If you can imagine Battleships meets Sudoku then you'll have a broad idea of how Oliver Grégoire's intricate deduction game works. It's playable solitaire but with 2-4 players it can be played in either competitive or cooperative mode.
However you play, you're trying to deduce which of the five types of crop are on each space in the board. Each crop is numbered 1-5; and crops are always laid out onto terrain tiles, of which there are four different types. Each contiguous area of terrain can contain only one of each crop type, and the number on a crop cannot exceed the number of contiguous terrain tiles in an area. That means each area of terrain could comprise 1-5 tiles. The only other stipulations are that terrain areas cannot be orthogonally or diagonally adjacent to areas of the same terrain and identical crops cannot be adjacent.
At the heart of Tiwanaku is an elaborate looking contraption: the Pachamama wheel. The game comes with 20 large cog-shaped cards; some designed for a short game, some for a longer game. You choose a cog but must take care only to look at its reverse side. That gives you set up information: how many of each terrain tile will be in the game, and what land tiles and crops are visible at the start. Once you've set up the board based on this information, you fit the cog into the Pachamama wheel. This can be a bit fiddly because you need to undo the pin at the centre of the contraption before you can slide the cog into place.
Depending on the number of players, you have 3-5 meeples. On your turn you can move a new meeple from any edge of the board to any location you can reach orthogonally, provided your path isn't blocked by another meeple. Tiles with a terrain tile and a crop don't inhibit movement but your movement ends if you reach a terrain tile that doesn't have a crop revealed on it. Alternatively, you can move by one square one of your meeples that's already on the board.
If your meeple ends its move on a space with no terrain tile, you discover that the strange wheel-like contraption isn't merely a gimmick. You turn the Pachamama wheels so that they match the symbols on the row and column corresponding to the space you are on and you open the left-hand window. That magically reveals the terrain type for that location. When you Discover a terrain, you score a point for every marker you have at the same level on the scoring track. This method of scoring rewards diversification: you stand to score more points discovering different terrain types than by homing in on one specific terrain.
But of course, Tiwanaku is a deduction game. You can each turn 'Predict' what crop should be on any and all the tiles your meeples are on. You check the answers by opening the 'Divination' window on the right hand side of the Pachamama wheel. Get your Divinations right and you'll score points but as soon as you get one wrong your turn ends, and you lose points. That means you need to deduce the correct crop from the situation on the board. Often you'll only have sufficient information to make an educated guess - perhaps having narrowed the possibilities down to a choice between two possible crops. It's up to you whether to take a push-your-luck gamble or wait for certainty... And as with scoring for Discovery, you're rewarded for diversity: you can only collect one token representing each crop type. That means there's a potentially tough decision to take about when to cash your tokens in: you'll score notably more for a full set of five different crops but your prospects of collecting the fourth and fifth crop in your set are much reduced.
Aside from the marvellous Pachamama wheel, the standout feature of Tiwanaku is the tactical element over where you position your meeples. You aren't just trying to score for correct deductions, you also need to position your meeples so that they give you access to tiles where you can make those deductions; and likewise, in a competitive game, you will want to position your meeples so that they block opponents from swooping in with high-scoring predictions.
Tho' the game plays well solitaire, we didn't find the cooperative game as enjoyable as the competitive mode. Tiwanaku scales well for different player counts but it particularly shines as a tactical competitive two-player game. Unless the players suffer from Analysis Paralysis (AP), games play quickly. Almost all of our plays at Board's Eye View have come in at under 30 minutes, and that includes up to 5 minutes of set-up time.
Publishers Sit Down! have done a great job with the production of Tiwanaku. The cardboard components in the standard retail version of the game are first rate. Tho' it's essentially an abstract game, there's a pre-Columbian theme that comes through strongly in Raphael Samakh's art and, of course, in that captivating Pachamama wheel. As a deduction game, comparisons are bound to made with Cryptid (Osprey) but Tiwanaku is a very different game and one with even broader appeal.