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snake.js
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snake.js
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var snake = {
state: {},
_el_container: null,
_el_target: null,
_el_segments: [],
size: 10, // Size in pixel of Snake & Block
speed: 500, // Speed of Snake in miliseconds; higher number = slower
speedup: 1.1, // Speed increase after munching a Block; higher number = more speed gain
snake_color: "#33c33c", // Snake color
target_color: "#c333c3", // Blocks color
body_bg: "#eeeeee", // Main background color
fail_bg: "#990000", // Background color on collision (game fail)
init_draw: function () {
snake._el_container = document.createElement('div');
document.body.appendChild(snake._el_container);
document.body.style.overflow = "hidden";
},
draw_state: function () {
if (snake._el_target === null) {
snake._el_target = document.createElement('div');
snake._el_target.style.position = "absolute";
snake._el_target.style.height = snake.size+"px";
snake._el_target.style.width = snake.size+"px";
snake._el_target.style.background = snake.target_color;
snake._el_container.appendChild(snake._el_target);
}
snake._el_target.style.left = snake.state.target[0]+"px";
snake._el_target.style.top = snake.state.target[1]+"px";
while (snake._el_segments.length > snake.state.segments.length) {
var el = snake._el_segments.shift();
snake._el_container.removeChild(el);
}
while (snake.state.segments.length > snake._el_segments.length) {
var i = snake._el_segments.length;
var el_seg = document.createElement('div');
el_seg.style.position = "absolute";
el_seg.style.height = snake.size+"px";
el_seg.style.width = snake.size+"px";
el_seg.style.background = snake.snake_color;
el_seg.style.left = snake.state.segments[i][0]+"px";
el_seg.style.top = snake.state.segments[i][1]+"px";
snake._el_segments.push(el_seg);
snake._el_container.appendChild(el_seg);
}
for (var j = 0; j < snake.state.segments.length; j++) {
snake._el_segments[j].style.left = snake.state.segments[j][0]+"px";
snake._el_segments[j].style.top = snake.state.segments[j][1]+"px";
}
},
iterate: function () {
// Cut the tail
var tail = snake.state.segments.shift();
// Create the new head
var newseg = (
snake.state.segments.length > 0
? snake.state.segments[snake.state.segments.length - 1].slice(0)
: tail
);
newseg[0] = (newseg[0] + snake.state.direction[0] * snake.size) % window.innerWidth;
if (newseg[0] < 0) {
newseg[0] += window.innerWidth;
}
newseg[0] -= newseg[0] % snake.size;
newseg[1] = (newseg[1] + snake.state.direction[1] * snake.size) % window.innerHeight;
if (newseg[1] < 0) {
newseg[1] += window.innerHeight;
}
newseg[1] -= newseg[1] % snake.size;
snake.state.segments.push(newseg);
if (newseg[0] === snake.state.target[0] && newseg[1] === snake.state.target[1]) {
snake.add_segment();
snake.state.target = snake.random_position();
snake.state.speed *= snake.speedup;
}
if (snake.has_collision()) {
snake.lose();
snake.clear_state();
}
snake.draw_state();
snake.save_state();
window.setTimeout(snake.iterate, snake.speed / snake.state.speed);
},
_bg_red: function () {
document.body.style.background = snake.fail_bg;
},
_bg_white: function () {
document.body.style.background = snake.body_bg;
},
lose: function () {
window.setTimeout(snake._bg_red, 0);
window.setTimeout(snake._bg_white, 150);
window.setTimeout(snake._bg_red, 300);
window.setTimeout(snake._bg_white, 450);
window.setTimeout(snake._bg_red, 600);
window.setTimeout(snake._bg_white, 750);
},
has_collision: function () {
for (var i = 0; i < snake.state.segments.length; i++) {
for (var j = 0; j < snake.state.segments.length; j++) {
if (i === j) continue;
if ((snake.state.segments[i][0] === snake.state.segments[j][0]) && (snake.state.segments[i][1] === snake.state.segments[j][1]))
return true;
}
}
return false;
},
add_segment: function () {
var newseg = snake.state.segments[snake.state.segments.length - 1].slice(0);
newseg[0] = (newseg[0] + snake.state.direction[0] * snake.size) % window.innerWidth;
if (newseg[0] < 0) {
newseg[0] += window.innerWidth;
}
newseg[0] -= newseg[0] % snake.size;
newseg[1] = (newseg[1] + snake.state.direction[1] * snake.size) % window.innerHeight;
if (newseg[1] < 0) {
newseg[1] += window.innerHeight;
}
newseg[1] -= newseg[1] % snake.size;
snake.state.segments.push(newseg);
},
random_position: function () {
var h = window.innerHeight - 220 - 20,
w = window.innerWidth - 20;
var basex = Math.round(Math.random() * w),
basey = Math.round(Math.random() * h);
return [10 + basex - (basex % snake.size), 230 + basey - (basey % snake.size)];
},
start_state: function () {
return {
target: snake.random_position(),
segments: [[0, Math.min(310, (window.innerHeight - (window.innerHeight % snake.size)) - 20)]],
speed: 5,
direction: [1, 0]
};
},
load_state: function () {
var raw = window.sessionStorage.getItem('snake_state');
if (raw === null) {
snake.state = snake.start_state();
} else {
snake.state = JSON.parse(raw);
}
},
save_state: function () {
window.sessionStorage.setItem('snake_state', JSON.stringify(snake.state));
},
clear_state: function () {
window.sessionStorage.removeItem('snake_state');
snake.state = snake.start_state();
snake.draw_state();
},
keydown: function (event) {
var keyCode = event.which || event.keyCode;
if (keyCode === 40) {
// down
snake.state.direction = [0, 1];
} else if (keyCode === 38) {
// up
snake.state.direction = [0, -1];
} else if (keyCode === 37) {
// left
snake.state.direction = [-1, 0];
} else if (keyCode === 39) {
// right
snake.state.direction = [1, 0];
} else if (keyCode === 27) {
// escape
snake.clear_state(); // Reset the game
}
},
_touch_start: null,
touch_start: function (event) {
var touches = event.changedTouches;
snake._touch_start = [touches[0].pageX, touches[0].pageY];
},
touch_end: function (event) {
var touches = event.changedTouches;
var end_pos = [touches[0].pageX, touches[0].pageY];
var dX = end_pos[0] - snake._touch_start[0],
dY = end_pos[1] - snake._touch_start[1],
c = Math.sqrt(dX*dX + dY*dY),
alpha = Math.acos(dX/c);
if (alpha < Math.PI * 1/4) {
snake.state.direction = [1, 0];
} else if (alpha > Math.PI * 3/4) {
snake.state.direction = [-1, 0];
} else if (dY > 0) {
snake.state.direction = [0, 1];
} else {
snake.state.direction = [0, -1];
}
},
init: function () {
snake.load_state();
snake.init_draw();
snake.draw_state();
window.onkeydown = snake.keydown;
document.body.addEventListener("touchstart", snake.touch_start, false);
document.body.addEventListener("touchend", snake.touch_end, false);
window.setTimeout(snake.iterate, 500);
}
};
window.onload = snake.init();