Recent reviews by Rob Knight Gallo

There are plenty of comedic reviews, so I'll try to provide a more serious one instead.

5D chess (which is actually 4D, I'll explain that later) is a fascinating chess variant that utilizes the temporal dimension as as spatial and allows for the creation of simultaneous "parallel universes" of different chessboard configurations existing and having to be played. As a variant, it is arguably the most radical reinvention of chess that exists to this day as it not only changes the parameters of how chess is set-up, but in the process also changes how chess is fundamentally played.

Now onto the naming and fundamental concepts: Regular chess operates in a 3D environment, but the actual game lives in 2D. Namely, there are 2 spatial dimensions on the board, but the actual game when looked by an observer operates in an additional temporal dimension since time simply moves forward. In 5D chess, the game does in fact exist in 5 dimensions, but the actual chess is played in just 4. You can move in 2 spatial dimensions that correspond to the regular board, but you also have 2 bonus dimensions where chess pieces can move; you can move across time in timelike trajectories, either in the past or the future, or you can move across parallel spacelike trajectories between simultaneously existing chessboards. The 5th dimension is simply the regular irl time that the game operates and flows, similar to how normal 2D chess is embedded in the 3D framework I mentioned earlier.

This idea translates brilliantly in some truly ingenious reinvention of movement for each piece. The creator Conor Petersen put a significant effort in generalising (non-trivially) how each piece actually moves in the regular 2D chess. For example, the fact a bishop moves in diagonals is translated as simply a simultaneous move in 2 dimensions with equal steps in each. With this generalisation, one can extend bishops movement to include this variant where time and parallel-space jumping are accounted for.

The result is a game that is immensely complex, not so much because of the rules, but because it's very unintuitive and hard to visualise in your brain and spot patterns, which is obviously a major part of regular chess. Not only that, but as you play a single match more and more, the game naturally becomes more and more complicated and positions harder to calculate. That's natural, normal chess has this too, but in this game it becomes well-nigh impossible due to the enormous amount of parallel boards existing and how their interaction starts to become less and less obvious, making it very hard to predict movements or plan ahead.

The concept of winning changes considerably as well: checkmates no longer have to be about the known positions in which the enemy king is trapped, but positions in which the enemy king either is trapped and can't escape into a past/parallel board or positions the enemy king can't escape due to the fact you are actually checking a king in a past position. This consequence of the variant is by far the most impactful because even if one starts to find the rules and complications of the game more palatable, to actually be able to engineer a victory out of them is a truly daunting task.

Now, do I recommend this game? Yes I do wholeheartedly. It may not be for everyone due to its dizzying depth and complexity that might put some people off, and it may be less elegant than regular chess or other variants, but it's by far the most imaginative reinvention of the game I have ever come across, one of the best games where spacelike and timelike trajectories (in Physics terms) are illustrated in a very good way and it's just plainly a very interesting and innovative game. There's plenty of puzzles and sub-variants in game to try and have fun with as you learn the game and decent AI that is easy for the beginner levels and challenging enough for the higher ones.