The 4×4 board

This page explains the rules of the game for 2 players on the 4×4 board.
If you want to know the rules of the game for 4 players, click here instead.

Cornerbase board

In order to play Cornerbase you only need to know:

Some of the FAQs and the N.B.s in these instructions may seem banal and redundant. They are used to eliminate all of the most common doubts that may arise. You may not need to read all of the FAQs, but if you want to read them we recommend to open the links only after giving at least a quick reading of the entire regulation.

 

Before starting

Every player has 8 pieces, each of them depicting a different letter. At the beginning of each game one of the players randomly chooses 4 letters. Both players discard the pieces that depict the non-chosen letters; those pieces won’t be used during the game.

Cornerbase piecesThe 8 letters of each player, the Black and the Red. The meaning of the letters is explained in the “Letters” section of these instructions.

N.B. For the first games we advise to play with the pieces P, S, J and D since they are the most intuitive; so, for now, you can avoid reading the explanation of A, T, M and H in the “Letters” section.

Each player takes the 4 pieces of the opponent, shuffles them and gives them back stacked with the letters facing down. The Red starts the game. At the beginning of your turn you draw one piece – if there are pieces to draw – from your stack, except for the first turn when you have to draw 2 pieces. You don’t have  to show the pieces in your hand to the opponent.

Placement: act of putting a piece from your hand on the board – with the letter facing up – in one of the squares marked with the same color of your pieces. In order to perform a placement, the square must be free.

During your turn you can perform a maximum of one placement. In case you end the turn with two pieces still in your hand (either because you couldn’t make a placement or you didn’t want to), the opponent will randomly choose one of the pieces in your hand and discard it. A discarded piece cannot re-enter the game.

FAQ: Is it possible to start a game with a number of pieces different from 4?
Quick answer: Yes, but if you are no expert player it is not a recommended practice.

FAQ: Can two players start a game with two different combinations of 4 pieces?
Quick answer: Yes, but the practice is strongly discouraged.

 

Win condition

You win the game if you occupy the enemy base with one of your pieces during your  turn. Your base is the corner-square whose adjacent squares are of the same color of your pieces.

Cornerbase basesIn the image above the two bases are highlighted: the base of the Red, at the bottom left, and the base of the Black, at the top right.
The playing field is depicted from the point of view of the Red.

FAQ: Do I win the game if a piece of mine occupies the enemy base during the opponent’s turn?
Quick answer: No.

 

Action



During your turn you can execute an action with each piece of your own color that is on the board, plus the possible placement of a new piece.

N.B. A placement is considered an action. Since every turn you can only perform one action per piece, you can’t make another action with the piece just placed during the turn.

FAQ: Is it mandatory to perform an action with each piece on the board?
Quick answer: No.

There are two kinds of actions: the movement and the skill activation. Each time that you want to perform an action with a piece, you must choose which type of action to execute.

  • Movement: it’s the orthogonal shift of the piece by one square upwards or to the right. The movement can be performed by any piece, independent of the letter that the piece depicts. The placement can be considered a type of movement. In order to perform a movement with a piece, the arrival square must be free.

Cornerbase movementCornerbase movement
P movement upwards.

Cornerbase movementCornerbase movement
P movement to the right.

N.B. You can’t shift pieces by one square to the left or downwards through a movement. A movement is performed only to the right or upwards.

N.B. Obviously the black pieces move as well upwards and to the right, but relatively to the Black’s perspective. For the Red, black pieces move to the left and downwards.

  • Skill activation: the skill depends on the letter depicted on the piece – see “Letters” section. Unlike the movement, which can only be executed upwards and to the right, skill activation can be executed in any direction (horizontally and vertically).

FAQ: Can I perform both the movement and the skill activation with one piece in one turn?
Quick answer: No.

FAQ: Is there a maximum number of pieces whose skills I can activate during my turn?
Quick answer: No, the only limit is the number of pieces of your color on the board.

 

First General Rule

During your turn, surrounded enemy pieces are destroyed.
A piece is said to be surrounded if all the adjacent squares are occupied by pieces of the opposite color. When a piece is destroyed it is removed from the board. A destroyed piece can’t re-enter the game.

piece surrounding piece surrounding piece surrounding
Examples of positions where a black piece is surrounded.
If it was the Red’s turn, the black piece would be destroyed.

N.B. During your turn the enemy piece is destroyed as soon as it is surrounded. You don’t wait the end of the turn to remove it from the board, you remove it immediately.

FAQ: If one of my pieces is surrounded during my turn, is it destroyed?
Quick answer: No.

 

Second General Rule

Before finishing your turn, you have to perform at least one action. Not performing any action during your turn – whether you don’t want to or you can’t – makes you lose the game. The placement of a new piece on the board is considered an action as well.

N.B. A piece can’t perform more than one action per turn, but it can be displaced by the skills of other pieces before and after performing its own action.

FAQ: If I have N pieces on the board, can I perform N actions with one piece?
Quick answer: No.

FAQ: Is it necessary to perform actions in a certain order?
Quick answer: No.

 

Consequence of the Second General Rule: a piece can suicide by getting out of the board through a regular action.

piece suicidepiece suicide
Moving to the right P gets out of the board and it suicides.

FAQWhy is it possibile to suicide your own pieces?
Quick answer: Because sometimes it can be useful or necessary.

FAQ: So, is it enough to have a piece on the edge of the board in order to make it suicide?
Quick answer: No.

 

Letters

This section explains the skills of each letter, not the movement, since the movement is the same for every letter!

D (Diagonal): it can shift diagonally by one square in any direction if the arrival square is free. It is the only piece that can “move” diagonally. It is the only piece whose skill is activated diagonally.

D skill
By activating its skill, D can shift to any of the highlighted squares (i.e. diagonally).

FAQ: Does D only move diagonally?
Quick answer: No, it can also move upwards and to the right like all the other pieces. “To move diagonally” is its skill.

 

J (Jump): it can shift horizontally or vertically by 2 squares. The presence of an obstacle in the adjacent square is necessary in order to activate the skill in that direction. It is also necessary that the arrival square is free.

J skill J skill
In the first image J can either jump P and land in B4 or jump S and land in D2.
In the second image J can either jump S and land in A3 or jump D and land in C1.
If, for instance, we removed the piece D in the second image then J could not land in C1 due to the lack of an obstacle to jump.

 

P (Push): it can push by one square an adjacent piece if the arrival square of the pushed piece is free. The square of P, the starting square and the arrival square of the pushed piece must be on the same row or column.

N.B. When P pushes anoather piece, P doesn’t move and it stays in its square.

N.B. If the arrival square of the pushed piece is occupied,  P cannot push that piece. Basically this means that P can’t push two or more pieces in a row.

P skill P skill
In the first image P can either push J in D1 or push D in B3.
In the second image red P can either push black P in A3 or D in C1.

pushing out of boardpushing out of board
If P pushes D, D gets out of the board and it gets destroyed.

N.B. P can also push out of the board a piece of the same color.

 

Switch (S): it can exchange its position with any adjacent piece.

S skillS skill
S exchanges position with P.

N.B. If an adjacent square is free then S can’t activate its skill in that direction (although maybe it can move there).

 

N.B. Except for D, each letter needs a target when activating its skill: J needs an adjacent piece in order to jump it, P needs an adjacent piece in order to push it, etc. The target can be both a piece of yours or an opponent’s piece, always.

 

Is this the first time you read these instructions?
If yes you can stop reading this section since we recommend to play your first game with the pieces P, J, S and D. You can jump directly to the last section: “Draw”.

 

Throw (T): it can throw an adjacent piece in another square adjacent to itself if the arrival square is free. The square of T, the starting square and the arrival square of the thrown piece must be on the same row or column.

T skill T skill
In the first image T can either throw M in C3 or throw H in B2.
In the second image T can either throw S in D3 or throw A in C2.

throwing out of the boardthrowing out of the board
If T throws J, J gets out of the board and it gets destroyed.

N.B. T can also throw out of the board a piece of the same color.

 

Attract (A): it can attract a piece to a square adjacent to itself if there are no other pieces between itself and the attracted piece. The square of A, the starting square and the arrival square of the attracted piece must be on the same row or column.


In the first image A can either attract M in C1 or attract T in B2.
In the second image A can either attract P in D2 or attract S in C3.

N.B. If A attracts a piece that is already in an adjacent square then it doesn’t count as an action since it doesn’t produce any change in the position of any piece on the board.

 

Mime (M): it can mime the skill of any adjacent piece.

M skill
M can mime either T or S. If it mimes T, M can throw T in D2 or throw S in C1.
If it mimes S, M can exchange position with either T or S.

N.B. If M mimes an adjacent piece but then it doesn’t use the copied skill then M hasn’t performed any action, since it hasn’t produced any change in the position of any piece on the board.

FAQ: Is it possible to mime the opponent’s M in order to copy the skill of a piece adjacent to it (which is not adjacent to my M)?
Quick answer: No.

 

Hack (H): it can activate the skill of an adjacent piece. This means that, for instance, with H you can activate the skill of an enemy piece (as if it was your piece during that turn) or you can make two actions with another piece of yours.

H skillH skill
H activates the skill of P and it make P push J upwards. J gets out of the board and it gets destroyed.

H skillH skillH skill
First H activates the skill of T to throw J in B3.
Then T, since it has still not performed an action (remember? it has thrown J thanks to H), throws H in C2.

FAQ: Is it possible to make another piece perform a movement through the skill activation of H?
Quick answer: No.

FAQ: Is it possible to activate the opponent’s H in order to activate the skill of a piece adjacent to it (which is not adjacent to my H)?
Quick answer: Yes.

 

Draw

You can propose to your opponent a draw only after finishing your turn. If the opponent performs any action then the draw proposal is automatically refused. If after performing one or more actions the opponent has second thoughts, then s/he will have to make a draw proposal now (after finishing her/his turn).

The next rule exists in order to avoid the most common stall situations that would bring the game to a draw:

Rule of the Repeated Position: if the position of all the pieces on the board remains unchanged at the beginning of two consecutive turns of one player, that player wins the game. To put it another way: if the position of all the pieces on the board remains unchanged at the end of two consecutive turns of one player, the opponent wins the game. The RRP doesn’t apply if between one turn and the other at least one piece (whether it’s an enemy piece or not) is discarded or destroyed.

rule of repeated positionrule of repeated position
The turn of the Black starts: s/he shifts D in C2 through skill activation and moves J in C1.

rule of repeated positionrule of repeated position
It’s now the Red’s turn: first s/he pushes J in D1 through skill activation of P, then using H s/he activates the skill of D and shifts D in B3.

rule of repeated positionrule of repeated position
If instead the Red had pushed J in D1 and shifted D in D3, he would have lost the game, since he would have restored all the pieces on the same position at the end of two consecutive turns of her/his (see the first of these 6 images).

FAQ: Therefore thanks to the RRP I can oblige my opponent to suicide a piece?
Quick answer: Yes, sometimes it is possible.

Despite the RRP, theoretical draw situations still exist, but they are way more infrequent.

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