Code viewer for World: A Game of Prey and Predator
// Sanchit Shreepraksh Akhauri 20210205

// Cloned by Sanchit Akhauri on 20 Nov 2020 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 = 200;

// 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 = 50;

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



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

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

const diagonal = true; //  true;                      // Sanchit :- Allows diagonal run of enemy

const TEXTURE_WALL = '/uploads/sanchit08/forest.jpg';
const TEXTURE_MAZE = '/uploads/sanchit08/Tree_snap.jpg';
const TEXTURE_AGENT = '/uploads/sanchit08/Deer.jpg';
const TEXTURE_ENEMY = '/uploads/sanchit08/Tiger.jpg';

const MUSIC_BACK = '/uploads/sanchit08/Forest.mp3';
const SOUND_ALARM = '/uploads/sanchit08/Tiger.mp3';

const gridsize = 50;	// 50					// number of squares along side of world	   

const NOBOXES = Math.trunc((gridsize * gridsize) / 3);  // 3
// 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

var targeti = 1;                                    // Sanchit : -target i co-ordinate for smart agent
var targetj = 1;                                    // Sanchit : -target j co-ordinate for smart agent
var targetIndex = 0;                                // Sanchit : current index of targetValue
var targetValue = new Array(4);                     // Sanchit : Stored value of four random edges co-ordinates.

//--- skybox: -------------------------------

const SKYBOX_ARRAY = [
    "/uploads/sanchit08/snap1_resize.png",
    "/uploads/sanchit08/snap2_resize.png",
    "/uploads/sanchit08/sky_resize.png",
    "/uploads/sanchit08/grass_snap.png",
    "/uploads/sanchit08/snap3_resize.png",
    "/uploads/sanchit08/snap4_resize.png"
];



// ===================================================================================================================
// === 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;
const TARGET = 3; // Sanchit :- 4 targets for the smart agent is defined as 3 in the GRID variable





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 theagent, theenemy;

var wall_texture, agent_texture, enemy_texture, maze_texture;


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

var badsteps;
var goodsteps;

// Sanchit : - Store co-ordinates of agent and enemy at every step
var source;
var destination;

// Sanchit : -Stores position of co-ordinates which are closed
var closedList = new Array(gridsize);

// Sanchit : - Stores position of co-ordinates which are open to access and not in closed list.
var openList = {};

function pair(i, j) {  // Sanchit : -  Stores x and y coordinates
    this.i = i;
    this.j = j;
}

function Details(f, g, h, parent_i, parent_j) { // Sanchit : -  Stores evaluation function value of each step and parent co-ordinates
    this.f = f;
    this.g = g;
    this.h = h;
    this.parent_i = parent_i;
    this.parent_j = parent_j;
}

function pPair(f, i, j) { // Sanchit : -  Store f(n) value and co-ordinates of each square
    this.f = f;
    this.set = new pair(i, j);
}

// Sanchit : -  A Utility Function to check whether given cell (row, col) 
// is a valid cell or not. 
function isValid(row, col) {
    // Returns true if row number and column number 
    // is in range 
    return (row >= 0) && (row < gridsize) &&
        (col >= 0) && (col < gridsize);
}

// Sanchit : -  A Utility Function to check whether destination cell has 
// been reached or not 
function isDestination(row, col, destination) {
    if (row == destination.i && col == destination.j)
        return (true);
    else
        return (false);
}

// Sanchit : - A Utility Function to trace the path from the source 
// to destination 

var finalpath = [];
function tracePath(cellDetails, dest) {
    finalpath = [];
    var row = dest.i;
    var col = dest.j;

    var Path = [];

    //Stores the co-orinates of parents from distination to source in path variable 
    while (!(cellDetails[row][col].parent_i == row
        && cellDetails[row][col].parent_j == col)) {
        Path.push(new pair(row, col));
        var temp_row = cellDetails[row][col].parent_i;
        var temp_col = cellDetails[row][col].parent_j;
        row = temp_row;
        col = temp_col;
    }

    Path.push(new pair(row, col));

    // Stores values from path variable to finalpath variable in the order from enemy to agent
    while (Path.length > 0)
        finalpath.push(Path.pop());
}

// Sanchit : - Heuristic evaluation function 
function heuristic(i, j) {

    // return euclidean distance
    axisj_distance = aj - j;
    axisi_distance = ai - i;
    var result = Math.sqrt(Math.pow(axisi_distance, 2) + Math.pow(axisj_distance, 2));
    return result;
}

// Sanchit : - Check if the co-ordinate is not bloxed by boundary and obstacles.
function isUnBlocked(i, j) {
    // Returns true if the cell is not blocked else false 
    if (GRID[i][j] == GRID_WALL) return false;	 
    if (GRID[i][j] == GRID_MAZE) return false;
    if (GRID[i][j] == TARGET) return false;

    return true;
}

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();
    });

}


function asynchFinished()		 // all file loads returned 
{
    if (wall_texture && agent_texture && enemy_texture && maze_texture) return true;
    else return false;
}




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


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] == GRID_WALL) return true;		// fixed objects	 
    if (GRID[i][j] == GRID_MAZE) return true;
    if (GRID[i][j] == TARGET) 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) {
    var v = new THREE.Vector3();

    v.y = 0;
    v.x = (i * squaresize) - (MAXPOS / 2);
    v.z = (j * squaresize) - (MAXPOS / 2);

    return v;
}


function setupLine(finalPath) {   // Sanchit : - This function draws the A* path from the enemy to the agent with blue line every time enemy takes a step. 
    const material = new THREE.LineBasicMaterial( { color: 0xFF0000 } );
    
    const points = [];
    
    for(var i=1;i<finalPath.length;i++)
        points.push( translate(finalPath[i].i, finalPath[i].j));
    
    const geometry = new THREE.BufferGeometry().setFromPoints( points );
    const line = new THREE.Line( geometry, material );
    ABWorld.scene.add(line);
    setTimeout(() => {
        geometry.dispose();
        material.dispose();
        ABWorld.scene.remove(line);
        },AB.clockTick);
}

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

    // set up GRID, closedList, openList as 2D array

    for (i = 0; i < gridsize; i++) {
        closedList[i] = new Array(gridsize);
        GRID[i] = new Array(gridsize);
    }

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

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

    // set up maze 

    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] = 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);
    }

    // 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();

    if(agentIntelligent)        // Sanchit : - Setup 4 edges value when the agent is smart
        updateTargetValue();  // Sanchit : - update target value for the agent

    // Sanchit : -Store co-ordinates of enemy and agent
    source = new pair(ei, ej);
    destination = new pair(ai, aj);


    // 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
    });

}

function updateTargetValue(){   // Sanchit : - updates target value for the agent by calling checkEmptySquare function.
    checkEmptySquare(1, Math.abs((gridsize - 2)/2),1, Math.abs((gridsize - 2)/2),0);
    checkEmptySquare(1, Math.abs((gridsize - 2)/2),Math.abs((gridsize - 2)/2), gridsize - 2,1);
    checkEmptySquare(Math.abs((gridsize - 2)/2), gridsize - 2,1, Math.abs((gridsize - 2)/2),2);
    checkEmptySquare(Math.abs((gridsize - 2)/2),gridsize-2,Math.abs((gridsize - 2)/2),gridsize-2,3);     
}
function checkEmptySquare(a,b,c,d,index){ // Sanchit : - Finds the available 4 co-ordinates from the four parts of the maze randomnly.
    var i =0;
    var j =0;
    do {
        i = AB.randomIntAtoB(a,b);
        j = AB.randomIntAtoB(c,d);
    }
    while (occupied(i, j)); 
    targetValue[index] = new pair(i,j);
    GRID[i][j] = TARGET;
}


// --- 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)
}




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

function updateOpenList(i, j, open_i, open_j, cellDetails) { // Sanchit : - this function updates the value of successor in openList

    // To store the 'g', 'h' and 'f' of the 8 successors 
    var gNew, hNew, fNew;
    var foundDest =false; // Flag to inform if the destination is found

    if (isValid(i, j)) {
        // If the destination cell is the same as the 
        // current successor 
        if (isDestination(i, j, destination)) {
            // Set the Parent of the destination cell 
            cellDetails[i][j].parent_i = open_i;
            cellDetails[i][j].parent_j = open_j;
            tracePath(cellDetails, destination);
            foundDest = true;
        }
        // If the successor is already on the closed 
        // list or if it is blocked, then ignore it. 
        // Else do the following 
        else if (closedList[i][j] == false &&
            isUnBlocked(i, j) == true) {
            gNew = cellDetails[open_i][open_j].g + 1.0;
            hNew = heuristic(i, j);
            fNew = gNew + hNew;

            if (cellDetails[i][j].f == Number.MAX_VALUE ||
                cellDetails[i][j].f > fNew) {
                openList[i + " " + j] = new pPair(fNew, i, j);

                // Update the details of this cell 
                cellDetails[i][j].f = fNew;
                cellDetails[i][j].g = gNew;
                cellDetails[i][j].h = hNew;
                cellDetails[i][j].parent_i = open_i;
                cellDetails[i][j].parent_j = open_j;
            }
        }
    }
    return foundDest;
}

function moveLogicalEnemy() {  // Sanchit : - This function uses A* algorithm to provide the next possible optimal distance movement for the enemy
    // Store co-ordinates of enemy
    source.i = ei;
    source.j = ej;

    // Stores position of co-ordinates which are closed
    closedList = Array.from({ length: gridsize }, () => Array.from({ length: gridsize }, () => false));

    //Store details of each square
    var cellDetails = new Array(gridsize);
    cellDetails = Array.from({ length: gridsize }, () => new Array(gridsize));
    cellDetails = Array.from({ length: gridsize }, () => Array.from({ length: gridsize }, () =>
        new Details(Number.MAX_VALUE, Number.MAX_VALUE, Number.MAX_VALUE, -1, -1)));

    //Update cellDetails value of enemy starting point
    var i = source.i;
    var j = source.j;
    cellDetails[i][j].f = 0.0;
    cellDetails[i][j].g = 0.0;
    cellDetails[i][j].h = 0.0;
    cellDetails[i][j].parent_i = i;
    cellDetails[i][j].parent_j = j;

    //Store f(n) and co-ordinates value in openList
    openList = {};
    openList[i + " " + j] = (new pPair(0.0, i, j));

    while (Object.keys(openList).length > 0) {

        //Pop the first value in openList
        var firstKey = Object.keys(openList)[0];
        var p = openList[firstKey];
        delete openList[firstKey];
     
        // Add this vertex to the closed list 
        open_i = p.set.i;
        open_j = p.set.j;
        closedList[open_i][open_j] = true;

        // Update openList value with successor co-ordinates which are valid
        if (updateOpenList(open_i + 1, open_j, open_i, open_j, cellDetails)) break;
        if (updateOpenList(open_i, open_j + 1, open_i, open_j, cellDetails)) break;
        if (updateOpenList(open_i - 1, open_j, open_i, open_j, cellDetails)) break;
        if (updateOpenList(open_i, open_j - 1, open_i, open_j, cellDetails)) break;
        if(diagonal)
        {
            if (updateOpenList(open_i + 1, open_j - 1, open_i, open_j, cellDetails)) break;
            if (updateOpenList(open_i + 1, open_j + 1, open_i, open_j, cellDetails)) break;
            if (updateOpenList(open_i - 1, open_j + 1, open_i, open_j, cellDetails)) break;
            if (updateOpenList(open_i - 1, open_j - 1, open_i, open_j, cellDetails)) break;
        }
    }

    if (finalpath.length > 2) {         // If finalpath's length is greater than 2 then the value in 1 index contains the next step.
        var bestPositionEnemy = finalpath[1];
        ei = bestPositionEnemy.i;
        ej = bestPositionEnemy.j
    }
    else if (finalpath.length == 0) {   // If final path is zero then no possible path is possible from the enemy to agent
        AB.abortRun = true;
        musicPause();
        AB.msg(" Tiger unable to find the deer");
    }
    else {              // If the enemy is near the agent in diaginal posiion then it is better to move to valid horizontal 
                        //or perpendicular position as the chances to trapping the agent increases.
        
        if ((ei + 1 == ai && ej + 1 == aj) || (ei - 1 == ai && ej - 1 == aj) || (ei + 1 == ai && ej - 1 == aj) || (ei - 1 == ai && ej + 1 == aj)) {
            if (ei + 1 == ai && !occupied(ei + 1, ej))
                ei = ei + 1;
            if (ei - 1 == ai && !occupied(ei - 1, ej))
                ei = ei - 1;
            if (ej + 1 == aj && !occupied(ei, ej + 1))
                ej = ej + 1;
            if (ej - 1 == aj && !occupied(ei, ej - 1))
                ej = ej - 1;
        }
    }
    
    setupLine(finalpath);  // Draw A* alogorithm suggested path on the screen
}


function moveLogicalAgent(a)			// this is called by the infrastructure that gets action a from the Mind 
{
    // Store co-ordinates of agent
    destination.i = ai;
    destination.j = aj;

    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 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);
};

function changeTargetValue(){ // Sanchit : - returns the next co-ordinate value from targetValue
    targetIndex = (targetIndex +1) % 4;
    var temp = targetValue[targetIndex];
    targeti = temp.i;
    targetj = temp.j;
}

AB.world.takeAction = function ( a )
{
    // Sanchit :- Change targeti and targej valuw when no. of steps by smart agent is gridsize or when 
    //distance between agent and target is <= gridsize/4 
  if(agentIntelligent && (AB.step % (gridsize) == 0 || ((Math.abs(ai - targeti) <= gridsize/4) && (Math.abs(aj - targetj) <= gridsize/4))))
    changeTargetValue()
  
    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();
    }

};



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


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 
}