Yankai's Peak is hard. Like "getting stumped in the first batch of levels" hard, or "put the game aside and come back in a hour to try again" hard.

But it also can be immensely satisfying, the kind of puzzler where solutions and move possibilities click together in your head much like the game's dovetailing triangles, usually after a period of staring at a stage that seems impossible.

Yankai's Peak is one of the best puzzlers of 2017 thus far, thanks to its laser-focused design and deceptively simple mechanics explored in myriad clever challenges.

### Triangular logic

Kenny Sun already proved he could make a surprisingly diverse puzzler out of the three sides of a triangle; however, while Yankai's Triangle was simple to play and relatively simple to solve, Yankai's Peak is simple to play, and designed around a clockwork of rulesets and mechanics.

At its core, Yankai's Peak is a Sokoban-style puzzler with triangles. Every level is a tight grid crafted from triangular tiles, occupied by colored prisms. You flip end over end to navigate the stage, trying to maneuver the other prisms onto the same colored tiles and then reach your exit tile.

Sounds simple, but nothing in Yankai's Peak is ever as simple as it seems. Besides your basic style of movement, you can also tap a corner to anchor it to the grid, rotating around that anchor and creating an entirely new set of moves to consider.

Movement influences your every action in Yankai's Peak: where to position your prism, which direction to rotate, where to place an anchor, and, in turn, how that will affect all the other aforementioned variables. A single move can cause a chain reaction of shifting prisms, reorienting the entire grid, meaning every moment must be carefully planned. How must a prism be oriented so that you can push it into position without affecting its neighbors? Or how must you push it so that action also moves neighboring prisms as intended?

### Not as simple as it looks

Those are the kinds of tricky spatial calculations that Yankai's Peak asks you to make on every level, and an unlimited undo button lets you experiment and refine emerging solutions as many times as you require.

Alongside these consistent rules, a collection of additional mechanics keep the geometric brainteasers feeling fresh. Prisms that hover over empty space, tiles that change the colors of prisms, among others best discovered through play. Each one presents a small but game-changing wrinkle to the core gameplay.

It's through the combination of those mechanics and overall gameplay that Yankai's Peak shines. The stages grow more claustrophobic, more prisms to maneuver, new elements to learn, and yet your basic interactions are never more complicated than flipping around into position and placing anchors to rotate and shunt prisms. It's a cumulative exploration of that simple yet smartly-designed concept.

While you can also undo your moves, no hint system is waiting to help you. And while you're free to complete a chapter's levels at your leisure and in whatever order you prefer, you'll make no progress to new chapters if you get stumped. This lack of handholding means it can be frustratingly easy to get stuck when none of your attempts are working, and the other available levels are just as taxing, if not more so.

If you found games such as Snakebird, English Country Tune, and similar puzzlers too difficult, Yankai's Peak might prove to be equally frustrating.

Persevere however, and you'll find a puzzle game that constantly rewards you with clever spatial challenges and a satisfying sense of mastery.