The Search for Planet X

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Since 2016, astronomers have been searching for a distant planet to explain the unique orbits of observable objects in the solar system. Do you have what it takes to find Planet X? Players take on the role of astronomers, participating in this real scientific investigation. Use the free companion app to survey for objects and take other actions. Use the app results and the logic rul…
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Golden Pear


  • Artwork
  • Complexity
  • Replayability
  • Player Interaction
  • Component Quality

You Might Like

  • The app
  • The design and clear instructions
  • The one-player mode
  • The handicap system

Might Not Like

  • Player pawns – when everything else is so well-designed, these really stand out as sub-standard
  • On a multi-player game there’s not much interaction with others
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Since 2016, astronomers have been searching for a distant planet to explain the unique orbits of observable objects in the solar system. Do you have what it takes to find Planet X? Players take on the role of astronomers, participating in this real scientific investigation. Use the free companion app to survey for objects and take other actions. Use the app results and the logic rules to find objects, publish theories, and deduce where Planet X must be!

Two weeks after Christmas and whilst our other board game gifts are learned, loved and added to our regular play list, my wife has resolutely avoided The Search for Planet X.

So, is it a Christmas turkey?

Well, no. Whilst H may have given it the thumbs down, it certainly hasn’t gathered dust on the shelf. My eldest son in particular loves it and I’m only too happy to oblige his requests for another game. And that’s the truth of Planet X – it’s the Marmite (or if you’ll forgive me one last Christmas cliché, the brussels sprout) of the game world.

Who Will Enjoy It?

In essence, the game is an extended Logic Problem puzzle wrapped up into a board game. So, if logic is your thing, then you’re likely to get a lot out of Planet X. If not, it might leave you a little cold.

The Search for Planet X is a game for 1-4 players. It’s aimed at ages 13 and over, but B is a little younger and enjoys it immensely – although he’s still a little rusty on some of the tactics… We learnt the game by playing the solo version, working together as a team against the bot to solve the puzzle. And the one player mode is a real strength of the game, which myself and my two sons have gone back to again and again.

You need to download an accompanying app to play, but this is slick, easy to use and has some lovely sound effects, which really draw in the kids. B and I have only played the multi-player format a couple of times, but the handicap system is great. We can have a competitive, fairly even game without me having to throw it.

Game Play

The game board is good quality and really encapsulates the space theme. It’s double-sided, allowing you to play a standard and extended version. On the standard side, you have a solar system split into 12 sectors. You take on the role of an astronomer with a mission to map out the solar system by finding out what (comet, asteroid, dwarf planet, gas cloud, empty space or the elusive Planet X) is in each sector.

The instructions are very clear, so you can get up and running in minutes. TIP: You may find it helpful to start as we did, working together on a one player game to help each other learn tactics.

As I mentioned, there is a handicap system. You start the game by setting each player’s starting level and the app gives players a different number of clues according to the handicap. To help solve the puzzle you are told how many of each item there are in the solar system and have standard rules about the positioning of each item.

After each player has marked out their clues on their individual scoresheet (which again, is exceptionally well-designed) the game begins.

Players take it in turns to complete actions to uncover more clues to solve the puzzle. There are four actions you can take each time:

  • you can Survey to find out how many of your chosen item there are in a range of sectors,
  • you can Target a particular sector to find out which item is in it,
  • you can Research, which gives you an extra rule to help place items
  • and later in the game, you can Locate Planet X.

Each of these actions has an accompanying ‘cost’. That cost plays out in the number of moves your player pawn (definitely the weakest part of the game’s design) makes around the board. Rather than proceeding in a fixed turn order, the next player is the person who is furthest behind on the game board. Do you Target to get some definitive information? Or do you Research so you can have a few more turns before other players?

There are a couple of other game points, which keep things interesting. Every few moves you get to submit theories based on what you know, and there are conferences where the app gives all players more information about the location of Planet X – this can be a real leveller!

The game ends when one player successfully locates Planet X. However, the winner is not necessarily the one who finds Planet X first. Whilst this gives you a big lead, there are bonus points for submitting correct theories or identifying where other items are in the solar system. So, you might want to get tactical and take an extra couple of turns to find out more and earn more points.

The box suggests a game time of 60-75 minutes, but even on first plays, we’ve found a one or two player game much quicker. We’ve started out on fairly easy difficulty levels – which still presents reasonable challenge – but a game on Genius mode, where you don’t get any starting information, will take much longer!

So, it’s not a Christmas turkey, but is it a cracker?

I’m going to rate The Search for Planet X fairly highly for a certain type of player. The instructions and design are excellent – with the exception of those cheap and plasticky player pawns. It’s also extremely replayable. There are range of difficulty levels, you can handicap players and there are almost infinite different grid positions and clue selections defined by the app. Just make sure you don’t get it for someone who doesn’t like logic!

In January 2016, Konstantin Batygin and Michael E. Brown published their “Planet Nine” hypothesis. Using a computer model, they showed that a distant planet could explain the unique orbits of observable objects in the solar system. In The Search for Planet X, 1-4 players take on the role of astronomers, surveying the night sky and attempting to deduce the location of this hidden planet.

The Search for Planet X is an app-assisted deduction game. Players will be using logic to figure out where different celestial bodies are, publishing papers on their findings. Hopefully, being the first person to discover the elusive ‘Planet X’.

Setting Up The Solar System

First, decide whether you want to play in Standard Mode (12 sectors) or Expert Mode (18 sectors). Place the sun disc in the centre of the board and overlay the earth board so that the yellow arrow is pointing into sector 1.

Give each player all the pieces in one colour (1 player screen, 1 telescope miniature, 12 Theory Tokens) and 2 Target Tokens. If playing in Expert Mode, each player should also attach the ‘expert panel’ to the indicated slot in their player screen.

The 4 sides of the board are marked with a symbol relating to one of the four seasons. Each player should now take a note sheet relating to the side closest to them. These sheets show the night sky from their relative perspective, making it easier for the players to orient themselves.

Finally, before you start, at least one player will need to download the free companion app. If more than one person wants to use their device to play, you will need to generate a ‘game code’. This should be done by one person and then shared with everyone else.

Note: It’s VERY important you are all using the same game code, as this will determine the randomised location of each object in the sky. A different code means different locations.

The app will ask which side of the board you’re facing and give you some starting information (with more experienced players being given less).

The Laws Of Logic

Before we go any further, it’s worth understanding the logic rules that govern the various objects in this game (these are all listed on your player screen for easy access)

Asteroids (4) – These will always appear in pairs, which means they can be in two groups of 2 or one group of 4.

Comets (2) – Comets only appear in certain sectors (noted on your sheet). When surveying for them, you must start and end in one of these designated sectors.

Truly Empty Sectors (2) – These sectors have nothing in, which can be useful for helping deduce where other objects are.

Gas Clouds (2) – Each gas cloud will be next to at least 1 Truly Empty Sector.

Dwarf Planets (1) – The Dwarf Planet is never adjacent to Planet X.

Planet X (1) – Whenever you investigate Planet X’s sector, it will appear empty.

Using these rules, you will gradually be able to work out the pattern of the night sky and where each object is.

Note: The above values represent a Standard Mode game. When playing in Expert Mode, there will be 5 Truly Empty Sectors and 4 Dwarf Planets. These Dwarf Planets always appear in one of 6 possible patterns, which are shown on your player screen.

It’s also worth understanding the concept of the ‘visible sky’ – at all times, the Earth board will be covering up half of the sectors in the game. Whenever you Survey/Target, you can only ask for information in the half that is currently uncovered.

As players move, the Earth board will rotate to be in line with whoever is the furthest back. In this way, different sectors will be uncovered at different times, depending on where people are.

Time & Space

To begin, place each player’s telescope miniature into sector 1. The order can be random, but whoever is at the back of the queue will take the first turn.

The search for Planet X uses a time-track mechanism, where each action you do will cost you ‘time’, moving you forward a certain number of spaces. The player at the back will always go first, which means players might get to take multiple turns before you go again.

There are 4 main actions that you can take in your turn, all of which are done via the app

Survey for an object (? Time) – Decide which object you want to look for and choose a number of sectors in which to search (e.g., Asteroids in sectors 1-6). The app will tell you how many of those objects are in your selected area.

The smaller the area, the more time it costs

  • 1/2/3 Sectors (4 time)
  • 4/5/6 Sectors (3 time)
  • 7/8/9 Sectors (2 time) – this is only available in Expert Mode

Target A Sector (4 time) – Pick any sector in the visible sky and immediately learn what’s there. This also costs one of your Target Tokens, so it can only be done twice per game.

For instance, one of the topics might be ‘Comets & Asteroids’. You can then write this on your sheet to help with deductions.

You can’t do this action two turns in a row and it’s worth noting that the topics will only give one clue each, so there’s no need to research any of them more than once.

Locate Planet X (5 time) – Once you’re ready to locate Planet X, the app will ask you both which sector you think it’s in (this can be any sector, not just somewhere in the visible sky) and also what is located in both of the adjacent sectors.

If you get any of these answers wrong, the app will simply say ‘incorrect’, the game will continue. You can then make another guess on a future turn. If you’re right, finish your turn and move to the ‘End Of The Game’.

Game Theory

In certain sectors of the board, you will find a ‘Theory’ symbol. Whenever the yellow arrow on the Earth board points to or passes over, one of these, pause the game and carry out a ‘Theory Phase’.

During this phase, players will have a chance to submit theories as to where they think objects are located on the board. Each player can submit one theory in Standard Mode and up to two in Expert Mode.

To do this, each player takes the relevant theory token and simultaneously places it (face down) on the outer space (marked with a +) of the ‘Peer Review Track’ in their chosen sector. This can be the same sector as another player.

The Peer Review Track in each sector consists of 4 spaces (including the + space). As soon as any theory reaches the innermost space, flip it over and whoever placed it will consult the app. One of the options is ‘Peer Review’ and, when selected, the app will ask you which sector you are reviewing and what object you believe to be there.

If you’re correct, well done! All players can mark that object on their sheets. Any theories in the same sector can now be flipped, whether they made it to the innermost space or not.

If your theory is incorrect, remove your token from the game and advance your telescope one space on the time track as a penalty. Any other tokens in that sector will remain face down and face the same peer-review process once they reach the innermost space.

A Quick Conference

There is also a Conference symbol located in one of the sectors (two on the expert side of the board). As with the Theory symbol, when this is pointed at or passed over, pause the game, carry out a ‘Conference Phase’.

Each conference will give players a game-specific logic rule relating to Planet X. Everyone will receive the same piece of information, so it’s okay for one player to read this out to the table. Firstly, count how many spaces back you are from the person who triggered the end of the game (remember, locating Planet X costs 5 time, so they will always be ahead). Then, either…

  • Submit a Theory – if you are 1/2/3 spaces behind, you can submit one theory. If you are 4/5 spaces behind, you can submit two.
  • Locate Planet X – Follow the usual steps for locating Planet X, but don’t advance your telescope 5 spaces.

Once this is done, one player can click ‘Reveal Objects’ in the app. This will show you a list of each sector and what is there. Then move to final scoring.

Each correct theory you submitted will give you points, depending on the object –

  • Asteroid (2 points)
  • Comet (3 points)
  • Gas Cloud (4 points)
  • Dwarf Planet (2 points in Standard Mode/4 points in Expert Mode)

You also receive one bonus point for each sector in which you were the first person to submit a correct theory. If more than one player submitted correct theories at the same time, you both receive a point.

The Final

Finally, whoever correctly located Planet X (and triggered the end of the game) receives 10 points. Then, if anyone else located Planet X, consult the chart and receive points based on how far back you are.

  • 1 space (2 points)
  • 2 spaces (4 points)
  • 3 spaces (6 points)
  • 4 spaces (8 points)
  • 5 spaces (10 points)

Now add up your points and unsurprisingly, whoever has the most points wins! If there’s a tie, whoever discovered Planet X first wins.

And that’s how to play The Search For Planet X! This is a lovely little deduction game, with gorgeous production and brilliant app integration. It’s not for everyone, particularly as there’s very little interaction and (usually) a lot of time spent working things out in silence. However, if you’re in the market for a ‘thinky’ game, I’d definitely give this one a go.

If you’re in the market for another deduction game, why not try Cryptid or Awkward Guests.

Zatu Score


  • Artwork
  • Complexity
  • Replayability
  • Player Interaction
  • Component Quality

You might like

  • The app
  • The design and clear instructions
  • The one-player mode
  • The handicap system

Might not like

  • Player pawns when everything else is so well-designed, these really stand out as sub-standard
  • On a multi-player game theres not much interaction with others