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script.js
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script.js
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// Const
const rows = 20;
const cols = 20;
const blockSize = 25;
const supportsTouch = ('ontouchstart' in window) || (navigator.maxTouchPoints > 0) || (navigator.msMaxTouchPoints > 0);
// Board
let board;
let context;
let gameOver = false;
// Snake head
let snakeX = blockSize * 5;
let snakeY = blockSize * 5;
let velocityX = 0;
let velocityY = 0;
let snakeBody = [];
// Food
let foodX;
let foodY;
// Touch
let xDown = null;
let yDown = null;
// Functions
const update = () => {
if (gameOver) return;
context.fillStyle = "black";
context.fillRect(0, 0, board.width, board.height);
context.fillStyle = "red";
context.fillRect(foodX, foodY, blockSize, blockSize);
if (snakeX === foodX && snakeY === foodY) {
snakeBody.push([foodX, foodY]);
placeFood();
}
for (let i = snakeBody.length-1; i > 0; i--) snakeBody[i] = snakeBody[i-1];
if (snakeBody.length) snakeBody[0] = [snakeX, snakeY];
context.fillStyle = "lime";
snakeX += velocityX * blockSize;
snakeY += velocityY * blockSize;
context.fillRect(snakeX, snakeY, blockSize, blockSize);
for (let i = 0; i < snakeBody.length; i++) context.fillRect(snakeBody[i][0], snakeBody[i][1], blockSize, blockSize);
// Game over conditions
if (snakeX < 0 || snakeX > cols*blockSize || snakeY < 0 || snakeY > rows*blockSize) gameOver = true;
for (let i = 0; i < snakeBody.length; i++) if (snakeX === snakeBody[i][0] && snakeY === snakeBody[i][1]) gameOver = true;
if(gameOver) {
alert("Game Over");
location.reload();
}
};
const applyKey = (key) => {
if (key === "ArrowUp" && velocityY !== 1) {
velocityX = 0;
velocityY = -1;
} else if (key === "ArrowDown" && velocityY !== -1) {
velocityX = 0;
velocityY = 1;
} else if (key === "ArrowLeft" && velocityX !== 1) {
velocityX = -1;
velocityY = 0;
} else if (key === "ArrowRight" && velocityX !== -1) {
velocityX = 1;
velocityY = 0;
}
};
const changeDirection = (e) => {
applyKey(e.code);
};
const placeFood = () => {
foodX = Math.floor(Math.random() * cols) * blockSize;
foodY = Math.floor(Math.random() * rows) * blockSize;
};
const load = () => {
board = document.getElementById("board");
board.height = rows * blockSize;
board.width = cols * blockSize;
context = board.getContext("2d");
placeFood();
document.addEventListener("keyup", changeDirection);
setInterval(update, 100);
};
const getTouches = (evt) => {
return evt.touches || // browser API
evt.originalEvent.touches; // jQuery
};
const handleTouchStart = (evt) => {
const firstTouch = getTouches(evt)[0];
console.log("handleTouchStart: ", firstTouch);
xDown = firstTouch.clientX;
yDown = firstTouch.clientY;
};
const handleTouchMove = (evt) => {
if (!xDown || ! yDown) return;
var xUp = evt.touches[0].clientX;
var yUp = evt.touches[0].clientY;
var xDiff = xDown - xUp;
var yDiff = yDown - yUp;
if (Math.abs(xDiff) > Math.abs(yDiff)) {
if (xDiff > 0) {
/* right swipe */
console.log("Right");
applyKey("ArrowRight");
} else {
/* left swipe */
console.log("Left");
applyKey("ArrowLeft");
}
} else {
if (yDiff > 0) {
/* down swipe */
console.log("Down");
applyKey("ArrowDown");
} else {
/* up swipe */
console.log("Up");
applyKey("ArrowUp");
}
}
/* reset values */
xDown = null;
yDown = null;
};
// Initialization
window.addEventListener("load", load);
if (supportsTouch) {
document.addEventListener('touchstart', handleTouchStart, false);
document.addEventListener('touchmove', handleTouchMove, false);
}