Board

Typically, a board consists of an 8x8 grid of alternating colors, where play is restricted to just the half of the squares that are the same color.  While Checkers Touch provides traditional boards, the modern boards toss out the unused squares to make room for larger pieces.

Pieces

The pieces are initially laid out with the 12 pieces for the opponent filling the top 3 rows and 12 pieces for the user on the bottom 3 rows.

Who Goes First?

Normally the darker color (black in some boards, red in others) goes first.  However that's a bit limiting, so in Checkers Touch you can select any color you want.  For the first game you get to go first.  After that the side that loses goes first.

Movement

Pieces may only move diagonally in a forward direction, towards your opponent.  Upon reaching the last row, your piece becomes kinged, which affords it the capability to move backwards as well.  Movement is made by sliding the piece one square or if that square is occupied by an opponent, and the square behind them is open, jumping that piece and removing it the from board.  That is referred to as capturing an opponent. 

Important Note: If any capture move can be made, the player is required to jump and capture a piece.  Further, if after the capture the same piece can continue to capture pieces, it must continue.  If more than one capture presents itself, you are not required to chose the one with the longest path of consecutive captures.  You are, however, required to continue down which ever path you chose until no more captures are available to that piece.  If the piece was not previously kinged, then it must stop upon reaching the kings row and it then becomes king.  If the piece was previously a king, no stop is required in the kings row, and it must continue any legal captures.

Difficulty Levels

There are 4 main difficulty settings (Easy, Moderate, Challenging, and Hard) with 5 levels of granularity each, for a total of 20 different levels.  For each major level, there will be 1-5 small checker pieces next to the level indicating the sub-level.  The initial Setting is Moderate-3 and is represented by 3 pieces next to the word "moderate."

When the iPhone calculates a move, it does so recursively amongst the available moves giving point values for positive outcomes and subtracting any beneficial value a counter move might provide to the opponent.  For each level there is a limit on the depth of recursion, as well as the number of moves, that can be checked.  To make the game even more enjoyable, the iPhone will not always chose the best move it finds.  It will still play by the rules though and always jump if possible.

Level	Depth	Moves	Odds at 3rd sub-level
Easy	2	≤ 50	> 50% of picking the best move < 50% chance of picking up to the 5th best move
Moderate	3	≤ 150	> 650% of picking the best move < 35% chance of picking up to the 4th best move
Challenging	4	≤ 450	> 75% of picking the best move < 25% chance of picking up to the 3th best move
Hard	NA	NA	> 10% of picking the best move < 10% chance of picking the second best move *

The odds shown in the above table are for the median setting within that level and are further adjusted to make the Easy-1 easier than Easy-5

Easy: Only compares 2 levels deep, but will stop at a total of 50 moves checked.

Auto Adjust - On by default, this option will cause the difficulty to adjust over time to compensate for the skills of the player.  There is a win reward count next to the overall win count for each player.  For each win a side will gain a point, and if the other side already has accumulated rewards, those will be reduced by 1.  When either side reaches 3 rewards, the difficulty level will be adjusted.  If the iPhone wins, play will get slightly easier, otherwise play becomes more difficult.

Learning

After each game is complete, Checkers Touch will record the final outcome of every state visited during play. In addition to learning from moves it found, the iPhone will be learning from moves you make as well.  If during a future game, it discovers a move that has been visited before it will use the overall outcome (win:loss) ratio to determine if that is a favorable winning move, or a losing move.  During play the computer will chose winning moves over unvisited states.  Moves leading to a potential loss will be avoided unless all possible moves have an unfavorable win:loss ratio.

Since you are teaching the computer to play, it may repeat similar opening moves that you have used to win in the past.  As you find good countermeasures to those opening moves and win against them, they will fall out of favor.  In this way the iPhone will not play the same game twice.

Strategy

Try to acquire and maintain numerical advantage over your opponent.  Towards the end the side with a numerical advantage (more pieces), can afford to give up a piece if it forces the opponent to jump into a location to be immediately captured itself.  By trading captures in this fashion, you can maintain your numerical advantage.

Try to block your opponents from reaching your kings row and becoming king, while at the same time trying to get one your pieces kinged.  Because a king can move and capture backwards as well as forwards, it becomes twice as potent in the battle.

Keep in mind that jumping is mandatory in Checkers.  Checkers Touch only allows for legal moves**.  If a jump is available it will not allow you to make an illegal move.  Use this to your advantage, by looking for situations where a move you may make will force your opponent to weaken their position, either opening up their kings row, or exposing themselves to multiple capture allowing you to gain further numerical advantage.

Protect yourself from being captured by creating corridors for safe passage.

 

 

Keep track of how many turns you have left.  One way to win in Checkers is to have your opponent run out of legal moves.  If you have a solid wall and more turns left than your opponent, then try not to open up any more legal moves for your opponent when you move your pieces, and starve them of moves.

 

Finishing a game.

When the game progresses down to just a handful of pieces per side and all pieces are kings, it can become challenging to finish off.  Here are some tips.

Look for split pieces with a gap in between.  By moving in between the pieces, you force your opponent to chose which piece to save.  If you have numerical superiority, set up a trap along the edge of the board, and sacrifice a piece to force the opponent to jump into the trap, then capture back keeping your advantage.

Pin your opponent to the edge preventing them from moving without peril.  Here, neither piece can move without being captured by the other.

Here neither king can move in a forward direction without risking capture or being trapped against the side.

If your opponent decides to move forward and away from the edge it is immediately captured.  Your opponent might seek the safety of the edge to prevent you from being able to jump them.

If that happens, you can move out to trap them against the edge.  Now there is no immediate move they can make without being captured.

Be careful if there are other pieces on the board, because your opponent may be able to reverse the trap.

To get out of this, you can move a piece above yours, creating two corridors for escape.  Keep in mind that escaping this way will also free your opponent that was pinned against the wall.

Of course you don't have to rescue your piece.  With a free king you are free to move around and wait for you opponent to move the piece trapping yours.

Another approach might be to try to reverse the trap again.  Most likely your opponent won't fall for it, but it's worth a try.  It's important to note that it takes an odd number of moves to get there since we want to arrive last, forcing our opponent to have to move from a trapped state.  While it's no guarantee that the opponent will chose go back to this position, it's impossible for them to get there without an even number of moves.  Thus try to get them to return just before your last move which traps them in.

 

 

If your opponent offers up two pieces in a pattern similar to this, where you are the blue kinged piece (19) and they are the red pieces (11 & 18), move in between your opponents pieces (19 to 15).

This will force your opponent to chose which piece to save by moving it away from harm, allowing you to capture the other piece.

Be careful though, because this can be a trap if one of their pieces has backup.  In this image, The red team wants you to take the bait and split their pieces because then they can move the lower red piece to safety forcing you to jump into jeopardy of being captured as well.  If you have numerical advantage, these types of traps can be very effective.  You sacrifice one piece, but reduce your opponent by the same amount, keeping a numerical advantage.

 

Finishing in a draw.

If you get down to a tie of 3 or less pieces on each side, then selecting "New Game" will ask if you wish to end the game in a draw.

 

 

* Under the hardest level (Hard-5) the iPhone will always pick the best move it has.

** A new build will be posted later half of August with the ability to not enforce the official jump rule.