Code viewer for World: Agent Hunter

// Cloned by Rajat Lashkare on 30 Oct 2023 from World "Complex World" by Starter user 
// Please leave this clone trail here.




// ==== Starter World =================================================================================================
// This code is designed for use on the Ancient Brain site.
// This code may be freely copied and edited by anyone on the Ancient Brain site.
// To include a working run of this program on another site, see the "Embed code" links provided on Ancient Brain.
// ====================================================================================================================



// =============================================================================================
// More complex starter World 
// 3d-effect Maze World (really a 2-D problem)
// Movement is on a semi-visible grid of squares 
//
// This more complex World shows:
// - Skybox
// - Internal maze (randomly drawn each time)
// - Enemy actively chases agent
// - Music/audio
// - 2D world (clone this and set show3d = false)
// - User keyboard control (clone this and comment out Mind actions to see)
// =============================================================================================


// =============================================================================================
// Scoring:
// Bad steps = steps where enemy is within one step of agent.
// Good steps = steps where enemy is further away. 
// Score = good steps as percentage of all steps.
//
// There are situations where agent is trapped and cannot move.
// If this happens, you score zero.
// =============================================================================================





// ===================================================================================================================
// === Start of tweaker's box ======================================================================================== 
// ===================================================================================================================

// The easiest things to modify are in this box.
// You should be able to change things in this box without being a JavaScript programmer.
// Go ahead and change some of these. What's the worst that could happen?


AB.clockTick = 100;

// Speed of run: Step every n milliseconds. Default 100.

AB.maxSteps = 1000;

// Length of run: Maximum length of run in steps. Default 1000.

AB.screenshotStep = 5;

// Take screenshot on this step. (All resources should have finished loading.) Default 50.

AB.pauseOnAgentCapture = true;

// This flag will stop the game when enemy catches the agent. If set to false, it will continue to run until the agent is trapped.


AB.bfsSearchReportOn = true;

//---- global constants: -------------------------------------------------------

const show3d = true;						// Switch between 3d and 2d view (both using Three.js) 


const TEXTURE_WALL = '/uploads/rajat33/wall128x128.png';
const TEXTURE_MAZE = '/uploads/rajat33/cratetex.png';
const TEXTURE_AGENT = '/uploads/rajat33/mcu.png';
const TEXTURE_ENEMY = '/uploads/rajat33/devil_new.png';

const TEXTURE_GROUND_1 = "/uploads/rajat33/cretebrick970.png";
const TEXTURE_GROUND_2 = "/uploads/rajat33/concrete516.png";

// credits:
// https://www.flaticon.com/free-icon/devil_2941796?term=enemy&related_id=2941796
// https://www.flaticon.com/free-icon/mcu_11892386
// https://opengameart.org/content/seamless-wall
// https://opengameart.org/content/simple-toon-wooden-crate-texture
// https://opengameart.org/content/seamless-concrete-tiles


const MUSIC_BACK = '/uploads/rajat33/space_line-27593.mp3';
const SOUND_ALARM = '/uploads/rajat33/winsquare-6993.mp3';

// credits:
// https://pixabay.com/sound-effects/space-line-27593/
// https://pixabay.com/sound-effects/winsquare-6993/



const gridsize = 40; //  25;						// number of squares along side of world	   

const NOBOXES = Math.trunc((gridsize * gridsize) / 4 );  // 10 
// density of maze - number of internal boxes
// (bug) use trunc or can get a non-integer 

const squaresize = 100;					// size of square in pixels

const MAXPOS = gridsize * squaresize;		// length of one side in pixels 

const SKYCOLOR = 0xddffdd;				// a number, not a string 


const startRadiusConst = MAXPOS * 0.8;		// distance from centre to start the camera at
const maxRadiusConst = MAXPOS * 10;		// maximum distance from camera we will render things  



//--- change ABWorld defaults: -------------------------------

ABHandler.MAXCAMERAPOS = maxRadiusConst;

ABHandler.GROUNDZERO = true;						// "ground" exists at altitude zero



//--- skybox: -------------------------------
// skybox is a collection of 6 files 
// x,y,z positive and negative faces have to be in certain order in the array 
// https://threejs.org/docs/#api/en/loaders/CubeTextureLoader 

const SKYBOX_ARRAY = [
    "/uploads/rajat33/hot_lf.png",
    "/uploads/rajat33/hot_rt.png",
    "/uploads/rajat33/hot_up.png",
    "/uploads/rajat33/hot_dn.png",
    "/uploads/rajat33/hot_ft.png",
    "/uploads/rajat33/hot_bk.png"
];


// hot lava world from below skybox, credit:
// https://opengameart.org/content/elyvisions-skyboxes?page=1


// space skybox, credit:
// http://en.spaceengine.org/forum/21-514-1
// x,y,z labelled differently

/*
 const SKYBOX_ARRAY = [										 
                "/uploads/starter/sky_pos_z.jpg",
                "/uploads/starter/sky_neg_z.jpg",
                "/uploads/starter/sky_pos_y.jpg",
                "/uploads/starter/sky_neg_y.jpg",
                "/uploads/starter/sky_pos_x.jpg",
                "/uploads/starter/sky_neg_x.jpg"
                ];
*/


// urban photographic skyboxes, credit:
// http://opengameart.org/content/urban-skyboxes

/*
 const SKYBOX_ARRAY = [										 
                "/uploads/starter/posx.jpg",
                "/uploads/starter/negx.jpg",
                "/uploads/starter/posy.jpg",
                "/uploads/starter/negy.jpg",
                "/uploads/starter/posz.jpg",
                "/uploads/starter/negz.jpg"
                ];
*/



// ===================================================================================================================
// === End of tweaker's box ==========================================================================================
// ===================================================================================================================


// You will need to be some sort of JavaScript programmer to change things below the tweaker's box.



//--- Mind can pick one of these actions -----------------

const ACTION_LEFT = 0;
const ACTION_RIGHT = 1;
const ACTION_UP = 2;
const ACTION_DOWN = 3;
const ACTION_STAYSTILL = 4;

// in initial view, (smaller-larger) on i axis is aligned with (left-right)
// in initial view, (smaller-larger) on j axis is aligned with (away from you - towards you)


// contents of a grid square

const GRID_BLANK = 0;
const GRID_WALL = 1;
const GRID_MAZE = 2;


var BOXHEIGHT;		// 3d or 2d box height 

var GRID = new Array(gridsize);			// can query GRID about whether squares are occupied, will in fact be initialised as a 2D array   
var BASE = new Array(gridsize);          // Base below the grid
var theagent, theenemy;

var wall_texture, agent_texture, enemy_texture, maze_texture;
var ground1_texture, ground2_texture;   // RL: Newly added from path tracking
var previousPathObjects = [];           // RL: Stores the projected path from Enemy to Agent from A* search. It is cleared and newly generated on every step.

// enemy and agent position on squares
var ei, ej, ai, aj;

var badsteps;
var goodsteps;


// For analytics and report
var aStarStatesSearched = 0;
var bfsSatatesSearched = 0;
var REPORT = {
    totalStates: 0,
    steps: []
};


function loadResources()		// asynchronous file loads - call initScene() when all finished 
{
    var loader1 = new THREE.TextureLoader();
    var loader2 = new THREE.TextureLoader();
    var loader3 = new THREE.TextureLoader();
    var loader4 = new THREE.TextureLoader();

    loader1.load(TEXTURE_WALL, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        wall_texture = thetexture;
        if (asynchFinished()) initScene();		// if all file loads have returned 
    });

    loader2.load(TEXTURE_AGENT, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        agent_texture = thetexture;
        if (asynchFinished()) initScene();
    });

    loader3.load(TEXTURE_ENEMY, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        enemy_texture = thetexture;
        if (asynchFinished()) initScene();
    });

    loader4.load(TEXTURE_MAZE, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        maze_texture = thetexture;
        if (asynchFinished()) initScene();
    });

    // RL: My code START

    var loader5 = new THREE.TextureLoader();
    var loader6 = new THREE.TextureLoader();

    loader5.load(TEXTURE_GROUND_1, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        ground1_texture = thetexture;
        if (asynchFinished()) initScene();
    });

    loader6.load(TEXTURE_GROUND_2, function (thetexture) {
        thetexture.minFilter = THREE.LinearFilter;
        ground2_texture = thetexture;
        if (asynchFinished()) initScene();
    });

    // RL: My code END

}

// RL:  Updated to check for ground1_texture & ground2_texture
function asynchFinished()		 // all file loads returned 
{
    if (wall_texture && agent_texture && enemy_texture && maze_texture && ground1_texture && ground2_texture) return true;
    else return false;
}




//--- grid system -------------------------------------------------------------------------------
// my numbering is 0 to gridsize-1

// RL: My code START

// Grid function that stores its poistion (i, j), object (wall / maze / base, etc), its neighbours (required for A*), type, and previous (parent grid object)
function Grid(i, j) {
    this.i = i;
    this.j = j;
    this.object = undefined;
    this.type = undefined;
    this.neighbours = [];
    this.previous = undefined;

    this.f = 0;
    this.g = 0;
    this.h = 0;

    this.setObject = function (object) {
        this.object = object;
    }

    this.setType = function (type) {
        this.type = type;
    }

    this.addNeighbours = function (grid) {
        var i = this.i;
        var j = this.j;
        if (i > 0) {
            this.neighbours.push(grid[i - 1][j]);
        }
        if (j > 0) {
            this.neighbours.push(grid[i][j - 1]);
        }
        if (i < gridsize - 1) {
            this.neighbours.push(grid[i + 1][j]);
        }
        if (j < gridsize - 1) {
            this.neighbours.push(grid[i][j + 1]);
        }
    }
}

// RL: My code END

function occupied(i, j)		// is this square occupied
{
    if ((ei == i) && (ej == j)) return true;		// variable objects 
    if ((ai == i) && (aj == j)) return true;

    if (GRID[i][j].type == GRID_WALL) return true;		// fixed objects	 
    if (GRID[i][j].type == GRID_MAZE) return true;

    return false;
}


// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates
// logically, coordinates are: y=0, x and z all positive (no negative)    
// logically my dimensions are all positive 0 to MAXPOS
// to centre everything on origin, subtract (MAXPOS/2) from all dimensions 

function translate(i, j, k = 0) {
    var v = new THREE.Vector3();

    v.y = k * squaresize;
    v.x = (i * squaresize) - (MAXPOS / 2);
    v.z = (j * squaresize) - (MAXPOS / 2);

    return v;
}

// RL: My code START

// Function to add new block to the scene
function addBlock(texture, position) {
    var shape, block;

    shape = new THREE.BoxGeometry(squaresize, BOXHEIGHT, squaresize);
    block = new THREE.Mesh(shape);
    block.material = new THREE.MeshBasicMaterial({ map: texture });

    if (position) {
        block.position.copy(position);
    }

    ABWorld.scene.add(block);
    return block;
}

// Function to update texture of existing block.
function updateBlock(texture, object) {
    object.material.map = texture;
    object.material.needsUpdate = true;
    return object;
}
// RL: My code END


function initScene()		// all file loads have returned 
{
    var i, j, shape, thecube, thebase;

    // set up GRID as 2D array

    for (i = 0; i < gridsize; i++) {
        GRID[i] = new Array(gridsize);
        BASE[i] = new Array(gridsize);      // RL: Initialized Base (game floor)

        for (j = 0; j < gridsize; j++) {
            GRID[i][j] = new Grid(i, j);    // RL: Initialized grid objects
            BASE[i][j] = new Grid(i, j);    // RL: Initialized base objects
        }
    }


    // set up walls

    for (i = 0; i < gridsize; i++)
        for (j = 0; j < gridsize; j++) {
            if ((i == 0) || (i == gridsize - 1) || (j == 0) || (j == gridsize - 1)) {
                GRID[i][j].setType(GRID_WALL);
                BASE[i][j].setType(GRID_WALL);

                thecube = addBlock(wall_texture, translate(i, j));        // translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 
                GRID[i][j].setObject(thecube);

                thebase = addBlock(wall_texture, translate(i, j, -1));
                BASE[i][j].setObject(thebase);
            }
            else {
                GRID[i][j].setType(GRID_BLANK);
                BASE[i][j].setType(GRID_WALL);  // Base is just a type of wall only!

                thebase = addBlock(ground1_texture, translate(i, j, -1));
                BASE[i][j].setObject(thebase);
            }
        }


    // set up maze 

    // RL: Note - here we are not checking if there was already a maze block present on randomly generated position(i, j)
    // there might be a scenario when boxes overalp on large grids, ignoring this case for now...
    for (var c = 1; c <= NOBOXES; c++) {
        i = AB.randomIntAtoB(1, gridsize - 2);		// inner squares are 1 to gridsize-2
        j = AB.randomIntAtoB(1, gridsize - 2);

        GRID[i][j].setType(GRID_MAZE);

        shape = new THREE.BoxGeometry(squaresize, BOXHEIGHT, squaresize);
        thecube = new THREE.Mesh(shape);
        thecube.material = new THREE.MeshBasicMaterial({ map: maze_texture });

        thecube.position.copy(translate(i, j)); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 
        ABWorld.scene.add(thecube);
        GRID[i][j].setObject(thecube);
    }


    // RL: Adding all neighbours in game space, excluding walls
    for (i = 1; i < gridsize - 1; i++) {
        for (j = 1; j < gridsize - 1; j++) {
            GRID[i][j].addNeighbours(GRID);

            // RL: For collecting stats
            if (GRID[i][j].type == GRID_BLANK) {
                // This is a valid state
                REPORT.totalStates++;
            }
        }
    }


    // set up enemy 
    // start in random location

    do {
        i = AB.randomIntAtoB(1, gridsize - 2);
        j = AB.randomIntAtoB(1, gridsize - 2);
    }
    while (occupied(i, j));  	  // search for empty square 

    ei = i;
    ej = j;

    shape = new THREE.BoxGeometry(squaresize, BOXHEIGHT, squaresize);
    theenemy = new THREE.Mesh(shape);
    theenemy.material = new THREE.MeshBasicMaterial({ map: enemy_texture });
    ABWorld.scene.add(theenemy);
    drawEnemy();



    // set up agent 
    // start in random location

    do {
        i = AB.randomIntAtoB(1, gridsize - 2);
        j = AB.randomIntAtoB(1, gridsize - 2);
    }
    while (occupied(i, j));  	  // search for empty square 

    ai = i;
    aj = j;

    shape = new THREE.BoxGeometry(squaresize, BOXHEIGHT, squaresize);
    theagent = new THREE.Mesh(shape);
    theagent.material = new THREE.MeshBasicMaterial({ map: agent_texture });
    ABWorld.scene.add(theagent);
    drawAgent();


    // finally skybox 
    // setting up skybox is simple 
    // just pass it array of 6 URLs and it does the asych load 

    ABWorld.scene.background = new THREE.CubeTextureLoader().load(SKYBOX_ARRAY, function () {
        ABWorld.render();

        AB.removeLoading();

        AB.runReady = true; 		// start the run loop
    });

}





// --- draw moving objects -----------------------------------


function drawEnemy()		// given ei, ej, draw it 
{
    theenemy.position.copy(translate(ei, ej)); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 

    ABWorld.lookat.copy(theenemy.position);	 		// if camera moving, look back at where the enemy is  
}


function drawAgent()		// given ai, aj, draw it 
{
    theagent.position.copy(translate(ai, aj)); 		  	// translate my (i,j) grid coordinates to three.js (x,y,z) coordinates 

    ABWorld.follow.copy(theagent.position);			// follow vector = agent position (for camera following agent)
}



// RL: --- A* algorithm -----------------------------------

// Helper method to remove element from array
function removeFromArray(arr, elem) {
    var x = arr.indexOf(elem);
    if (x > -1) {
        arr.splice(x, 1);
    }
}

// To calculate g(x) and h(x)
function getDistance(start, end) {
    return Math.abs(start.i - end.i) + Math.abs(start.j - end.j);
}

// Function returns the shortest path from start (enemy) to end (agent)
// RL: I have modified most of the code from A star Wrold and created below function.
function calculateAStarPath(start, end) {
    aStarStatesSearched = 0;
    // console.log("Enemy is at (", start.i, ", ", start.j, ")");
    // console.log("Agent is at (", end.i, ", ", end.j, ")");

    var aStarPath = [];

    var openSet = [];
    var closedSet = [];
    var pathNotFound = true;
    var winner;

    openSet.push(start);

    while (openSet.length > 0 && pathNotFound) {

        winner = openSet[0];
        for (var item of openSet) {
            if (item.f < winner.f) {
                winner = item;
            }
        }

        if (winner == end) {
            // console.log("TARGET FOUND!!");
            pathNotFound = false;
        }

        removeFromArray(openSet, winner);
        closedSet.push(winner);

        var neighbours = winner.neighbours;
        for (var neighbour of neighbours) {
            if (!closedSet.includes(neighbour) && neighbour.type == GRID_BLANK) {
                aStarStatesSearched++;
                var tempG = getDistance(start, winner);

                if (openSet.includes(neighbour)) {
                    if (tempG < neighbour.g) {
                        neighbour.g = tempG;
                    } else {
                        // RL: Continue as neighbour is already present in openSet with better g(x);
                        continue;
                    }
                } else {
                    neighbour.g = tempG;
                    openSet.push(neighbour);
                }

                neighbour.h = getDistance(neighbour, end);
                neighbour.f =  neighbour.g + neighbour.h;
                neighbour.previous = winner;
                
                if (neighbour == end) {
                    pathNotFound = false;
                    break;
                }
            }
        }
    }
    
    if (!pathNotFound) {
        var temp = winner;
        aStarPath.push(winner);
        while (temp.previous && temp.previous != start) {
            aStarPath.push(temp.previous);
            temp = temp.previous;
        }
    }

    return aStarPath;
}

// BFS Algorithm created for generating stats in comparison to A-star
function calculatePathUsingBFS(start, end) {
    bfsSatatesSearched = 0;

    var bfsPath = [];

    var openSet = [];
    var closedSet = [];
    var pathNotFound = true;
    var winner;

    openSet.push(start);

    while (openSet.length > 0 && pathNotFound) {

        winner = openSet.shift();

        if (winner == end) {
            // console.log("TARGET FOUND!!");
            pathNotFound = false;
        }

        closedSet.push(winner);

        var neighbours = winner.neighbours;
        for (var neighbour of neighbours) {
            if (!closedSet.includes(neighbour) && neighbour.type == GRID_BLANK) {
                if (!openSet.includes(neighbour)) {
                    bfsSatatesSearched++;
                    openSet.push(neighbour);
                    neighbour.previous = winner;
                    if (neighbour == end) {
                        pathNotFound = false;
                        break;
                    }
                }
            }
        }
    }

    if (!pathNotFound) {
        var temp = winner;
        bfsPath.push(winner);
        while (temp.previous && temp.previous != start) {
            bfsPath.push(temp.previous);
            temp = temp.previous;
        }
    }

    return bfsPath;
}

// --- take actions -----------------------------------

function moveLogicalEnemy() {

    // RL: Clearing the previously highlighted path
    while (previousPathObjects.length > 0) {
        var temp = previousPathObjects.shift();
        updateBlock(ground1_texture, temp);
    }

    // RL: Calcualte BFS Path as well for making comparison in report. This can be turned of by setting AB.bfsSearchReportOn = false;
    var pathBFS = [];
    if (AB.bfsSearchReportOn) {
        pathBFS = calculatePathUsingBFS(GRID[ei][ej], GRID[ai][aj]);
    }

    var path = calculateAStarPath(GRID[ei][ej], GRID[ai][aj]);
    
    // console.log(path);
    if (path.length > 0) {
        var nextPath = path[path.length - 1];

        // RL: Checking enemy is present on the next path. Walls and maze are ignored by the calculateAStarPath function
        if (!occupied(nextPath.i, nextPath.j)) {
            // Set next move
            ei = nextPath.i;
            ej = nextPath.j;
        }

        // RL: Updating blocks to highlight path on the base
        for (var pathObject of path) {
            var base = BASE[pathObject.i][pathObject.j];
            updateBlock(ground2_texture, base.object);
            previousPathObjects.push(base.object);
        }

    } else {
        // Ignore move as no path found!
    }
    
    // RL: COMMENTED EXISTING LOGIC FOR ENEMY MOVEMENT
    // move towards agent 
    // put some randomness in so it won't get stuck with barriers 

    //  var i, j;
    //  if ( ei < ai ) i = AB.randomIntAtoB(ei, ei+1); 
    //  if ( ei == ai ) i = ei; 
    //  if ( ei > ai ) i = AB.randomIntAtoB(ei-1, ei); 

    //  if ( ej < aj ) j = AB.randomIntAtoB(ej, ej+1); 
    //  if ( ej == aj ) j = ej; 
    //  if ( ej > aj ) j = AB.randomIntAtoB(ej-1, ej); 

    //  if ( ! occupied(i,j) )  	// if no obstacle then move, else just miss a turn
    //  {
    //   ei = i;
    //   ej = j;
    //  }

    // RL: For report generation
    var stepReport = {
        step: AB.step,
        aStarStatesSearched,
        aStarPathLength: path.length
    };

    if(AB.bfsSearchReportOn) {
        stepReport.bfsSatatesSearched = bfsSatatesSearched;
        stepReport.bfsPathLength = pathBFS.length;
    }

    REPORT.steps.push(stepReport);
}


function moveLogicalAgent(a)			// this is called by the infrastructure that gets action a from the Mind 
{
    var i = ai;
    var j = aj;

    if (a == ACTION_LEFT) i--;
    else if (a == ACTION_RIGHT) i++;
    else if (a == ACTION_UP) j++;
    else if (a == ACTION_DOWN) j--;

    if (!occupied(i, j)) {
        ai = i;
        aj = j;
    }
}




// --- key handling --------------------------------------------------------------------------------------
// This is hard to see while the Mind is also moving the agent:
// AB.mind.getAction() and AB.world.takeAction() are constantly running in a loop at the same time 
// have to turn off Mind actions to really see user key control 

// we will handle these keys: 

var OURKEYS = [37, 38, 39, 40];

function ourKeys(event) { return (OURKEYS.includes(event.keyCode)); }


function keyHandler(event) {
    if (!AB.runReady) return true; 		// not ready yet 

    // if not one of our special keys, send it to default key handling:

    if (!ourKeys(event)) return true;

    // else handle key and prevent default handling:

    if (event.keyCode == 37) moveLogicalAgent(ACTION_LEFT);
    if (event.keyCode == 38) moveLogicalAgent(ACTION_DOWN);
    if (event.keyCode == 39) moveLogicalAgent(ACTION_RIGHT);
    if (event.keyCode == 40) moveLogicalAgent(ACTION_UP);

    // when the World is embedded in an iframe in a page, we want arrow key events handled by World and not passed up to parent 

    event.stopPropagation(); event.preventDefault(); return false;
}





// --- score: -----------------------------------


function badstep()			// is the enemy within one square of the agent
{
    if ((Math.abs(ei - ai) < 2) && (Math.abs(ej - aj) < 2)) return true;
    else return false;
}


function agentBlocked()			// agent is blocked on all sides, run over
{
    return (occupied(ai - 1, aj) &&
        occupied(ai + 1, aj) &&
        occupied(ai, aj + 1) &&
        occupied(ai, aj - 1));
}

function agentCaught()			// enemy is standing on either side of agent
{
    return ((ai - 1 == ei && aj == ej) ||
        (ai + 1 == ei && aj == ej) ||
        (ai == ei && aj + 1 == ej) ||
        (ai == ei && aj - 1 == ej));
}


function updateStatusBefore(a)
// this is called before anyone has moved on this step, agent has just proposed an action
// update status to show old state and proposed move 
{
    var x = AB.world.getState();
    AB.msg(" Step: " + AB.step + " &nbsp; x = (" + x.toString() + ") &nbsp; a = (" + a + ") ");
}


function updateStatusAfter()		// agent and enemy have moved, can calculate score
{
    // new state after both have moved

    var y = AB.world.getState();
    var score = (goodsteps / AB.step) * 100;

    AB.msg(" &nbsp; y = (" + y.toString() + ") <br>" +
        " Bad steps: " + badsteps +
        " &nbsp; Good steps: " + goodsteps +
        " &nbsp; Score: " + score.toFixed(2) + "% ", 2);
}





AB.world.newRun = function () {
    AB.loadingScreen();

    AB.runReady = false;

    badsteps = 0;
    goodsteps = 0;


    if (show3d) {
        BOXHEIGHT = squaresize;
        ABWorld.init3d(startRadiusConst, maxRadiusConst, SKYCOLOR);
    }
    else {
        BOXHEIGHT = 1;
        ABWorld.init2d(startRadiusConst, maxRadiusConst, SKYCOLOR);
    }


    loadResources();		// aynch file loads		
    // calls initScene() when it returns 

    document.onkeydown = keyHandler;

};



AB.world.getState = function () {
    var x = [ai, aj, ei, ej];
    return (x);
};



AB.world.takeAction = function (a) {
    updateStatusBefore(a);			// show status line before moves 

    moveLogicalAgent(a);

    //   if ( ( AB.step % 2 ) == 0 )		// slow the enemy down to every nth step
    moveLogicalEnemy();


    if (badstep()) badsteps++;
    else goodsteps++;

    drawAgent();
    drawEnemy();
    updateStatusAfter();			// show status line after moves  


    if (agentBlocked())			// if agent blocked in, run over
    {
        AB.abortRun = true;
        goodsteps = 0;			// you score zero as far as database is concerned 			 
        musicPause();
        soundAlarm();
    } else if (AB.pauseOnAgentCapture && agentCaught()) {
        // RL: Adding new logic to abort when enemy has caught the agent, 
        // otherwise the enemy keeps following the agent on every move until it gets trapped
        AB.abortRun = true;
        AB.agentCaught = true;
        musicPause();
        soundAlarm();
    }

};


AB.world.endRun = function () {
    musicPause();

    // RL: Added logic to show message on agentCaught
    if (AB.abortRun && AB.agentCaught) AB.msg(" <br> <font color=orange> <B> Agent was Caught.</B> </font>   ", 3);
    else if (AB.abortRun) AB.msg(" <br> <font color=red> <B> Agent trapped. Final score zero. </B> </font>   ", 3);
    else AB.msg(" <br> <font color=green> <B> Run over. </B> </font>   ", 3);

    console.log({report: REPORT});
};


AB.world.getScore = function () {
    // only called at end - do not use AB.step because it may have just incremented past AB.maxSteps

    var s = (goodsteps / AB.maxSteps) * 100;   // float like 93.4372778 
    var x = Math.round(s * 100);                // 9344
    return (x / 100);                          // 93.44
};


// --- music and sound effects ----------------------------------------

var backmusic = AB.backgroundMusic(MUSIC_BACK);

function musicPlay() { backmusic.play(); }
function musicPause() { backmusic.pause(); }


function soundAlarm() {
    var alarm = new Audio(SOUND_ALARM);
    alarm.play();							// play once, no loop 
}