INFO1113 COMP9003: Object-Oriented Programming - Assignment: Chess Board Against AI
INFO1113 / COMP9003 Assignment
This assignment is worth 1 8% of your final grade .
Task Description In this assignment, you will create a game in the Java programming language using the Processing library for graphics and gradle as a dependency manager . In the game, the player must be able to move chess pieces on a chess board in order to play against an AI , ultimately capturing the opponent’s p ieces and executing a strategy to checkmate the opponent’s king . You have been given the task of developing a prototype of the game. A full description of gameplay mechanics and entities can be found below. An artist has created a simple demonstration of the game and has posted it on your online forum (Ed). You can also play a similar game here . You are encouraged to ask questions on Ed under the assignments category if you are unsure of the specification – but staff members will not be able to do any coding or debugging in this assignment for you. As with any assignment, make sure that your work is your own, and do not share your code or solutions with other students. Working on your assignment You have been given a scaffold which will help you get started with this assignment. You can download the scaffold ont o your own computer and invoke gradle build to compile and resolve dependencies. You will be using the Processing library within your project to allow you to create a window and draw graphics. You can access the documentation from here .
Gameplay The game contains a number of entities that will need to be implemented within your application. Board The board consists of a grid of tiles 14x14 . Each tile is 48x48 pixels , so the total is 672x672 pixels . However, t here are 120 pixels on the right sidebar reserved for information such as timers showing the number of minutes and seconds remaining on each player’s c lock, and warnings or other messages for the user . The window size is therefore 672x792. The board is arranged in a checkerboard pattern as below with alternating black and white tiles. These are fixed and do not change. Pieces sit atop these tiles, and th e tiles may change colour shade to indicate highlights for particular reasons.
There are 4 main types of highlights : • Blue – the player clicked on a piece, and it is able to move to this square. • Light red – the currently selected piece can move to this square, capturing the current piece there • Green – the player’s currently selected piece • Yellow – the last piece to move, and the square it came from • Dark red – the king on this square is currently i n check, or checkmate has occurred (pieces that contribute to the checkmate are highlighted in light red) The piece layout is defined in a file named in the “layout” attribute of the JSON configuration file described below.
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Page 3 of 11 Config The config file is in located in config.json in the root directory of the project. Use the simple json library to read it. Sample config and level files are provided in the scaffold. The config sample as shown to the left, contains the name of the layout file. Th is is also located in the root directory of the project. The layout file will contain a grid of text characters , where each character represents the piece that should be in that cell . Uppercase characters are for black, and lowercase are for white. See the table below.
Empty spaces are empty tiles. All maps used for marking will be valid, but you should write your own tests for invalid maps and handle them as you see fit. The “ time_controls ” section contains the amount of time to be give n to player 1 and player 2 (player 2 is the computer - cpu). Seconds it the total time they start with, which is consumed while they are thinking about a move. The “increment” is a number in seconds added to their remaining time once they make a move . The “player_colour ” property denotes the colour of the pieces of player 1 (the human player) . It should either have the value “white” or “black” . If player 1 is white, then player 2 is black. If player 1 is black, then player 2 is white. Whoever is white has the first move , as in regular chess . Layout file See page 5 for images of movement Black White Chess piece Value Sprites Movement P p Pawn 1 One space forward. Captures diagonally only. If blocked, cannot move. R r Rook 5.25 Horizontally and vertically. N n Knight 2 2 squares vertical, 1 horizontal, or vice versa B b Bishop 3.625 Diagonally in any direction. H h Archbishop 7.5 Like Knight + Bishop C c Camel 2 3 squares vertical, 1 horizontal, or vice versa G g General/Guard 5 Like Knight + King A a Amazon 12 Like Knight + Bishop + Rook K k King ∞ 1 space in any direction. Cannot move into danger. E e Chanc ellor 8.5 Like Knight + Rook Q q Queen 9.5 Like Bishop + Rook
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Page 4 of 11 Movement The “piece_movement_speed” property in the config denotes how fast in pixels per frame a piece move should occur. This is limited by the “max_movement_time”, a number in seconds that the movement time should not exceed. If the movement would exceed this amount of time, the speed is increased to ensure it doesn’t take longer. Moves occur at a constant speed, with the chess piece smoothly transitioning in a straight line from its original position to its new position. To trigger a move, the player must first select a piece by clicking on the cell it’s located in. Then, click to the cell the piece should move to. If the player instead selects one of their other pieces, then that piece becomes selected instead. If the player clicks on the selected piece again, or an invalid move, it becomes unselected. Normal movement of pieces is described in the table abo ve. The king, queen, bishop, knight, rook and pawn all have the same movement as in regular 8x8 chess. For the purposes of pawn movement, “forward” is considered going up the board for the human player, and going down the board for the computer player. In addition, be mindful of the following special moves. Special moves : • A pawn can move two squares forward if it is located on 2nd row from the top or bottom of the board (rank 2 and rank 13), and has not moved before. • A king may perform a ‘castling’ move if it has not moved before, which allows it to move two squares horizontally in either direction so long as there is also a rook towards the direction it will move (on the same rank) , and that rook hasn’t moved. When this move is performed, the rook is placed on the other side of the king, adjacent to it. • Pawn promotion: When a pawn reaches the 8th rank (ie. when it crosses the halfway point on the 14x14 board), then it is promoted to a queen. It immediately turns into a queen and can be use d as such in all subsequent moves Only a camel or knight move may jump over pieces (or the rook when castling) , and a player may not move a piece onto a cell already containing one of their own pieces. If a move causes the piece to enter a tile containing one of the opponent’s pieces, the opponent’s piece is ‘captured’ and removed from the board. All pieces captur e on the same tiles as their regular movement, with the only exception being pawns which capture diagonally forwards instead , if there is a piece there. This is the only time they are allowed to move diagonally. If there is a piece directly in front of a pawn , it is blocked and cannot m ove to the cell occupied by that piece . Examples of possible moves for each piece are shown below. INFO1113
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Figure 1: Archbishop movement Figure 2: Amazon movement Figure 3: Bishop movement
Figure 4: General/Guard movement Figure 5: Camel movement Figure 6: Rook movement
Figure 7: Knight movement Figure 8: King movement. The king cannot move to squares controlled by an opponent's piece. Figure 9: Chancellor movement. The camel and generals block movement in the left direction, but knight moves can still jump over (same for other knight combinations ).
Figure 10: Pawn movement. The pawn can only move diagonally when capturing and cannot move directly forward if blocked. Figure 11: Queen movement
Check and Checkmate If after a move, a king is under attack, the king is said to be in ‘check’. Under this circumstance, the player whose king is in check must do one of the following (all must already be legal moves): • Move their king to a safe square • Move a piece to block the attack • Capture the attacking piece
This is because otherwise, the player would lose their king on the next turn, and therefore lose the game. If none of these possibilities are available, then the player has been checkmated – there is no move available to them that would save their king, and they have lost. When check occurs, the king’s square is highlighted in dark red , and the message “Check!” appears i n the right sidebar . If a player attempts to make an otherwise legal move that doesn’t protect their king, display a message on the right sidebar : “You must defend your king !”, and the highlighted cell the king is on will flash 3 times with a duration of 0 .5 seconds each. A player cannot make a move that would result in their king coming under attack. This could be any of either: • Moving the king to a square which is under attack by the opponent • Moving a piece that is blocking an attack on their king by the opponent (this piece is said to be ‘pinned’) Illegal moves due to check or pins should not be highlighted as blue tiles when selecting a piece to potentially move it – only legal moves should be highlighted.
Computer AI movement The way the computer player determines moves is up to you. It can be as simple as choosing a move randomly out of all available legal moves. However, you should try and make it at least a bit intelligent. For example, here is guidance on some basic rules you might want to have: • Capture a piece if the piece’s value is higher than the capturing piece, and if multiple such options exist, choose the one with the highest diffe rence Figure 12: The black king is in check due to the white chancello r. Black cannot move their king, their only option is to move their General or Amazon to block (assuming there is no piece off -screen that can capture the white chancellor ). Figure 13: The selected pawn is pi nned by the archbishop, so cannot move. However if the archbishop was one space closer to it diagonally, then the pawn would be able to capture the archbishop but not move straight forward. If the king was on the square one space below where it currently i s, then the camel would be pinned by the bishop.
• If a piece is threatened to be captured by a piece of lower value (or any piece if the threatened one is undefended) , move it • Prefer to only move to squares that are not under attack by a piece of lower value (or even a piece of higher or equal value if the square is undefended) – let’s call these ‘safe squares’ • If possible , attack the opponent’s king or a square adjacent to it if it’s not already under attack • If possible, checkmate the opponent’s king • If all else fails, choose a random move (pre fer safe squares, but it’s possible none may be available) Win and lose conditions The game ends when either one player runs out of time, or their king is checkmated. Then other player wins . If the human player wins by checkmate , display a message saying “You w on by checkmate ” in the right sidebar . If the human player wins due to the timer, display instead “You won on time”. If the human player loses by checkmate , display a message saying “ You los t by checkmate ” in the right sidebar . If instead the cause was the timer, display “You lost on time”. The player can also resign the game by pressing ‘escape’ on the keyboard. The game ends and the message “You resigned” is displayed in the right sidebar . When the game ends, t he board remains intact and frozen so that the player cannot make any moves (but may restart the game with the key press ‘r’ ). If checkmate occurred, the bo ard should highlight the king of the checkmated player in red and the pieces contributing to checkmate in orange . Pieces contributing to checkmate are defined as a piece that is either attacking the king or one of the empty squares adjacent to it, or defen ding a piece that the king could otherwise capture. For each such square, there should onl y be one piece highlighted. If there are no legal moves for a player, then the game is considered a draw and enters the end state. Display the message “Stalemate – draw”.
Application Your application will need to adhere to the following specifications: • The window must have dimensions 672x792 • The game must maintain a frame rate of 60 frames per second. • Your application must be able to compile and run on any the univer sity lab machines (or Ubuntu VM) using gradle build & gradle run. Failure to do so, will result in 0% for Final Code Submission. • Your program must not exhibit any memory leak. Figure 14: The white king is checkmated. The contributing pieces are the archbishop and two pawns. INFO1113
Page 8 of 11 • You must use the processing library (specifically processing.core and processin g.data), you cannot use any other framework such as javafx, awt or jogl You have been provided a /resources folder which your code can access directly (please use a relative path) . These assets are loadable using the loadImage method attached to the PApplet type. Please refer to the processing documentation when loading and drawing an image. You may decide to modify these sprites if you wish to customise your game. You will be required to create your own sprites for any extensi ons you want to implement.
Extension The extension is worth 2 marks maximum . For an extension, you can choose to implement one of the following : • New piece type with different movement and/or special behaviour • Start menu to select options without having to change the config file • More complex computer AI (specify difficulty in config ?) • Option for 2 -player in config (two human players) • Option for fog of war chess in config ( Tiles not able to be moved to are greyed out. T he only pieces of the opponent’s that are visible are those which are present on tiles available to be moved to. Game ends upon king capture.) • Sound effects • Expan dable resizable board (drag corners to change game resolution) • More pawn promotion options rather than just promote to queen – user can choose while in - game • Allow pre -moves (and /or drag and drop pieces rather than just click to move) • Allow different types of new configurable pieces (combinations) within the json config file , and what their symbol would be in the layout • Multiple levels specified in the config for the purpose of solving chess puzzles / problems. OR, a feature you come up with which is of a si milar or higher level of complexity (ask your tutor) Please ensure you submit a config and level layout file with the features of your extension , and ensure the extension doesn’t break any of the default behaviour . Also, describe your extension functionali ty in the report.
