我想寫一個蛇的變體,蛇從牆壁「反彈」。JS蛇遊戲中的碰撞檢測錯誤
它大部分時間都在使用,但偶爾蛇會「逃脫」,我不知道爲什麼。起初,我將碰撞檢測功能中的不等式設置爲嚴格爲<
或>
,我認爲這是問題的原因,但我已將它們更改爲<=
和>=
,問題依然存在。
任何人都可以解釋爲什麼發生這種情況嗎? (你通常需要一分鐘左右的蛇逃脫前玩...)
<canvas id="canvas" width=500 height=500 style="display: block; border: 1px solid green; margin: auto;"></canvas>
<script>
var ctx = document.getElementById('canvas').getContext('2d');
ctx.font = '30px Arial';
var HEIGHT = 500;
var WIDTH = 500;
var SEGMENT_WIDTH = 30;
var snakeVelocity = {
i: 1,
j: 0
};
var snakeArray = createSnake();
function createSnake() {
var snakeArray = [];
var length = 5; // Initial length of snake
for (var i = 0; i < length; i++) {
snakeArray.push({
x: i + 1,
y: 1
});
}
return snakeArray;
}
function moveSnake(arr) {
var head = arr.slice(-1)[0];
var tail = arr[0];
var newHead = arr.shift();
// check for wall collision, which also updates velocity if needed
snakeWallCollision(head);
newHead.x = head.x + snakeVelocity.i;
newHead.y = head.y + + snakeVelocity.j;
arr.push(newHead);
return arr;
}
function snakeWallCollision(obj) {
var collision = false;
if (obj.x >= WIDTH/SEGMENT_WIDTH || obj.x <= 0) {
snakeVelocity.i *= -1;
collision = true;
}
if (obj.y >= HEIGHT/SEGMENT_WIDTH || obj.y <= 0) {
snakeVelocity.j *= -1;
collision = true;
}
return collision;
}
function drawSnake() {
console.log(snakeArray[0]);
for (var i = 0; i < snakeArray.length; i++) {
var segment = snakeArray[i];
ctx.fillText('S', segment.x * SEGMENT_WIDTH, segment.y * SEGMENT_WIDTH + 30);
}
}
function update() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
moveSnake(snakeArray);
drawSnake();
}
function checkKey(e) {
e = e || window.event;
if ([38, 40, 37, 39].includes(e.keyCode)) {
e.preventDefault();
}
if (e.keyCode == '38') {
snakeVelocity = {
i: 0,
j: -1
};
} else if (e.keyCode == '40') {
snakeVelocity = {
i: 0,
j: 1
};
} else if (e.keyCode == '37') {
snakeVelocity = {
i: -1,
j: 0
};
} else if (e.keyCode == '39') {
snakeVelocity = {
i: 1,
j: 0
};
}
}
document.onkeydown = checkKey;
setInterval(update, 1000/20);
drawSnake();
</script>
這似乎很好地解決它。謝謝。 – Robin