I've been following W3schools tutorial on creating a JavaScript game in a canvas https://www.w3schools.com/graphics/game_obstacles.asp
I've got to the stage where they add an obstacle in. Currently, it has collision detection which stops the game when it hits the wall. I am trying to figure out a way to treat it like a wall where the box could hit it and no longer move that direction and continue the game, making the wall work.
Heres what I've got so far:
https://jsfiddle.net/j9cy1mne/1/
<body onload="startGame()">
<script>
var myGamePiece;
var myObstacle;
var speed = 3;
function startGame() {
myGamePiece = new component(30, 30, "red", 10, 120);
myObstacle = new component(10, 200, "green", 300, 120);
myGameArea.start();
}
var myGameArea = {
canvas: document.createElement("canvas"),
start: function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
},
clear: function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
},
stop: function() {
clearInterval(this.interval);
}
}
function component(width, height, color, x, y) {
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.crashWith = function(otherobj) {
var myleft = this.x;
var myright = this.x + (this.width);
var mytop = this.y;
var mybottom = this.y + (this.height);
var otherleft = otherobj.x;
var otherright = otherobj.x + (otherobj.width);
var othertop = otherobj.y;
var otherbottom = otherobj.y + (otherobj.height);
var crash = true;
if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
crash = false;
}
return crash;
}
}
function updateGameArea() {
if (myGamePiece.crashWith(myObstacle)) {
console.log("crash");
} else {
myGameArea.clear();
myObstacle.update();
myGamePiece.x += myGamePiece.speedX;
myGamePiece.y += myGamePiece.speedY;
myGamePiece.update();
}
}
document.onkeydown = checkKeyD;
function checkKeyD(e) {
e = e || window.event;
if (e.keyCode == '38') {
// up arrow
myGamePiece.speedY = -speed;
} else if (e.keyCode == '40') {
// down arrow
myGamePiece.speedY = speed;
} else if (e.keyCode == '37') {
// left arrow
myGamePiece.speedX = -speed;
} else if (e.keyCode == '39') {
// right arrow
myGamePiece.speedX = speed;
}
}
document.onkeyup = clearmove;
function clearmove() {
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
}
</script>
</body>
I see that you have part of it finished. You just need to have the crash code in the if statement for moving the player right. This will run the code only when the player is pressing the right arrow.
else if (e.keyCode == '39') {
// right arrow
// add crash code here
myGamePiece.speedX = speed;
}
Your game loop only executes when there is no crash:
function updateGameArea() {
if (myGamePiece.crashWith(myObstacle)) {
console.log("crash");
} else {
myGameArea.clear();
myObstacle.update();
myGamePiece.x += myGamePiece.speedX;
myGamePiece.y += myGamePiece.speedY;
myGamePiece.update();
}
}
What you want to do is to set the myGamePiece.speedX and myGamePiece.speedX to 0 when a collision is detected. Something like:
function updateGameArea() {
myGameArea.clear();
myObstacle.update();
if (myGamePiece.crashWith(myObstacle)) {
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
}
myGamePiece.x += myGamePiece.speedX;
myGamePiece.y += myGamePiece.speedY;
myGamePiece.update();
}
Edit: You probably want to apply some code to "back up" when a collision is detected, so the pieces are no longer in a collided state
Related
I need to resize my spritesheet so it fits the correct dimensions of my game object. I have been looking around the internet and I found that this -ctx.drawImage(image, sx, sy, sWidth, sHeight, dx, dy, dWidth, dHeight);- is what i think i need to use. however, i do not know how or where to implement this in my code. i know how it works but i dont know where to put it or where in my code to put it. i use almost completely javascript
var myGamePiece;
var myObstacle;
var object1;
var objects;
var box;
function startGame() {
//creation of objects
wall = new component(30, 100, "black", 300, 200);
myGamePiece = new component(30, 30, "red", 240, 135);
myObstacle = new component(100, 100, "green", 200, 100);
object1 = new component(30, 30, "enemy.png", 340, 125, "image");
box = new component(30, 30, "box.png", 177, 145, "image");
myGameArea.start();
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.key = e.keyCode;
})
window.addEventListener('keyup', function (e) {
myGameArea.key = false;
})
},
clear : function() {
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
},
collide : function() {
object1.x += 1;
object1.y += 1;
},
//what to do when pushing box
boxleft : function() {
box.x -= 1;
x -= 1;
}
}
function component(width, height, color, x, y, type) {
this.type = type;
if (type == "image") {
this.image = new Image();
this.image.src = color;
}
this.sx = x;
this.sy = y;
this.swidth = width;
this.sheight = height;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
if (type == "image") {
ctx.drawImage(this.image,
this.x,
this.y,
this.width,
this.height
);
} else {
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
}
this.newPos = function() {
this.x += this.speedX;
this.y += this.speedY;
}
//code for gray square
this.crashWith = function(object1) {
var myleft = this.x;
var myright = this.x + (this.width);
var mytop = this.y;
var mybottom = this.y + (this.height);
var otherleft = object1.x;
var otherright = object1.x + (object1.width);
var othertop = object1.y;
var otherbottom = object1.y + (object1.height);
var crash = true;
if ((mybottom < othertop) ||
(mytop > otherbottom) ||
(myright < otherleft) ||
(myleft > otherright)) {
crash = false;
}
return crash;
}
//code to push box
this.pushboxWith = function(box) {
const myleft = this.x;
const myright = this.x + (this.width);
const mytop = this.y;
const mybottom = this.y + (this.height);
const boxleft = box.x-2;
const boxright = box.x + (box.width)+2;
const boxtop = box.y+2;
const boxbottom = box.y + (box.height)-2;
var pushboxleft = true;
var pushboxright = true;
//test if pushing box
if ((myleft < boxright) && (mybottom >= boxtop) && (mytop <= boxbottom) && (myleft > boxleft)) {
pushboxleft = true;
} else {
pushboxleft = false;
}
return pushboxleft;
}
}
function updateGameArea() {
if (myGamePiece.crashWith(object1)) {
myGameArea.collide();
} else if (myGamePiece.pushboxWith(box)) {
myGameArea.boxleft();
} else {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
//keyboard controls. moves everything but the player
if (myGameArea.key && myGameArea.key == 37) {
myObstacle.x += 2;
object1.x += 2;
box.x += 2;
wall.x += 2;
}
if (myGameArea.key && myGameArea.key == 39) {
myObstacle.x += -2;
object1.x += -2;
box.x += -2;
wall.x += -2;
}
if (myGameArea.key && myGameArea.key == 38) {
myObstacle.y += 2;
object1.y += 2;
box.y += 2;
wall.y += 2
}
if (myGameArea.key && myGameArea.key == 40) {
myObstacle.y += -2;
object1.y += -2;
box.y += -2;
wall.y += -2
}
//other square movement. disabled to isolate code.
/*
if (object1.x < myGamePiece.x) {
object1.x += 1;
}
if (object1.x > myGamePiece.x) {
object1.x += -1;
}
if (object1.y < myGamePiece.y) {
object1.y += 1;
}
if (object1.y > myGamePiece.y) {
object1.y += -1;
}
*/
/* object order: the object that is higher on the list
will be on top of objects lower on the list
*/
myObstacle.update();
myGamePiece.newPos();
myGamePiece.update();
wall.update();
object1.update();
box.update();
//end of list
}
}
i do use some html
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
border:1px solid #d3d3d3;
background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script src="main.js"></script>
</body>
</html>
if you need to test my code you can find it here- https://eeeegame-2.octopuscat.repl.co/
I am very new to coding. I am trying to make a game using java in notepad++. I cant seem to get it so that when the red square (player) hits the purple (TopEdge) the red square will not stop completely but also wont travel through the purple. Like a wall. Right now when the red square hits the purple, you cant move it anymore. I have tried almost everything i could find on the internet. Here is my code:
<!DOCTYPE html>
<html lang="en">
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<meta charset="utf-8">
<style>
canvas {
border:4px solid #000000;
background-color: #1FB026;
}
</style>
</head>
<body onload="startGame()">
<script>
var player;
var TopEdge;
function startGame() {
player = new component(30, 30, "red", 10, 120);
TopEdge = new component(10000, 300, "purple", 0, -200);
myGameArea.start();
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 1150;
this.canvas.height = 500;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas,
document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 10);
window.addEventListener('keydown', function (e) {
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
},
stop : function(){
clearInterval(this.interval);
}
}
function component(width, height, color, x, y) {
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.X += this.speedX;
this.Y += this.speedY;
let playerX = this.X + this.speedX;
let playerY = this.Y + this.speedY;
if (playerX >= 0 && this.width + playerX <= this.gamearea.canvas.width)
{
this.X = playerX;
}
if (playerY >= 0 && this.height + playerY <= this.gamearea.canvas.height)
{
this.Y = playerY;
}
}
this.crashWith = function(otherobj) {
var myleft = this.x;
var myright = this.x + (this.width);
var mytop = this.y;
var mybottom = this.y + (this.height);
var otherleft = otherobj.x;
var otherright = otherobj.x + (otherobj.width);
var othertop = otherobj.y;
var otherbottom = otherobj.y + (otherobj.height);
var crash = true;
if ((mybottom < othertop) ||
(mytop > otherbottom) ||
(myright < otherleft) ||
(myleft > otherright)) {
crash = false;
}
return crash;
}
}
function stopY() {
player.speedY = 0;
}
function updateGameArea() {
if (player.crashWith(TopEdge)) {
} else {
myGameArea.clear();
TopEdge.update();
player.x += player.speedX;
player.y += player.speedY;
player.update();
}
TopEdge.update();
player.speedX = 0;
player.speedY = 0;
if (myGameArea.keys && myGameArea.keys[65]) {player.speedX = -2.5; }
if (myGameArea.keys && myGameArea.keys[68]) {player.speedX = 2.5; }
if (myGameArea.keys && myGameArea.keys[87]) {player.speedY = -2.5; }
if (myGameArea.keys && myGameArea.keys[83]) {player.speedY = 2.5; }
player.newPos();
player.update();
}
</script>
</body>
</html>
The problem starts with your updateGameArea() function.
If your the player crashes with the TopEdge then you do nothing. Your creating a problem with your else-part over there. It will never reach the else like this, so nothing while change, so next time it still won't move and again it will not reach the else.....
How about removing the else part. Just check for everything all the time, but don't allow it to move up when it reached the TopEdge.
This should help.
function updateGameArea() {
// I'd prefer these calls at the end of the function block
// but right now your program would start kinda buggy then
myGameArea.clear();
player.newPos();
player.update();
TopEdge.update();
// In default state (nothing pressed) player shouldn't move up or down
player.speedX = 0;
player.speedY = 0;
// If the player does press a key set correct speed/direction
if (myGameArea.keys[65]) {player.speedX = -2.5; }
if (myGameArea.keys[68]) {player.speedX = 2.5; }
if (myGameArea.keys[87]) {player.speedY = -2.5; }
if (myGameArea.keys[83]) {player.speedY = 2.5; }
// Check if player reached the top
// If it did, then it shouldn't be able to climb any higher.
// So even if the player presses the up-button,
// the vertical speed should still not be aloud to change.
if (player.crashWith(TopEdge) && myGameArea.keys[87]) {
player.speedY = 0;
}
// Move the position of the player
player.x += player.speedX; //
player.y += player.speedY;
}
I am trying to create a basic platformer game, and I'm working on the gravity section. I am using some if myGameArea.keys statements to allow the player to move their character forwards and backwards, and up. I am using an accelerate function to stop gravity when the up key is pressed, but I can't make it start again when the key is lifted. I know how to implement the onkeyup function (onkeyup = function();) but I don't know how to add it to my code.
<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
border:1px solid #d3d3d3;
background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
var myGamePiece;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 10, 240);
}
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas,
document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keyup");
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y, type) {
this.type = type;
this.width = width;
this.height = height;
this.x = x;
this.y = y;
this.speedX = 0;
this.speedY = 0;
this.gravity = 0.05;
this.gravitySpeed = 0;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY + this.gravitySpeed;
this.hitBottom();
}
this.hitBottom = function() {
var rockbottom = myGameArea.canvas.height - this.height;
if (this.y > rockbottom) {
this.y = rockbottom;
}
}
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
myGamePiece.gravity = 0.1;
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedX = -2;
}
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedX = 2;
}
if (myGameArea.keys && myGameArea.keys[38]) {accelerate(-0.2)}
myGamePiece.newPos();
myGamePiece.update();
}
function accelerate(n) {
myGamePiece.gravity = n;
}
</script>
</body>
</html>
This is only a small portion of the code. If anyone would like the full amount, comment below to tell me, please. Thanks for your help!
Some issues:
In your keyup event handler, you have:
myGameArea.keys[e.keyCode] = (e.type == "keyup");
But this will set the property value to true. You want false, so just do:
myGameArea.keys[e.keyCode] = false;
(BTW, this error was not there in one of your previous question versions, where you had (e.type == "keydown").
You can also simply set to true in the keydown handler (but there was no error there).
Secondly, the gravitySpeed keeps increasing even when you hit the bottom. This will make that value incredible great, and the counter accelaration when pressing the up key will not have any visible effect, unless you wait long enough. Instead, reset `gravitySpeed here::
this.y = rockbottom;
this.gravitySpeed = 0; // <----
See it run:
var myGamePiece;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 10, 240);
}
var myGameArea = {
canvas: document.createElement("canvas"),
keys: [], // <--- just initialise here
start: function() {
window.focus();
this.canvas.width = 480;
this.canvas.height = 180;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas,
document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.keys[e.keyCode] = true; // <---
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = false; // <---
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y, type) {
this.type = type;
this.width = width;
this.height = height;
this.x = x;
this.y = y;
this.speedX = 0;
this.speedY = 0;
this.gravity = 0.05;
this.gravitySpeed = 0;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY + this.gravitySpeed;
this.hitBottom();
}
this.hitBottom = function() {
var rockbottom = myGameArea.canvas.height - this.height;
if (this.y > rockbottom) {
this.y = rockbottom;
this.gravitySpeed = 0; // <----
}
}
}
function updateGameArea() {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
myGamePiece.gravity = 0.1;
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedX = -2; }
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedX = 2; }
if (myGameArea.keys && myGameArea.keys[38]) {accelerate(-0.2)}
myGamePiece.newPos();
myGamePiece.update();
}
function accelerate(n) {
myGamePiece.gravity = n;
}
window.onload = startGame;
canvas {
border:1px solid #d3d3d3;
background-color: #f1f1f1;
}
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I am creating a platformer in javascript, and I am making a gravity sytem on it. What happens is that gravity is reduced when the player presses the up arrow key. The problem is that the user can press the up arrow multiple times and jump whilst already jumping. Any way to sort this out?
Here is my code:
<!DOCTYPE>
<html>
<head>
<style>
canvas {
border: 1px solid #000000;
background-color: rgb(0, 200, 200);
}
</style>
</head>
<body onload = "startGame()">
<canvas id="myCanvas" width="750" height="300">
<script>
var myGamePiece;
var floor;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 10, 230);
floor = new component(750, 10, "green", 0, 260);
}
var myGameArea = {
canvas : document.getElementById('myCanvas'),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y) {
this.gamearea = myGameArea;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
this.gravity = 0.05;
this.gravitySpeed = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY + this.gravitySpeed;
this.hitBottom();
}
this.hitBottom = function() {
var rockbottom = myGameArea.canvas.height - this.height - 10;
if (this.y > rockbottom) {
this.y = rockbottom;
this.gravitySpeed = 0;
}
}
}
function updateGameArea() {
myGameArea.clear();
floor.update();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
if (myGameArea.keys && myGameArea.keys[37]) {
myGamePiece.speedX = -2.5;
}
if (myGameArea.keys && myGameArea.keys[39]) {
myGamePiece.speedX = 2.5;
}
if (myGameArea.keys && myGameArea.keys[38]) {
accelerate(-0.2)
} else{
accelerate(0.1)
}
if (myGameArea.keys && myGameArea.keys[40]) {
myGamePiece.speedY = 2.5;
}
myGamePiece.newPos();
myGamePiece.update();
}
function accelerate(n) {
myGamePiece.gravity = n;
}
</script>
</canvas>
</body>
</html>
You only need to check myGamePiece.y >=230 before accelarting
I have changed only two things in your code and it works fine
if (myGameArea.keys && myGameArea.keys[40] && myGamePiece.y >= 230) last if block of your function updateGameArea()
Second Last if block of your updateGameArea()
if (myGameArea.keys && myGameArea.keys[38]) {
if(myGamePiece.y >= 230) accelerate(-0.2)
}
var myGamePiece;
var floor;
function startGame() {
myGameArea.start();
myGamePiece = new component(30, 30, "red", 10, 230);
floor = new component(750, 10, "green", 0, 260);
}
var myGameArea = {
canvas : document.getElementById('myCanvas'),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 20);
window.addEventListener('keydown', function (e) {
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
},
clear : function(){
this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
}
}
function component(width, height, color, x, y) {
this.gamearea = myGameArea;
this.width = width;
this.height = height;
this.speedX = 0;
this.speedY = 0;
this.gravity = 0.05;
this.gravitySpeed = 0;
this.x = x;
this.y = y;
this.update = function() {
ctx = myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function() {
this.gravitySpeed += this.gravity;
this.x += this.speedX;
this.y += this.speedY + this.gravitySpeed;
this.hitBottom();
}
this.hitBottom = function() {
var rockbottom = myGameArea.canvas.height - this.height - 10;
if (this.y > rockbottom) {
this.y = rockbottom;
this.gravitySpeed = 0;
}
}
}
function updateGameArea() {
myGameArea.clear();
floor.update();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
if (myGameArea.keys && myGameArea.keys[37]) {
myGamePiece.speedX = -2.5;
}
if (myGameArea.keys && myGameArea.keys[39]) {
myGamePiece.speedX = 2.5;
}
if (myGameArea.keys && myGameArea.keys[38]) {
if(myGamePiece.y >= 230) accelerate(-0.2)
} else{
accelerate(0.1)
}
if (myGameArea.keys && myGameArea.keys[40] && myGamePiece.y >= 230) {
myGamePiece.speedY = 2.5;
}
myGamePiece.newPos();
myGamePiece.update();
}
function accelerate(n) {
myGamePiece.gravity = n;
}
<body onload = "startGame()">
<canvas id="myCanvas" width="750" height="300">
Hope it helps
The main object keeps firing bullets and it looks like a lazer. I don't know how to make it fire one bullet at a press of a key. Do I need to use intervals?
var gameBullet=[];
var i=0;
//Starts game
function startGame() {
myGameArea.start();
myGamePiece= new component(20,20,"red",10,120);
}
//Creates canvas , events and how many times per sec should the object redraw
var myGameArea = {
canvas : document.createElement("canvas"),
start : function() {
this.canvas.width = 480;
this.canvas.height = 270;
this.context = this.canvas.getContext("2d");
document.body.insertBefore(this.canvas, document.body.childNodes[0]);
this.interval = setInterval(updateGameArea, 1);
window.addEventListener('keydown', function (e) {
myGameArea.keys = (myGameArea.keys || []);
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('keyup', function (e) {
myGameArea.keys[e.keyCode] = (e.type == "keydown");
})
window.addEventListener('space',function(e){
myGameArea.keys[e.keyCode] = (e.type == "space");
})
},
clear: function(){
this.context.clearRect(0,0,this.canvas.width,this.canvas.height);
}
}
//Bullet constructor
function bullet(width,height,color,x,y){
this.gamearea=myGameArea;
this.width=width;
this.height=height;
this.speedX=5;
this.x=x;
this.y=y;
this.update = function(){
ctx=myGameArea.context;
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos = function(){
this.x+=this.speedX;
this.hitBorder();
}
this.hitBorder = function() {
var right = myGameArea.canvas.width - this.width;
if (this.x > right) {
this.x = right;
}
}
}
//Main Object constructor
function component(width,height,color,x,y){
this.gamearea=myGameArea;
var imageObj = new Image();
this.width=width;
this.height=height;
this.speedX=0;
this.speedY=0;
this.x=x;
this.y=y;
this.update= function(){
ctx=myGameArea.context;
/* ctx.drawImage(imageObj,this.x,this.y, this.width, this.height);
imageObj.src = 'stalin.png';
*/
ctx.fillStyle = color;
ctx.fillRect(this.x, this.y, this.width, this.height);
}
this.newPos= function(){
this.x+=this.speedX;
this.y+=this.speedY;
this.hitBorder();
}
this.hitBorder = function() {
var down = myGameArea.canvas.height - this.height;
if (this.y > down) {
this.y = down;
}
if (this.y < 0) {
this.y = 0;
}
var right = myGameArea.canvas.width - this.width;
if (this.x > right) {
this.x = right;
}
if (this.x < 0) {
this.x = 0;
}
}
}
I think here is the problem. I need to add something in the loop, but I don't know what.
//Updates game
function updateGameArea() {
myGameArea.clear();
myGamePiece.speedX = 0;
myGamePiece.speedY = 0;
if (myGameArea.keys && myGameArea.keys[37]) {myGamePiece.speedX = -1; }
if (myGameArea.keys && myGameArea.keys[39]) {myGamePiece.speedX = 1; }
if (myGameArea.keys && myGameArea.keys[38]) {myGamePiece.speedY = -1; }
if (myGameArea.keys && myGameArea.keys[40]) {myGamePiece.speedY = 1; }
if (myGameArea.keys && myGameArea.keys[32])
{
gameBullet[i]=new bullet(5,5,"red",myGamePiece.x,myGamePiece.y);
i=i+1;
}
myGamePiece.newPos();
myGamePiece.update();
for( i=0;i<gameBullet.length;i+=1){
gameBullet[i].newPos();
gameBullet[i].update();
}
}
startGame();
you can use setinterval() in place of for loop
setinterval(yourcode,timespan);