantasy, are never in doubt. They're both such superbly written characters, flinging one-liners at each other and building upon the other's latest witty invention. And they're vividly expressive, each new close-up of their comically contorted faces frozen in shock, disgust, awe or sly realization will never fail to bring a smile to your lips.

Where Knights & Bikes falters is in the moment to moment, the rote combat and light puzzling that knits together its seat-of-the-pants dash through childhood curiosity. Each girl finds three pieces of gear over the course of the game and these are used to both fend off enemies and negotiate numerous environmental puzzles. Nessa's water bombs, for example, can be thrown to deal damage to enemies, extinguish fires (and do extra damage to fire-based enemies) and, when splatted into a puddle on the ground, conduct electricity.

But combat is mostly trivial. Enemies aren't especially hard to defeat and the girls can heal each other (via a cute high-five) as long as they have enough of the bandages that drop in consistently plentiful amounts. Combat has the same knock-about energy that infuses the rest of the game, so it's sort of fun to button-mash your way through. But it's never interesting enough to look forward to.

The puzzles fare slightly better. There were a few occasions where I had to pause for a minute to think about what I needed to do next to progress. And I always enjoyed watching the next nonsensical triggered event play out after solving a puzzle even if I wasn't always sure what I was trying to accomplish. Most of the time I just chuckled and wondered what was going to happen next.

Remarkably, for a game clearly designed for two-player cooperative play (locally or online), it works well when played solo. Here, you can switch between the two girls whenever you wish and the capable AI will assume control of the other. In combat, the AI controlled girl will use her abilities effectively and, even more impressively, when required to help solve a puzzle she'll smartly move to the right spot and perform whatever is necessary. Even if you don't have a co-op partner, you're not really missing out on much.

Knights & Bikes was created by a small team featuring several people who worked on LittleBigPlanet and Tearaway, and you can feel that all these games share a similar creative vision. There's a kind of wide-eyed, rough and tumble spirit of adventure running through all three games that is hard to resist. Knights & Bikes is a wonderfully warm, effortlessly inviting experience that'll make you feel young again.