games/lesson_21_terrain_kernel.html

<!DOCTYPE html>
<html>
<meta charset="utf-8"/>
<!--
- Fill the screen with the game environment. No scrolling
- Top portion of screen is game panel, bottom region console
- Set up a basic web GL canvas environment that we"ll use to draw the game
- Move setup code into a library ("gpgpu")
- Add bounded rendering region, with view scale and coordinates
- Add mouse control: drag to pan, scroll wheel to zoom in/out
- Add keyboard control: arrow keys to pan; +/- PgUp/PgDn to zoom
- Render an image from texture using nearest-neighbor interpolation
- Create a 2D game environment based on square tiles
- Build a game of life demo using the tiles 

- Slightly fancier drawing example


Composit multiple fields? This would require modifying tile shader to support 
layers. And colors. Probably not a bad thing to add. I think the easiest way to 
do this is to call the tile shader multiple times and then manually composit. 
Pretty inefficient though. Still, no need for premature optimiziation.

Main thing to add to this will be some sort of button panel. This would be 
another WebGL canvas I suppose? 

Useful
https://webgl2fundamentals.org/webgl/lessons/webgl-anti-patterns.html
https://stackoverflow.com/questions/13870677/resize-viewport-canvas-according-to-browser-window-size
https://github.com/michaelerule/webgpgpu
https://stackoverflow.com/a/7732968/900749
https://www.w3schools.com/js/js_htmldom_events.asp
https://javascript.info/introduction-browser-events
https://developer.mozilla.org/en-US/docs/Web/Events
https://stackoverflow.com/a/11183302/900749
https://stackoverflow.com/a/11183333/900749
https://www.javascripttutorial.net/javascript-dom/javascript-keyboard-events/
https://github.com/michaelerule/webgpgpu/blob/master/examples/Example_15_load_image.html
https://webglfundamentals.org/webgl/lessons/webgl-cors-permission.html
https://stackoverflow.com/questions/21540520/how-to-perform-mipmapping-in-webgl444https://stackoverflow.com/questions/6171932/webgl-reading-pixel-data-from-render-buffer
https://dannywoodz.wordpress.com/2015/10/14/webgl-from-scratch-updating-textures/
https://stackoverflow.com/questions/13626606/read-pixels-from-a-webgl-textures
https://developer.mozilla.org/en-US/docs/Web/API/WebGLRenderingContext/readPixels

Packing pixels:
https://stackoverflow.com/questions/22895237/hexadecimal-to-rgb-values-in-webgl-shader
-->
<head>
<script>
window.addEventListener("load", function() {load_textures();})
</script>
<script src="./lib/gpgpu.js"></script>
<script src="./lib/gpurand.js"></script>
<script src="./lib/parameters.js"></script>
<script src="./webgl_game_initialization_helpers.js"></script>
<script src="./base64_encoded_textures.js"></script>
<link rel="stylesheet" type="text/css" href="lessons.css">
</head>
<body>
<div id="outer_container">
<canvas id="game_canvas"></canvas>
<canvas id="controls_canvas"></canvas>
</div>

<script id="boxes_parameters" type="x-shader/x-fragment">
sampler2D game_state;
vec2 game_size;
</script>
<script id="boxes" type="x-shader/x-fragment">
#define BOX    (176-48)
#define EMPTY  (240)
#define NEIGHBOR(q) ivec4(equal(texture2D(game_state,q),s))*t
void main() {
    vec2 dx = vec2(1.0/game_size.x,0.0);
    vec2 dy = vec2(0.0,1.0/game_size.y);
    vec2  p = gl_FragCoord.xy/game_size;
    vec4  s = texture2D(game_state,p);
    ivec4 tid = ivec4(s*255.0);
    ivec4 t   = ivec4(notEqual(tid,ivec4(EMPTY)));
    ivec4 s11 = t;
    ivec4 s01 = NEIGHBOR(p-dy);
    ivec4 s10 = NEIGHBOR(p-dx);
    ivec4 s12 = NEIGHBOR(p+dx);
    ivec4 s21 = NEIGHBOR(p+dy);
    ivec4 s00 = NEIGHBOR(p-dy-dx);
    ivec4 s02 = NEIGHBOR(p-dy+dx);
    ivec4 s20 = NEIGHBOR(p+dy-dx);
    ivec4 s22 = NEIGHBOR(p+dy+dx);
    ivec4 id  = s21+s12*2+s01*4+s10*8;
    //id += ivec4(equal(id,ivec4( 3)))*ivec4(equal(s22,ivec4(1)))*(16-id);
    //id += ivec4(equal(id,ivec4( 6)))*ivec4(equal(s02,ivec4(1)))*(17-id);
    //id += ivec4(equal(id,ivec4( 9)))*ivec4(equal(s20,ivec4(1)))*(18-id);
    //id += ivec4(equal(id,ivec4(12)))*ivec4(equal(s00,ivec4(1)))*(19-id);
    //ivec4 c;
    //c = s22+s02*2;
    //id += ivec4(equal(id,ivec4( 7)))*ivec4(greaterThan(c,ivec4(0)))*(19+c-id);
    //id += ivec4(equal(id,ivec4( 7)))*ivec4(greaterThan(c,ivec4(0)))*(19+c-id);
    //c = s20+s22*2;
    //id += ivec4(equal(id,ivec4(11)))*ivec4(greaterThan(c,ivec4(0)))*(22+c-id);
    //c = s00+s20*2;
    //id += ivec4(equal(id,ivec4(13)))*ivec4(greaterThan(c,ivec4(0)))*(25+c-id);
    //c = s02+s00*2;
    //id += ivec4(equal(id,ivec4(14)))*ivec4(greaterThan(c,ivec4(0)))*(28+c-id);

    int c;
    
    if      (id.r== 3) {if (s22.r==1) id.r=16;}
    else if (id.r== 6) {if (s02.r==1) id.r=17;}
    else if (id.r== 9) {if (s20.r==1) id.r=18;}
    else if (id.r==12) {if (s00.r==1) id.r=19;}
    else if (id.r== 7) {c=s22.r+s02.r*2; if (c>0) id.r=19+c;}
    else if (id.r==11) {c=s20.r+s22.r*2; if (c>0) id.r=22+c;}
    else if (id.r==13) {c=s00.r+s20.r*2; if (c>0) id.r=25+c;}
    else if (id.r==14) {c=s02.r+s00.r*2; if (c>0) id.r=28+c;}
    else if (id.r==15) {c=s20.r+s22.r*2+s02.r*4+s00.r*8; id.r=(c>0)?31+c:15;}
    
    if      (id.g== 3) {if (s22.g==1) id.g=16;}
    else if (id.g== 6) {if (s02.g==1) id.g=17;}
    else if (id.g== 9) {if (s20.g==1) id.g=18;}
    else if (id.g==12) {if (s00.g==1) id.g=19;}
    else if (id.g== 7) {c=s22.g+s02.g*2; if (c>0) id.g=19+c;}
    else if (id.g==11) {c=s20.g+s22.g*2; if (c>0) id.g=22+c;}
    else if (id.g==13) {c=s00.g+s20.g*2; if (c>0) id.g=25+c;}
    else if (id.g==14) {c=s02.g+s00.g*2; if (c>0) id.g=28+c;}
    else if (id.g==15) {c=s20.g+s22.g*2+s02.g*4+s00.g*8; id.g=(c>0)?31+c:15;}
    
    if      (id.b== 3) {if (s22.b==1) id.b=16;}
    else if (id.b== 6) {if (s02.b==1) id.b=17;}
    else if (id.b== 9) {if (s20.b==1) id.b=18;}
    else if (id.b==12) {if (s00.b==1) id.b=19;}
    else if (id.b== 7) {c=s22.b+s02.b*2; if (c>0) id.b=19+c;}
    else if (id.b==11) {c=s20.b+s22.b*2; if (c>0) id.b=22+c;}
    else if (id.b==13) {c=s00.b+s20.b*2; if (c>0) id.b=25+c;}
    else if (id.b==14) {c=s02.b+s00.b*2; if (c>0) id.b=28+c;}
    else if (id.b==15) {c=s20.b+s22.b*2+s02.b*4+s00.b*8; id.b=(c>0)?31+c:15;}
    
    if      (id.a== 3) {if (s22.a==1) id.a=16;}
    else if (id.a== 6) {if (s02.a==1) id.a=17;}
    else if (id.a== 9) {if (s20.a==1) id.a=18;}
    else if (id.a==12) {if (s00.a==1) id.a=19;}
    else if (id.a== 7) {c=s22.a+s02.a*2; if (c>0) id.a=19+c;}
    else if (id.a==11) {c=s20.a+s22.a*2; if (c>0) id.a=22+c;}
    else if (id.a==13) {c=s00.a+s20.a*2; if (c>0) id.a=25+c;}
    else if (id.a==14) {c=s02.a+s00.a*2; if (c>0) id.a=28+c;}
    else if (id.a==15) {c=s20.a+s22.a*2+s02.a*4+s00.a*8; id.a=(c>0)?31+c:15;}
    
    id  = (id+BOX)*t+(1-t)*ivec4(EMPTY);
    gl_FragColor = vec4(id)/255.0;
}
</script>

<!--
Extend tile shader to handle layers. 
The R,G,B and A channels can each pass a tile ID
Tiles are rendered atop one another in order.
Black is interpreted as transparent.
-->
<script id="tile_layers_parameters" type="x-shader/x-fragment">
sampler2D tiles;
sampler2D tile_ids;
vec2  game_size;
vec2  screen_size;
vec2  texture_size;
vec2  tile_size;
vec2  select;
float tiles_across;
vec3  view_transform;
</script>
<script id="tile_layers" type="x-shader/x-fragment">
void main() {
    // Get position
    vec2 p = gl_FragCoord.xy*view_transform.z + view_transform.xy;
    if (p.x<0.0||p.y<0.0||p.x>screen_size.x||p.y>screen_size.y) return;
    
    // Round to nearest game tile and get tile IDs
    vec2 p2  = (floor(p/tile_size)+0.5)/(game_size);
    vec4 ids = 255.0-floor(texture2D(tile_ids,p2)*255.0);

    // Compute x and y positions of tiles in texture, and offset into tile
    vec4 tx = (tiles_across-1.0)-mod(ids,tiles_across);
    vec4 ty = floor(ids/tiles_across);
    vec2 td = floor(mod(p,tile_size));

    // Composit layers. Red first. Then g,b,a (but black is transparent)
    vec2 u;
    vec4 c,d=vec4(0.7);
    u = vec2(tx.r,ty.r)*tile_size;
    c = texture2D(tiles,(u+td)/(float(tiles_across)*tile_size));
    //c.a = (c.r+c.g+c.b)/3.0;
    d.rgb = d.rgb*(1.0-c.a) + c.rrr*vec3(0.5,0.4,0.4)*c.a;
    u = vec2(tx.g,ty.g)*tile_size;
    c = texture2D(tiles,(u+td)/(float(tiles_across)*tile_size));
    //c.a = (c.r+c.g+c.b)/3.0;
    d.rgb = d.rgb*(1.0-c.a) + vec3(c.r*0.5,c.g*0.5,0.0)*c.a;
    u = vec2(tx.b,ty.b)*tile_size;
    c = texture2D(tiles,(u+td)/(float(tiles_across)*tile_size));
    //c.a = (c.r+c.g+c.b)/3.0;
    d.rgb = d.rgb*(1.0-c.a) + vec3(0.0,c.g*0.6,0.0)*c.a;
    u = vec2(tx.a,ty.a)*tile_size;
    c = texture2D(tiles,(u+td)/(float(tiles_across)*tile_size));
    //c.a = (c.r+c.g+c.b)/3.0;
    d.rgb = d.rgb*(1.0-c.a) + vec3(0.0,0.0,c.b)*c.a;
    gl_FragColor = d;

    // Invert result if this is the selected tile
    vec2 r = floor(p/tile_size);
    if (r.x==floor(select.x)&&r.y==floor(select.y)) gl_FragColor=1.0-gl_FragColor;
}
</script>


<script>
// Configuration constants.
// The game size is now defined in terms of tiles. 
const game_w_tiles = 64;
const game_h_tiles = 64;
// We need to know shape of tiles in the tiles texture, and # tiles across
const tile_w       = 8;
const tile_h       = 8;
const tiles_across = 16;
// Calculated game shape in pixels
const game_w_px    = game_w_tiles*tile_w;
const game_h_px    = game_h_tiles*tile_h;
// View behavior and limits
const max_scale    = 8;
const min_scale    = 1;
const key_pan      = 10;
const key_zoom     = 1.1;

// Named tiles
const SELECT = 74;
const DELETE = 73;
const EMPTY = 240;
const BOX0  =   0;
const BOX1  =  16;
const BOX2  =  32;
const BOX3  =  48;
const BOX4  = 128;
const BOX5  = 176;
const DOWN  = 111;
const UP    = 110;
const LEFT  = 108;
const RIGHT = 109;
const IN    = 107;
const OUT   = 106; 

var game;
var controls;

var most_recent_mouse_event = null;
window.addEventListener("mousemove",(e)=>{
    most_recent_mouse_event = e;
})

/**
 * Convert mouse event to game coordinates.
 * @param e {MouseEvent} mouse event object
 */
function mouse_to_game_point(game,e) {
    var rect = game.canvas.getBoundingClientRect();
    var r = window.devicePixelRatio;
    return {x:game.focus_x+(e.clientX-rect.left-game.canvas.clientWidth /2)/game.scale*r,
            y:game.focus_y-(e.clientY-rect.top -game.canvas.clientHeight/2)/game.scale*r};
}

function get_layered_shader(gl,game_w_tiles,game_h_tiles,tile_w_px,tile_h_px,tiles_across,debug) {
    var game_w_px = game_w_tiles*tile_w_px;
    var game_h_px = game_h_tiles*tile_h_px;
    var params = {
        game_size   :[game_w_tiles,game_h_tiles],
        tile_size   :[tile_w_px   ,tile_h_px   ],
        screen_size :[game_w_px   ,game_h_px   ],
        tiles_across:tiles_across};
    return bind_program(gl,"tile_layers",params);
}

function init_tiled_canvas(name,w,h) {
    var c = {w:w,h:h};
    c.canvas  = init_webgl_canvas(name);
    c.gl      = c.canvas.gl;
    c.wpx     = c.w*tile_w;
    c.hpx     = c.h*tile_h;
    c.texels  = pixel_art_texture(c.gl,tiles);
    c.tiles   = pixel_art_buffer(c.gl,c.w,c.h);
    c.shader  = get_layered_shader(c.gl,c.w,c.h,tile_w,tile_h,tiles_across,false);
    c.select  = [-1,-1];
    c.focus_x = c.wpx/2;
    c.focus_y = c.hpx/2;
    c.scale   = 2.0;
    return c;
}


function init_controls() {
    var tw = 12;
    var th = 5;
    var controls = init_tiled_canvas("controls_canvas",tw,th);
    controls.shader  = get_tile_shader(controls.gl,controls.w,controls.h,tile_w,tile_h,tiles_across,false);
    var w = controls.gl.canvas.width;
    var h = controls.gl.canvas.height;
    controls.scale = (Math.min(w/controls.wpx,h/controls.hpx))
    controls.focus_x = controls.wpx/2;
    controls.focus_h = controls.hpx/2;
    controls.render  = ()=>{
        var w = controls.gl.canvas.width;
        var h = controls.gl.canvas.height;
        controls.gl.viewport(0,0,w,h);
        var s = 1.0/controls.scale;
        var x = Math.floor(controls.focus_x-w/2*s);
        var y = Math.floor(controls.focus_y-h/2*s);
        controls.shader({
            tiles:controls.texels,
            tile_ids:controls.tiles,
            view_transform:[x,y,s],
            select:controls.select
        });
    }

    controls.resize = (e)=>{
        c = controls.canvas;
        var w = Math.round(c.clientWidth *window.devicePixelRatio);
        var h = Math.round(c.clientHeight*window.devicePixelRatio);
        if (c.width!=w||c.height!=h) {
            c.width =w; 
            c.height=h;
            controls.scale = Math.min(w/controls.wpx,h/controls.hpx);
            controls.focus_x = controls.wpx/2;
            controls.focus_h = controls.hpx/2;
            controls.render();
        }
    };
    window.addEventListener("resize",controls.resize);

    var icons = new Uint8Array(controls.w*controls.h);
    for (var i=0; i<controls.w*controls.h; i++) icons[i]=EMPTY;
    controls.buttons = [];
    var new_button=(x,y,t,f)=>{
        icons[y*controls.w+x]=t;
        controls.buttons[t]={press:f,x:x,y:y,t:t};
    };
    new_button(0,0,EMPTY,()=>{console.log("Nothing here!")});
    var by = Math.floor((th-3)/2);
    new_button(1,by+2,SELECT,()=>{game.set_tool(SELECT);})
    new_button(1,by  ,DELETE,()=>{game.set_tool(DELETE);})
    new_button(3,by  ,BOX0  ,()=>{game.set_tool(BOX0);  })
    new_button(3,by+2,BOX1  ,()=>{game.set_tool(BOX1);  })
    new_button(5,by  ,BOX2  ,()=>{game.set_tool(BOX2);  })
    new_button(5,by+2,BOX3  ,()=>{game.set_tool(BOX3);  })
    // Arrow pad
    var ay = Math.floor(th/2);
    new_button(tw-3,ay-1,DOWN ,()=>{game.down()   })
    new_button(tw-3,ay+1,UP   ,()=>{game.up()     })
    new_button(tw-4,ay  ,LEFT ,()=>{game.left()   })
    new_button(tw-2,ay  ,RIGHT,()=>{game.right()  })
    new_button(tw-4,ay+1,IN   ,()=>{game.zoomin() })
    new_button(tw-2,ay+1,OUT  ,()=>{game.zoomout()})
    // Generate buttons as a tiled environment
    controls.icons = icons
    var data  = new Uint8Array(controls.w*controls.h*4);
    for (var i=0; i<controls.w*controls.h*4; i++) data[i] = EMPTY;
    for (var i=0; i<controls.w*controls.h; i++) data[i*4] = icons[i];
    var gl = controls.gl;
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL,false)
    gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL,false)
    gl.bindTexture  (gl.TEXTURE_2D,controls.tiles.texture);
    gl.texSubImage2D(gl.TEXTURE_2D,0,0,0,controls.w,controls.h,gl.RGBA,gl.UNSIGNED_BYTE,data);

    controls.canvas.onclick = function(e) {
        var p = mouse_to_game_point(controls,e);
        var q = {x:Math.floor(p.x/tile_w),y:Math.floor(p.y/tile_h)};
        console.log("Controls click",p,q);
        controls.render();
        if (q.x>=0&&q.x<controls.w&&q.y>=0&&q.y<controls.h) {
            var tile   = icons[q.x+controls.w*q.y];
            var button = controls.buttons[tile];
            if (button) button.press();
        }
    };

    // TODO: render should have been defined before this happens
    controls.noselect=(e)=>{
        q = controls.buttons[game.tool];
        controls.select=[q.x,q.y];
        controls.render();
        console.log("hi");
    }
    controls.update_mouse_highlight=(e)=>{
        var p = mouse_to_game_point(controls,e);
        var button_state = e.buttons===undefined?e.which:e.buttons;
        var isdown = !!(button_state&1);
        if (isdown) controls.select=[-1,-1]
        else {
            var q={x:Math.floor(p.x/tile_w),y:Math.floor(p.y/tile_h)};
            if (q.x>=0&&q.y>=0&&q.x<controls.w&&q.y<controls.h)
                controls.select=[q.x,q.y];
            else controls.noselect();
        }
        controls.render();
    };
    controls.canvas.addEventListener("mousemove",controls.update_mouse_highlight);
    controls.canvas.addEventListener("mousedown",controls.update_mouse_highlight);
    controls.canvas.addEventListener("mouseup"  ,controls.update_mouse_highlight);
    window.addEventListener("keyup",(e)=>{
        controls.update_mouse_highlight(most_recent_mouse_event)
    });

    controls.canvas.addEventListener("mouseleave",controls.noselect);
    controls.canvas.addEventListener("mouseout"  ,controls.noselect);

    return controls;
}

function init_game() {
    var game = init_tiled_canvas("game_canvas",game_w_tiles,game_h_tiles);

    game.render = ()=>{
        var w = game.canvas.width;
        var h = game.canvas.height;
        game.gl.viewport(0,0,w,h);
        var s = 1.0/game.scale;
        var x = Math.floor(game.focus_x-w/2*s);
        var y = Math.floor(game.focus_y-h/2*s);
        game.shader({
            tiles:game.texels,
            tile_ids:game.tiles,
            view_transform:[x,y,s],
            select:game.select
        });
    };

    // Kernels and framebuffers
    game.boxes  = bind_program(game.gl,"boxes" ,{game_size:[game.w,game.h]});
    game.copy   = GPUcopy(game.gl,{W:game.w,H:game.h})
    game.state  = pixel_art_buffer(game.gl);
    game.temp   = pixel_art_buffer(game.gl);

    // Initialize memory. We'll need to maintain a local "texture shadow"
    // For the height map we'll also keep that CPU-side
    game.height = new Uint8Array(game.w*game.h);
    for (var i=0; i<game.w*game.h; i++) game.height[i]=Math.floor(Math.random()*5);
    function height_to_map(h) { 
        h = Math.max(0,Math.min(4,Math.floor(h)));
        switch (h) {
            case 0: return [BOX0 ,BOX0 ,BOX0 ,BOX0 ];
            case 1: return [BOX0 ,BOX0 ,BOX0 ,EMPTY];
            case 2: return [BOX0 ,BOX0 ,EMPTY,EMPTY];
            case 3: return [BOX0 ,EMPTY,EMPTY,EMPTY];
            case 4: return [EMPTY,EMPTY,EMPTY,EMPTY];
            /*
            case 0: return [EMPTY,EMPTY,EMPTY,BOX0 ];
            case 1: return [EMPTY,EMPTY,BOX0 ,EMPTY];
            case 2: return [EMPTY,BOX0 ,EMPTY,EMPTY];
            case 3: return [BOX0 ,EMPTY,EMPTY,EMPTY];
            case 4: return [EMPTY,EMPTY,EMPTY,EMPTY];
            */
        }
    }
    game.data   = new Uint8Array(game.w*game.h*4);
    for (var i=0; i<game.w*game.h; i++) {
        var v = height_to_map(game.height[i])
        game.data[i*4+0]=v[0];
        game.data[i*4+1]=v[1];
        game.data[i*4+2]=v[2];
        game.data[i*4+3]=v[3];
    }
    var gl = game.gl;
    gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL,false)
    gl.pixelStorei(gl.UNPACK_PREMULTIPLY_ALPHA_WEBGL,false)
    gl.bindTexture(gl.TEXTURE_2D,game.state.texture);
    gl.texSubImage2D(gl.TEXTURE_2D,0,0,0,game.w,game.h,gl.RGBA,gl.UNSIGNED_BYTE,game.data);
    game.boxes({game_state:game.state},game.tiles);

    // Tool actions
    game.tool = SELECT;
    game.set_tool=(i)=>{
        console.log(i);
        game.tool = i;
    }
    game.set_tile=(p,t,layers)=>{
        var gl = game.gl;
        var i  = (p.x+game.w*p.y)*4;
        layers = layers || [0,1,2,3]
        layers.forEach((j)=>{game.data[i+j]=t});
        var c  = game.data.subarray(i,i+5);
        gl.bindTexture  (gl.TEXTURE_2D,game.state.texture);
        gl.texSubImage2D(gl.TEXTURE_2D,0,p.x,p.y,1,1,gl.RGBA,gl.UNSIGNED_BYTE,c);
        gl.bindTexture  (gl.TEXTURE_2D,null);
    }
    game.set_height=(p,h)=>{
        //game.height = h;
        var i = p.x+game.w*p.y;
        game.height[i] = h;
        console.log(p,game.height[i]);
        var v = height_to_map(h);
        var c  = game.data.subarray(i,i+5);
        c[0]=v[0];
        c[1]=v[1];
        c[2]=v[2];
        c[3]=v[3];

        gl.bindTexture  (gl.TEXTURE_2D,game.state.texture);
        gl.texSubImage2D(gl.TEXTURE_2D,0,p.x,p.y,1,1,gl.RGBA,gl.UNSIGNED_BYTE,c);
        gl.bindTexture  (gl.TEXTURE_2D,null);
    };

    game.update_focus=(gx,gy)=>{
        var w = game.canvas.width;
        var h = game.canvas.height;
        var xpad = w/2/game.scale;
        gx = Math.min(game.wpx-xpad,Math.max(xpad,gx));      
        var ypad = h/2/game.scale;
        gy = Math.min(game.hpx-ypad,Math.max(ypad,gy)); 
        if (game.hpx*game.scale<=h) gy=game.hpx/2;
        if (game.wpx*game.scale<=w) gx=game.wpx/2;
        game.focus_x = gx;
        game.focus_y = gy;
    }

    game.update_scale=(s,e)=>{
        var w  = game.canvas.width;
        var h  = game.canvas.height;
        var s0 = game.scale;
        s = s|| game.scale;
        var s1 = Math.min(max_scale,Math.max(min_scale,s));
        game.scale = s1;
        e = e || {x:w/2,y:h/2};
        game.update_focus(
            game.focus_x+(e.x-w/2)*(1/s0-1/s1),
            game.focus_y-(e.y-h/2)*(1/s0-1/s1));
    }

    // Event listeners

    // Click applies current tool
    game.tool_action=(e)=>{
        if (game.tool==SELECT) {
            if (game.downp) {
                var r = window.devicePixelRatio;
                game.update_focus(game.downp.gx-(e.x-game.downp.mx)*r/game.scale,
                                  game.downp.gy+(e.y-game.downp.my)/game.scale);
            }
            return;
        }
        var p = mouse_to_game_point(game,e);
        var q = {x:Math.floor(p.x/tile_w),y:Math.floor(p.y/tile_h)};
        var pp = [];
        if (game.isdown&&game.downp) {
            //Bresenham's line algorithm
            var x0=game.downp.qx;
            var y0=game.downp.qy;
            var x1 =q.x;
            var y1 =q.y;
            var dx = Math.abs(x1-x0);
            var dy = -Math.abs(y1-y0);
            var sx = x0<x1?1:-1;
            var sy = y0<y1?1:-1;
            var de = Math.abs(dy/dx);
            var er = dx+dy;
            var y  = y0;
            while (true) {
                var pr = pp[pp.length-1];
                if (pr&&pr.x!=x0&&pr.y!=y0) pp.push({x:x0,y:pr.y});
                pp.push({x:x0,y:y0});
                if (x0==x1&&y0==y1) break;
                var e2 = 2*er;
                if (e2>=dy) {er+=dy;x0+=sx;}
                if (e2<=dx) {er+=dx;y0+=sy;}
            }
        } else pp=[q];
        /*
        var tile, layers;
        switch (game.tool) {
            case DELETE: tile=EMPTY; layers=[0,1,2,3];break;
            case BOX0:   tile=BOX0;  layers=[2];      break;
            case BOX1:   tile=BOX1;  layers=[1];      break;
            case BOX2:   tile=BOX2;  layers=[0];      break;
            case BOX3:   tile=BOX3;  layers=[3];      break;
            case DELETE: game.set_height(p);
        }
        pp.forEach((p)=>{game.set_tile(p,tile,layers)});
        */

        var h = 0;
        switch (game.tool) {
            case DELETE: h=0; break;
            case BOX0: h=1; break;
            case BOX1: h=2; break;
            case BOX2: h=3; break;
            case BOX3: h=4; break;
        }
        pp.forEach((p)=>{game.set_height(p,h)});

        game.boxes({game_state:game.state},game.tiles);
        game.render();
    };
    game.canvas.addEventListener("click",game.tool_action);

    // Moving either drags tool or pans view
    game.update_mouse_highlight=(e)=>{
        var p = mouse_to_game_point(game,e);
        game.select=[Math.floor(p.x/tile_w),Math.floor(p.y/tile_h)];
        game.render();
    };

    game.canvas.addEventListener("mousemove", function(e) {
        var button_state = e.buttons||e.which
        if (game.isdown && !(button_state&1)) console.log("abnormal end of dragging");
        game.isdown &= !!(button_state&1);
        if (game.isdown) {
            game.tool_action(e);
            var p = mouse_to_game_point(game,e);
            var q = {x:Math.floor(p.x/tile_w),y:Math.floor(p.y/tile_h)};
            game.downp = {mx:e.x,my:e.y,gx:game.focus_x,gy:game.focus_y,px:p.x,py:p.y,qx:q.x,qy:q.y};
            game.canvas.style.cursor="grabbing";
        } else {
            game.downp = null;
            game.canvas.style.cursor="default";
        }
        game.update_mouse_highlight(e);
    });

    // Drag handlers
    game.isdown=false;
    game.downp ={mx:0,my:0,gx:0,gy:0};
    
    game.canvas.addEventListener("mousedown", function(e) {
        var p = mouse_to_game_point(game,e);
        var q = {x:Math.floor(p.x/tile_w),y:Math.floor(p.y/tile_h)};
        game.downp  = {mx:e.x,my:e.y,gx:game.focus_x,gy:game.focus_y,px:p.x,py:p.y,qx:q.x,qy:q.y};
        game.isdown = true;
        game.canvas.style.cursor="grabbing";
    });
    
    game.canvas.addEventListener("mouseup", function(e) {
        game.isdown = false;
        game.downp  = null;
        game.canvas.style.cursor="default";
    });

    // Zoom w. scroll wheel
    game.canvas.addEventListener("wheel", function(e) {
        game.update_scale(game.scale/Math.exp(Math.sign(e.deltaY)*0.05),e);
        game.render();
    });

    game.noselect=(e)=>{
        game.select=[-1,1];
        if (game.tool!=SELECT) {game.isdown=false;game.downp=false;}
        game.render();
    }
    game.canvas.addEventListener("mouseleave",game.noselect);
    game.canvas.addEventListener("mouseout"  ,game.noselect);

    // Hilight buttons when corresponding key pressed
    function keybutton(t) {
        var button = controls.buttons[t];
        if (button) {
            controls.select = [button.x,button.y];
            controls.render()
        }
    }

    // Key-driven actions
    game.left   =()=>{
        if (game.tool!=0) {
            game.select = [Math.max(0,game.select[0]), game.select[1]]
        }
        game.update_focus(game.focus_x-key_pan/game.scale,game.focus_y);
        game.render(); 
        keybutton(LEFT);
    }
    game.right  =()=>{
        game.update_focus(game.focus_x+key_pan/game.scale,game.focus_y);
        game.render(); 
        keybutton(RIGHT);
    }
    game.down   =()=>{
        game.update_focus(game.focus_x,game.focus_y-key_pan/game.scale);
        game.render(); 
        keybutton(DOWN);
    }
    game.up     =()=>{
        game.update_focus(game.focus_x,game.focus_y+key_pan/game.scale);
        game.render(); 
        keybutton(UP);
    }
    game.zoomin =()=>{
        game.update_scale(game.scale/key_zoom);
        game.render();
        keybutton(IN);
    }
    game.zoomout=()=>{
        game.update_scale(game.scale*key_zoom);
        game.render();
        keybutton(OUT);
    }

    game.resize = ()=>{
        var c = game.canvas;
        var w = Math.round(c.clientWidth *window.devicePixelRatio);
        var h = Math.round(c.clientHeight*window.devicePixelRatio);
        if (c.width!=w||c.height!=h) {
            c.width =w; 
            c.height=h;
            game.update_scale();
            game.render();
        }
    }
    window.addEventListener("resize",game.resize);

    // Add keyboard navigation
    window.addEventListener("keydown",(e)=>{
        switch (e.key) {
            case "ArrowLeft" : case "a": case "A": case "4":
            game.left();
            break;
            case "ArrowRight": case "d": case "D": case "6":
            game.right();
            break;
            case "ArrowDown" : case "s": case "S": case "2":
            game.down();
            break;
            case "ArrowUp"   : case "w": case "W": case "8": 
            game.up();
            break;
            case "PageUp"    : case "q": case "Q": case "9": case "-": case "_":
            game.zoomin(); 
            break;
            case "PageDown"  : case "e": case "E": case "3": case "+": case "=":
            game.zoomout();
            break;
        }
    });

    return game
}

/** 
 * Main script that will run when the website loads
 */
function main()
{
    game     = init_game();
    console.log("initialized game");
    controls = init_controls();
    console.log("initialized controls");
    game.resize();
    game.render();
    controls.resize();
    controls.render();
}


/**
 * Load tiles image from base64 string.
 * We wait until the image loads before initializing the WebGL environment.
 * We achieve this by calling main() from the textures "onload" callback.
 */
function load_textures() {
    tiles = new Image();
    tiles.crossOrigin = "anonymous";
    tiles.onload = main;
    tiles.src = base64_textures.city_translucent;
    console.log("loaded texture");
}
</script>
</body>
</htlm>