Talking about Game development, HTML5, Javascript and Phaser.
One of the most interesting features introduce in platform games is the ability to jump on enemies and maybe squashing them to death. I am not sure which game was the first to introduce this feature, I would say some chapter in the Mario Bros series, although I am pretty sure in the very first game you couldn’t squash enemies. Anyway, we are going to see how we can develop this feature in our HTML5 games using Phaser and ARCADE physics. Let’s have a look at the result: Our hero is the green character, while the red one is the enemy. Both characters run and change direction once they hit the wall, and you can make green character jump by clicking/tapping on the canvas. If red character hits green character, the game restarts. Try to jump over the red character and you will bounce over it. This is made by checking the side of the collision between red and green character. We can say the green character is jumping over the red character when the red character collides on its TOP side while the green character collides on its BOTTOM side. Have a look at the completely commented source code:
var game;
var gameOptions = {
// width of the game, in pixels
gameWidth: 640,
// height of the game, in pixels
gameHeight: 192,
// background color
bgColor: 0x444444,
// player gravity
playerGravity: 1900,
// player horizontal speed
playerSpeed: 200,
// player force
playerJump: 400,
// enemy horizontal speed
enemySpeed: 150
}
window.onload = function() {
game = new Phaser.Game(gameOptions.gameWidth, gameOptions.gameHeight);
game.state.add("PreloadGame", preloadGame);
game.state.add("PlayGame", playGame);
game.state.start("PreloadGame");
}
var preloadGame = function(game){}
preloadGame.prototype = {
preload: function(){
game.stage.backgroundColor = gameOptions.bgColor;
game.scale.scaleMode = Phaser.ScaleManager.SHOW_ALL;
game.scale.pageAlignHorizontally = true;
game.scale.pageAlignVertically = true;
game.stage.disableVisibilityChange = true;
// loading level tilemap
game.load.tilemap("level", 'level.json', null, Phaser.Tilemap.TILED_JSON);
// loading game assets
game.load.image("tile", "tile.png");
game.load.image("hero", "hero.png");
game.load.image("enemy", "enemy.png");
},
create: function(){
game.state.start("PlayGame");
}
}
var playGame = function(game){}
playGame.prototype = {
create: function(){
// starting ARCADE physics
game.physics.startSystem(Phaser.Physics.ARCADE);
// creatin of "level" tilemap
this.map = game.add.tilemap("level");
// adding tiles (actually one tile) to tilemap
this.map.addTilesetImage("tileset01", "tile");
// tile 1 (the black tile) has the collision enabled
this.map.setCollision(1);
// which layer should we render? That's right, "layer01"
this.layer = this.map.createLayer("layer01");
// adding the hero sprite
this.hero = game.add.sprite(game.width / 2, 152, "hero");
// setting hero anchor point
this.hero.anchor.set(0.5);
// enabling ARCADE physics for the enemy
game.physics.enable(this.hero, Phaser.Physics.ARCADE);
// setting hero gravity
this.hero.body.gravity.y = gameOptions.playerGravity;
// setting hero horizontal speed
this.hero.body.velocity.x = gameOptions.playerSpeed;
// adding the enemy sprite
this.enemy = game.add.sprite(game.width / 4, 152, "enemy");
// setting enemy anchor point
this.enemy.anchor.set(0.5);
// enabling ARCADE physics for the enemy
game.physics.enable(this.enemy, Phaser.Physics.ARCADE);
// setting enemy horizontal speed
this.enemy.body.velocity.x = gameOptions.enemySpeed;
// the hero can jump
this.canJump = true;
// waiting for player input
game.input.onDown.add(this.handleJump, this);
},
handleJump: function(){
// the hero can jump when:
// canJump is true AND the hero is on the ground (blocked.down)
if((this.canJump && this.hero.body.blocked.down)){
// applying jump force
this.hero.body.velocity.y = -gameOptions.playerJump;
// hero can't jump anymore
this.canJump = false;
}
},
update: function(){
// handling collision between the hero and the tiles
game.physics.arcade.collide(this.hero, this.layer, function(hero, layer){
// hero on the ground
if(hero.body.blocked.down){
// hero can jump
this.canJump = true;
}
// hero on the ground and touching a wall on the right
if(this.hero.body.blocked.right && this.hero.body.blocked.down){
// horizontal flipping hero sprite
this.hero.scale.x = -1;
}
// same concept applies to the left
if(this.hero.body.blocked.left && this.hero.body.blocked.down){
this.hero.scale.x = 1;
}
// adjusting hero speed according to the direction it's moving
this.hero.body.velocity.x = gameOptions.playerSpeed * this.hero.scale.x;
}, null, this);
// handling collision between the enemy and the tiles
game.physics.arcade.collide(this.enemy, this.layer, function(hero, layer){
// enemy touching a wall on the right
if(this.enemy.body.blocked.right){
// horizontal flipping enemy sprite
this.enemy.scale.x = -1;
}
// same concept applies to the left
if(this.enemy.body.blocked.left){
this.enemy.scale.x = 1;
}
// adjusting enemy speed according to the direction it's moving
this.enemy.body.velocity.x = gameOptions.enemySpeed * this.enemy.scale.x;
}, null, this);
// handling collision between enemy and hero
game.physics.arcade.collide(this.hero, this.enemy, function(hero, enemy){
// hero is stomping the enemy if:
// hero is touching DOWN
// enemy is touching UP
if(enemy.body.touching.up && hero.body.touching.down){
// in this case just jump again
this.hero.body.velocity.y = -gameOptions.playerJump;
}
else{
// any other way to collide on an enemy will restart the game
game.state.start("PlayGame");
}
}, null, this);
}
}
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