Never trust outward looks. Or first impressions. Do not trust second impressions either, for that matter. Things can be deceiving, and not always by chance. So when you see a game called The Secrets of Da Vinci: The Forbidden Manuscript, do not assume that it is adapted from Dan Brown's bestselling novel – it isn't. Do not assume that it's nothing more than a rip-off, trying to ride the franchise's popularity at the time of the movie's release – it isn't either. And do not think that because the title refers to a "forbidden manuscript", the game involves dark and forbidden secrets – it doesn't. Oh, wait a minute; does this mean the second impression might not have been completely unfounded after all? Indeed not, but only as far as the title is concerned. Is your head spinning already? Good! You're getting in the right frame of mind for the intrigue the game offers.

The year is 1522, three years after Leonardo da Vinci, arguably the greatest mind of the western world, died in France. The story begins as a young Italian artist named Valdo arrives at Cloux manor, the master's final residence, next to the city of Amboise where king François I holds his court. Valdo has been hired to discover a mysterious codex that Leonardo is rumoured to have hidden on the estate before his death. Dissimulations abound: Valdo has been told to keep his mission secret, claiming instead to have come to study Leonardo's machines and to look for one of his old sketches, while his employer only contacts him through letters which he never signs. The manor's current inhabitant, Marie de la Bourdaisière, known as Babou to her friends, is too beautiful and clever to be completely trustworthy, and even the estate's caretaker probably knows more than he is letting on. But the master dissimulator is definitely Leonardo himself, who has carefully hidden the clues leading to the manuscript.

The Secrets of Da Vinci was co-designed by Kheops Studio and Totm Studio, who collaborated previously on ECHO: Secrets of the Lost Cavern, and the Kheops touch is clear from the first. Trying out a new Kheops game is pretty much like doing a physical, going over the same important things with the same general characteristics — ("The point and click interface? Still functional! And the obligatory gunpowder-making sequence? Hasn't aged one bit!") — with one notable difference: things keep improving over time. Another frequent Kheops collaborator, Mzone, the graphics studio that takes delight in disproving reviewers who proclaim first-person node-based games too antiquated, delivers a superb rendition of the manor and its park. The museum now in charge of the estate was actually involved in the design of the game, to ensure historically accurate depictions. Fully animated cinematics are well done but unfortunately rather scarce, often replaced by drawings. The music tries to capture the mood of the time, and is eminently hummable; a sometimes faulty implementation, however, makes cues unpleasantly overlap from time to time.

But, of course, the feature every Kheops fan is waiting for is the inventory. Well, it is still there, tabs and all, and still necessary as Valdo collects quite an impressive collection of items, from a signet ring to freshly-cut logs, in his seemingly bottomless pockets. But the system has undergone three major improvements over Kheops' previous games. First, items are automatically put in your inventory when you pick them up, instead of piling together in a waiting zone. The game even tries to be clever; for instance, if you use a handle on a machine and then get it back, it will be put back where you had originally stored it. The system doesn't always work, and items sometimes end up in an unexpected slot, but it is still a convenient feature. Second, you can't combine items in your inventory any more. This does not mean that it is no longer possible to combine things, but it must now be done in the proper place – for instance, on the table where Leonardo kept his chemical apparatus if you want to brew something. You never have to go looking for illogical or hard to find locations, as was the case in ECHO; it always makes complete sense, and contributes to making the puzzles more realistic. The third improvement deals with the way more than one of the same item is handled. Instead of imposing the same arbitrary limit for all items, the game lets you pick up as many as is needed for a "standard" playthrough, so most of the time you won't have to go back to where the item was to get more, while not overcrowding your inventory with things you'll never use. Still, being heavily non-linear and featuring optional puzzles and alternate solutions, the game can't always predict exactly what you may need, but it works well enough for that never to feel cumbersome.

The reason this works is that puzzles never get repetitive. With such a system, your inventory would have been overfilling with clay in Return to Mysterious Island or plants in VOYAGE. Not so with The Secrets of Da Vinci. The game does not rely on making you do the same thing over and over again, maintaining a constant freshness throughout. The puzzles are varied, often focusing on getting Leonardo's machines to work (after understanding what their purpose is), solving riddles, preparing various chemicals and useful items, as well as some puzzles solved through interactive sketches. Many of them can be solved at any time during the span of the game (one night and three days), and some can be left unsolved, or be solved more easily by buying items from the caretaker – at a cost to both your finances and self-esteem, of course. But you will have to solve the vast majority of the puzzles to complete the game. I prefer it this way, as it means that, while remaining free to decide when and how you solve things, you will not finish the game with the frustrating feeling of having left most of the puzzles untouched. As usual with Kheops' games, a score system keeps track of your successes – but again it doesn't fully do its job of encouraging replays, since no maximum score is offered as a goal to attain.