html5 canvas走出迷宫小游戏，代码简洁，适合学习

<canvas id="canvas"></canvas>
<p>使用左键、右键和上箭头键移动。</p>
<p class="info">地图数据是完全可定制和可编写脚本（全部包含在“地图”的变量）。请参见代码中的注释以获得说明。</p>
<script>
/* Customisable map data */
var map = {
    tile_size: 16,
    /*
    Key vairables:
    id       [required] - an integer that corresponds with a tile in the data array.
    colour   [required] - any javascript compatible colour variable.
    solid    [optional] - whether the tile is solid or not, defaults to false.
    bounce   [optional] - how much velocity is preserved upon hitting the tile, 0.5 is half.
    jump     [optional] - whether the player can jump while over the tile, defaults to false.
    friction [optional] - friction of the tile, must have X and Y values (e.g {x:0.5, y:0.5}).
    gravity  [optional] - gravity of the tile, must have X and Y values (e.g {x:0.5, y:0.5}).
    fore     [optional] - whether the tile is drawn in front of the player, defaults to false.
    script   [optional] - refers to a script in the scripts section, executed if it is touched.
    */
    keys: [
        {id: 0, colour: '#333', solid: 0},
        {id: 1, colour: '#888', solid: 0},
        {id: 2,colour: '#555',solid: 1,bounce: 0.35},
        {id: 3,colour: 'rgba(121, 220, 242, 0.4)',friction: {x: 0.9,y: 0.9},gravity: {x: 0,y: 0.1},jump: 1,fore: 1},
        {id: 4,colour: '#777',jump: 1},
        {id: 5,colour: '#E373FA',solid: 1,bounce: 1.1},
        {id: 6,colour: '#666',solid: 1,bounce: 0},
        {id: 7,colour: '#73C6FA',solid: 0,script: 'change_colour'},
        {id: 8,colour: '#FADF73',solid: 0,script: 'next_level'},
        {id: 9,colour: '#C93232',solid: 0,script: 'death'},
        {id: 10,colour: '#555',solid: 1},
        {id: 11,colour: '#0FF',solid: 0,script: 'unlock'}
    ],
    /* An array representing the map tiles. Each number corresponds to a key */
    data: [
        [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 6, 6, 6, 6, 6, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 1, 1, 1, 1, 1, 2, 2, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 7, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 2, 2, 2, 4, 2, 2, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2, 2, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, 4, 2, 1, 2],
        [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2],
        [2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 2],
        [2, 1, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 2],
        [2, 1, 2, 2, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 4, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 2],
        [2, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 4, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 8, 1, 1, 1, 2],
        [2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 6, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2],
        [2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 9, 9, 9, 2, 10, 10, 10, 10, 10, 10, 1, 1, 1, 1, 1, 1, 1, 11, 2, 2, 2, 2, 4, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 10, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 2, 2, 2, 2, 2, 2, 2],
        [2, 6, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 2, 1, 1, 1, 1, 1, 1, 2],
        [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 4, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 1, 2],
        [2, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 6, 6, 6, 2, 2, 2, 2, 2, 2, 6, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2],
        [2, 1, 1, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 2, 1, 1, 1, 1, 2, 5, 5, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 1, 1, 1, 1, 1, 1, 1, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2],
        [2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 5, 5, 5, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 2],
        [2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2]
    ],
    /* Default gravity of the map */
    gravity: {
        x: 0,
        y: 0.3
    },
    /* Velocity limits */
    vel_limit: {
        x: 2,
        y: 16
    },
    /* Movement speed when the key is pressed */
    movement_speed: {
        jump: 6,
        left: 0.3,
        right: 0.3
    },
    /* The coordinates at which the player spawns and the colour of the player */
    player: {
        x: 2,
        y: 2,
        colour: '#FF9900'
    },
    /* scripts refered to by the "script" variable in the tile keys */
    scripts: {
        /* you can just use "this" instead of your engine variable ("game"), but Codepen doesn't like it */
        change_colour: 'game.player.colour = "#"+(Math.random()*0xFFFFFF<<0).toString(16);',
        /* you could load a new map variable here */
        next_level: 'alert("Yay! You won! Reloading map.");game.load_map(map);',
        death: 'alert("You died!");game.load_map(map);',
        unlock: 'game.current_map.keys[10].solid = 0;game.current_map.keys[10].colour = "#888";'
    }
};
/* Clarity engine */
var Clarity = function () {
    this.alert_errors   = false;
    this.log_info       = true;
    this.tile_size      = 16;
    this.limit_viewport = false;
    this.jump_switch    = 0;
    this.viewport = {
        x: 200,
        y: 200
    };
    this.camera = {
        x: 0,
        y: 0
    };
    this.key = {
        left: false,
        right: false,
        up: false
    };
    this.player = {
        loc: {
            x: 0,
            y: 0
        },
        vel: {
            x: 0,
            y: 0
        },
        can_jump: true
    };
    window.onkeydown = this.keydown.bind(this);
    window.onkeyup   = this.keyup.bind(this);
};
Clarity.prototype.error = function (message) {
    if (this.alert_errors) alert(message);
    if (this.log_info) console.log(message);
};
Clarity.prototype.log = function (message) {
    if (this.log_info) console.log(message);
};
Clarity.prototype.set_viewport = function (x, y) {
    this.viewport.x = x;
    this.viewport.y = y;
};
Clarity.prototype.keydown = function (e) {
    var _this = this;
    switch (e.keyCode) {
    case 37:
        _this.key.left = true;
        break;
    case 38:
        _this.key.up = true;
        break;
    case 39:
        _this.key.right = true;
        break;
    }
};
Clarity.prototype.keyup = function (e) {
    var _this = this;
    switch (e.keyCode) {
    case 37:
        _this.key.left = false;
        break;
    case 38:
        _this.key.up = false;
        break;
    case 39:
        _this.key.right = false;
        break;
    }
};
Clarity.prototype.load_map = function (map) {
    if (typeof map      === 'undefined'
     || typeof map.data === 'undefined'
     || typeof map.keys === 'undefined') {
        this.error('Error: Invalid map data!');
        return false;
    }
    this.current_map = map;
    this.current_map.background = map.background || '#333';
    this.current_map.gravity = map.gravity || {x: 0, y: 0.3};
    this.tile_size = map.tile_size || 16;
    var _this = this;
    this.current_map.width = 0;
    this.current_map.height = 0;
    map.keys.forEach(function (key) {
        map.data.forEach(function (row, y) {
            _this.current_map.height = Math.max(_this.current_map.height, y);
            row.forEach(function (tile, x) {
                _this.current_map.width = Math.max(_this.current_map.width, x);
                if (tile == key.id)
                    _this.current_map.data[y][x] = key;
            });
        });
    });
    this.current_map.width_p = this.current_map.width * this.tile_size;
    this.current_map.height_p = this.current_map.height * this.tile_size;
    this.player.loc.x = map.player.x * this.tile_size || 0;
    this.player.loc.y = map.player.y * this.tile_size || 0;
    this.player.colour = map.player.colour || '#000';
    this.key.left  = false;
    this.key.up    = false;
    this.key.right = false;
    this.camera = {
        x: 0,
        y: 0
    };
    this.player.vel = {
        x: 0,
        y: 0
    };
    this.log('Successfully loaded map data.');
    return true;
};
Clarity.prototype.get_tile = function (x, y) {
    return (this.current_map.data[y] && this.current_map.data[y][x]) ? this.current_map.data[y][x] : 0;
};
Clarity.prototype.draw_tile = function (x, y, tile, context) {
    if (!tile || !tile.colour) return;
    context.fillStyle = tile.colour;
    context.fillRect(
        x,
        y,
        this.tile_size,
        this.tile_size
    );
};
Clarity.prototype.draw_map = function (context, fore) {
    for (var y = 0; y < this.current_map.data.length; y++) {
        for (var x = 0; x < this.current_map.data[y].length; x++) {
            if ((!fore && !this.current_map.data[y][x].fore) || (fore && this.current_map.data[y][x].fore)) {
                var t_x = (x * this.tile_size) - this.camera.x;
                var t_y = (y * this.tile_size) - this.camera.y;
                if(t_x < -this.tile_size
                || t_y < -this.tile_size
                || t_x > this.viewport.x
                || t_y > this.viewport.y) continue;
                this.draw_tile(
                    t_x,
                    t_y,
                    this.current_map.data[y][x],
                    context
                );
            }
        }
    }
    if (!fore) this.draw_map(context, true);
};
Clarity.prototype.move_player = function () {
    var tX = this.player.loc.x + this.player.vel.x;
    var tY = this.player.loc.y + this.player.vel.y;
    var offset = Math.round((this.tile_size / 2) - 1);
    var tile = this.get_tile(
        Math.round(this.player.loc.x / this.tile_size),
        Math.round(this.player.loc.y / this.tile_size)
    );
    if(tile.gravity) {
        this.player.vel.x += tile.gravity.x;
        this.player.vel.y += tile.gravity.y;
    } else {
        this.player.vel.x += this.current_map.gravity.x;
        this.player.vel.y += this.current_map.gravity.y;
    }
    if (tile.friction) {
        this.player.vel.x *= tile.friction.x;
        this.player.vel.y *= tile.friction.y;
    }
    var t_y_up   = Math.floor(tY / this.tile_size);
    var t_y_down = Math.ceil(tY / this.tile_size);
    var y_near1  = Math.round((this.player.loc.y - offset) / this.tile_size);
    var y_near2  = Math.round((this.player.loc.y + offset) / this.tile_size);
    var t_x_left  = Math.floor(tX / this.tile_size);
    var t_x_right = Math.ceil(tX / this.tile_size);
    var x_near1   = Math.round((this.player.loc.x - offset) / this.tile_size);
    var x_near2   = Math.round((this.player.loc.x + offset) / this.tile_size);
    var top1    = this.get_tile(x_near1, t_y_up);
    var top2    = this.get_tile(x_near2, t_y_up);
    var bottom1 = this.get_tile(x_near1, t_y_down);
    var bottom2 = this.get_tile(x_near2, t_y_down);
    var left1   = this.get_tile(t_x_left, y_near1);
    var left2   = this.get_tile(t_x_left, y_near2);
    var right1  = this.get_tile(t_x_right, y_near1);
    var right2  = this.get_tile(t_x_right, y_near2);
    if (tile.jump && this.jump_switch > 15) {
        this.player.can_jump = true;
        this.jump_switch = 0;
    } else this.jump_switch++;
    this.player.vel.x = Math.min(Math.max(this.player.vel.x, -this.current_map.vel_limit.x), this.current_map.vel_limit.x);
    this.player.vel.y = Math.min(Math.max(this.player.vel.y, -this.current_map.vel_limit.y), this.current_map.vel_limit.y);
    this.player.loc.x += this.player.vel.x;
    this.player.loc.y += this.player.vel.y;
    this.player.vel.x *= .9;
    if (left1.solid || left2.solid || right1.solid || right2.solid) {
        /* fix overlap */
        while (this.get_tile(Math.floor(this.player.loc.x / this.tile_size), y_near1).solid
            || this.get_tile(Math.floor(this.player.loc.x / this.tile_size), y_near2).solid)
            this.player.loc.x += 0.1;
        while (this.get_tile(Math.ceil(this.player.loc.x / this.tile_size), y_near1).solid
            || this.get_tile(Math.ceil(this.player.loc.x / this.tile_size), y_near2).solid)
            this.player.loc.x -= 0.1;
        /* tile bounce */
        var bounce = 0;
        if (left1.solid && left1.bounce > bounce) bounce = left1.bounce;
        if (left2.solid && left2.bounce > bounce) bounce = left2.bounce;
        if (right1.solid && right1.bounce > bounce) bounce = right1.bounce;
        if (right2.solid && right2.bounce > bounce) bounce = right2.bounce;
        this.player.vel.x *= -bounce || 0;
    }
    if (top1.solid || top2.solid || bottom1.solid || bottom2.solid) {
        /* fix overlap */
        while (this.get_tile(x_near1, Math.floor(this.player.loc.y / this.tile_size)).solid
            || this.get_tile(x_near2, Math.floor(this.player.loc.y / this.tile_size)).solid)
            this.player.loc.y += 0.1;
        while (this.get_tile(x_near1, Math.ceil(this.player.loc.y / this.tile_size)).solid
            || this.get_tile(x_near2, Math.ceil(this.player.loc.y / this.tile_size)).solid)
            this.player.loc.y -= 0.1;
        /* tile bounce */
        var bounce = 0;
        if (top1.solid && top1.bounce > bounce) bounce = top1.bounce;
        if (top2.solid && top2.bounce > bounce) bounce = top2.bounce;
        if (bottom1.solid && bottom1.bounce > bounce) bounce = bottom1.bounce;
        if (bottom2.solid && bottom2.bounce > bounce) bounce = bottom2.bounce;
        this.player.vel.y *= -bounce || 0;
        if ((bottom1.solid || bottom2.solid) && !tile.jump) {
            this.player.on_floor = true;
            this.player.can_jump = true;
        }
    }
    // adjust camera
    var c_x = Math.round(this.player.loc.x - this.viewport.x/2);
    var c_y = Math.round(this.player.loc.y - this.viewport.y/2);
    var x_dif = Math.abs(c_x - this.camera.x);
    var y_dif = Math.abs(c_y - this.camera.y);
    if(x_dif > 5) {
        var mag = Math.round(Math.max(1, x_dif * 0.1));
        if(c_x != this.camera.x) {
            this.camera.x += c_x > this.camera.x ? mag : -mag;
            if(this.limit_viewport) {
                this.camera.x = 
                    Math.min(
                        this.current_map.width_p - this.viewport.x + this.tile_size,
                        this.camera.x
                    );
                this.camera.x = 
                    Math.max(
                        0,
                        this.camera.x
                    );
            }
        }
    }
    if(y_dif > 5) {
        var mag = Math.round(Math.max(1, y_dif * 0.1));
        if(c_y != this.camera.y) {
            this.camera.y += c_y > this.camera.y ? mag : -mag;
            if(this.limit_viewport) {
                this.camera.y = 
                    Math.min(
                        this.current_map.height_p - this.viewport.y + this.tile_size,
                        this.camera.y
                    );
                this.camera.y = 
                    Math.max(
                        0,
                        this.camera.y
                    );
            }
        }
    }
    if(this.last_tile != tile.id && tile.script) {
        eval(this.current_map.scripts[tile.script]);
    }
    this.last_tile = tile.id;
};
Clarity.prototype.update_player = function () {
    if (this.key.left) {
        if (this.player.vel.x > -this.current_map.vel_limit.x)
            this.player.vel.x -= this.current_map.movement_speed.left;
    }
    if (this.key.up) {
        if (this.player.can_jump && this.player.vel.y > -this.current_map.vel_limit.y) {
            this.player.vel.y -= this.current_map.movement_speed.jump;
            this.player.can_jump = false;
        }
    }
    if (this.key.right) {
        if (this.player.vel.x < this.current_map.vel_limit.x)
            this.player.vel.x += this.current_map.movement_speed.left;
    }
    this.move_player();
};
Clarity.prototype.draw_player = function (context) {
    context.fillStyle = this.player.colour;
    context.beginPath();
    context.arc(
        this.player.loc.x + this.tile_size / 2 - this.camera.x,
        this.player.loc.y + this.tile_size / 2 - this.camera.y,
        this.tile_size / 2 - 1,
        0,
        Math.PI * 2
    );
    context.fill();
};
Clarity.prototype.update = function () {
    this.update_player();
};
Clarity.prototype.draw = function (context) {
    this.draw_map(context, false);
    this.draw_player(context);
};
/* Setup of the engine */
window.requestAnimFrame =
  window.requestAnimationFrame ||
  window.webkitRequestAnimationFrame ||
  window.mozRequestAnimationFrame ||
  window.oRequestAnimationFrame ||
  window.msRequestAnimationFrame ||
  function(callback) {
    return window.setTimeout(callback, 1000 / 60);
  };
var canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d');
canvas.width = 400;
canvas.height = 400;
var game = new Clarity();
    game.set_viewport(canvas.width, canvas.height);
    game.load_map(map);
    /* Limit the viewport to the confines of the map */
    game.limit_viewport = true;
var Loop = function() {
  ctx.fillStyle = '#333';
  ctx.fillRect(0, 0, canvas.width, canvas.height);
  game.update();
  game.draw(ctx);
  window.requestAnimFrame(Loop);
};
Loop();
</script>