# Calculating dynamic light and shadows in tile based roguelike games – part 4: a first real world example

I wanted to try a real world example of my dynamic light and shadows in tile based roguelike games, so let’s make a small recap then I am diving into the code: In first step I introduced Bresenham algorithm to draw a line between two points in a tile based environment. In step 2 with the same concept I showed you how to draw a circle in a tile based environment. In step 3 I connected all tiles along the circumference with the player using Bresenham line, stopping the line if it hits a wall. Today I am showing you a little example in a randomly generated dungeon. The code to generate the dungeon is taken from here and although it does not generate the best dungeons ever, it works so why not?
Drag the player – the green dot – inside the maze and see the light effect. To optimize a bit the code I added a `visited` array to keep track of tiles I already visited to avoid placing unnecessary tiles. More optimization and some performance statistics will be available next week, meanwhile have a look at the source code:
```var game;
var tileSize = 12;

game = new Phaser.Game(768, 768, Phaser.AUTO, "");
game.state.start("PlayGame");
}

var playGame = function(game){};

playGame.prototype = {
},
create: function(){
for(var i = 0; i < Dungeon.map_size; i++){
for(var j = 0; j < Dungeon.map_size; j++){
var tile = Dungeon.map[j][i];
if(tile == 0){
var wall = game.add.sprite(i * tileSize, j * tileSize, "tile");
wall.tint = 0x222222;
}
if(tile == 2){
var wall = game.add.sprite(i * tileSize, j * tileSize, "tile");
wall.tint = 0x555555;
}
}
}
var startCol = game.rnd.between(0, Dungeon.map_size - 1);
var startRow = game.rnd.between(0, Dungeon.map_size - 1);
this.playerPosition = game.add.sprite(startCol * tileSize, startRow * tileSize, "tile");
this.playerPosition.tint = 0x00ff00;
this.playerPosition.alpha = 0.5;
this.playerPosition.inputEnabled = true;
this.playerPosition.input.enableDrag();
this.playerPosition.input.boundsRect = new Phaser.Rectangle(0, 0, game.width, game.height);
this.playerPosition.input.enableSnap(tileSize, tileSize, true, true);

},
update: function(){
this.visited = [];
this.visited.length = 0;
this.lineGroup.removeAll(true);
this.drawCircle(this.playerPosition.x / tileSize, this.playerPosition.y / tileSize, sightRadius);
},
drawBresenham: function(x0, y0, x1, y1){
var saveX0 = x0;
var saveY0 = y0;
var dx = Math.abs(x1 - x0);
var sx = -1;
if(x0 < x1){
var sx = 1
}
var dy = Math.abs(y1 - y0);
var sy = -1;
if(y0 < y1){
var sy = 1;
}
var err = -dy / 2;
if(dx > dy){
err = dx / 2;
}
do{
var dist = this.distance(saveX0, saveY0, x0, y0);
if(x0 < 0 || y0 < 0 || x0 >= Dungeon.map_size || y0 >= Dungeon.map_size || Dungeon.map[y0][x0] != 1 || dist > sightRadius / 2){
break;
}
if(this.visited.indexOf(x0 + "," + y0) == -1){
var tile = game.add.sprite(x0 * tileSize, y0 * tileSize, "tile");
tile.tint = 0xffff00;
tile.alpha = 1 - dist / (sightRadius / 2);
this.visited.push(x0 + "," + y0);
}
var e2 = err;
if(e2 > -dx){
err -= dy;
x0 += sx;
}
if(e2 < dy){
err += dx;
y0 += sy;
}
} while(x0 != x1 || y0 != y1)
},
var y = 0;
var err = 2 - 2 * radius;
do {
this.drawBresenham(this.playerPosition.x / tileSize, this.playerPosition.y / tileSize, (x0 - x), (y0 + y));
this.drawBresenham(this.playerPosition.x / tileSize, this.playerPosition.y / tileSize, (x0 - y), (y0 - x));
this.drawBresenham(this.playerPosition.x / tileSize, this.playerPosition.y / tileSize, (x0 + x), (y0 - y));
this.drawBresenham(this.playerPosition.x / tileSize, this.playerPosition.y / tileSize, (x0 + y), (y0 + x));
y++;
err += y * 2 + 1;
}
if (radius > x || err > y){
x++;
err += x * 2 + 1;
}
} while (x < 0);
},
distance: function(x0, y0, x1, y1){
return Math.sqrt((x0-x1)*(x0-x1)+(y0-y1)*(y0-y1))
}
}

var Dungeon = {
map: null,
map_size: 64,
rooms: [],
Generate: function () {
this.map = [];
for (var x = 0; x < this.map_size; x++) {
this.map[x] = [];
for (var y = 0; y < this.map_size; y++) {
this.map[x][y] = 0;
}
}

var room_count = Helpers.GetRandom(10, 20);
var min_size = 5;
var max_size = 15;

for (var i = 0; i < room_count; i++) {
var room = {};

room.x = Helpers.GetRandom(1, this.map_size - max_size - 1);
room.y = Helpers.GetRandom(1, this.map_size - max_size - 1);
room.w = Helpers.GetRandom(min_size, max_size);
room.h = Helpers.GetRandom(min_size, max_size);

if (this.DoesCollide(room)) {
i--;
continue;
}
room.w--;
room.h--;

this.rooms.push(room);
}

this.SquashRooms();

for (i = 0; i < room_count; i++) {
var roomA = this.rooms[i];
var roomB = this.FindClosestRoom(roomA);

pointA = {
x: Helpers.GetRandom(roomA.x, roomA.x + roomA.w),
y: Helpers.GetRandom(roomA.y, roomA.y + roomA.h)
};
pointB = {
x: Helpers.GetRandom(roomB.x, roomB.x + roomB.w),
y: Helpers.GetRandom(roomB.y, roomB.y + roomB.h)
};

while ((pointB.x != pointA.x) || (pointB.y != pointA.y)) {
if (pointB.x != pointA.x) {
if (pointB.x > pointA.x) pointB.x--;
else pointB.x++;
} else if (pointB.y != pointA.y) {
if (pointB.y > pointA.y) pointB.y--;
else pointB.y++;
}

this.map[pointB.x][pointB.y] = 1;
}
}

for (i = 0; i < room_count; i++) {
var room = this.rooms[i];
for (var x = room.x; x < room.x + room.w; x++) {
for (var y = room.y; y < room.y + room.h; y++) {
this.map[x][y] = 1;
}
}
}

for (var x = 0; x < this.map_size; x++) {
for (var y = 0; y < this.map_size; y++) {
if (this.map[x][y] == 1) {
for (var xx = x - 1; xx <= x + 1; xx++) {
for (var yy = y - 1; yy <= y + 1; yy++) {
if (this.map[xx][yy] == 0) this.map[xx][yy] = 2;
}
}
}
}
}
},
FindClosestRoom: function (room) {
var mid = {
x: room.x + (room.w / 2),
y: room.y + (room.h / 2)
};
var closest = null;
var closest_distance = 1000;
for (var i = 0; i < this.rooms.length; i++) {
var check = this.rooms[i];
if (check == room) continue;
var check_mid = {
x: check.x + (check.w / 2),
y: check.y + (check.h / 2)
};
var distance = Math.min(Math.abs(mid.x - check_mid.x) - (room.w / 2) - (check.w / 2), Math.abs(mid.y - check_mid.y) - (room.h / 2) - (check.h / 2));
if (distance < closest_distance) {
closest_distance = distance;
closest = check;
}
}
return closest;
},
SquashRooms: function () {
for (var i = 0; i < 10; i++) {
for (var j = 0; j < this.rooms.length; j++) {
var room = this.rooms[j];
while (true) {
var old_position = {
x: room.x,
y: room.y
};
if (room.x > 1) room.x--;
if (room.y > 1) room.y--;
if ((room.x == 1) && (room.y == 1)) break;
if (this.DoesCollide(room, j)) {
room.x = old_position.x;
room.y = old_position.y;
break;
}
}
}
}
},
DoesCollide: function (room, ignore) {
for (var i = 0; i < this.rooms.length; i++) {
if (i == ignore) continue;
var check = this.rooms[i];
if (!((room.x + room.w < check.x) || (room.x > check.x + check.w) || (room.y + room.h < check.y) || (room.y > check.y + check.h))) return true;
}

return false;
}
}

var Helpers = {
GetRandom: function (low, high) {
return~~ (Math.random() * (high - low)) + low;
}
};

Dungeon.Generate();
```
Remember roguelike games are turn based games so performance is not a top feature, anyway I will show you some full stats next week, meanwhile download the source code of this experiment.
215 GAME PROTOTYPES EXPLAINED WITH SOURCE CODE
// 1+2=3
// 10000000
// 2 Cars
// 2048
// Avoider
// Ballz
// Block it
// Blockage
// Bloons
// Boids
// Bombuzal
// Breakout
// Bricks
// Columns
// CubesOut
// Dots
// DROP'd
// Dudeski
// Eskiv
// Filler
// Fling
// Globe
// HookPod
// Hundreds
// InkTd
// Iromeku
// Lumines
// Magick
// MagOrMin
// Maze
// Memdot
// Nano War
// Nodes
// o:anquan
// Ononmin
// Pacco
// Phyballs
// Platform
// Poker
// Pool
// Poux
// Pudi
// qomp
// Racing
// Renju
// SameGame
// Security
// Sling
// Slingy
// Sokoban
// Splitter
// Sproing
// Stack
// Stairs
// Stringy
// Sudoku
// Tetris
// Threes
// Toony
// Turn
// TwinSpin
// vvvvvv
// Wordle
// Worms
// Yanga
// Zhed
// zNumbers