Quintus.Sprites = function(Q) {
   
    // Create a new sprite sheet
    // Options:
    //  tilew - tile width
    //  tileh - tile height
    //  w     - width of the sprite block
    //  h     - height of the sprite block
    //  sx    - start x
    //  sy    - start y
    //  cols  - number of columns per row
    Q.SpriteSheet = Class.extend({
      init: function(name, asset,options) {
        _.extend(this,{
          name: name,
          asset: asset,
          w: Q.asset(asset).width,
          h: Q.asset(asset).height,
          tilew: 64,
          tileh: 64,
          sx: 0,
          sy: 0
          },options);
        this.cols = this.cols || 
                    Math.floor(this.w / this.tilew);
      },
  
      fx: function(frame) {
        return (frame % this.cols) * this.tilew + this.sx;
      },
  
      fy: function(frame) {
        return Math.floor(frame / this.cols) * this.tileh + this.sy;
      },
  
      draw: function(ctx, x, y, frame) {
        if(!ctx) { ctx = Q.ctx; }
        ctx.drawImage(Q.asset(this.asset),
                      this.fx(frame),this.fy(frame),
                      this.tilew, this.tileh,
                      Math.floor(x),Math.floor(y),
                      this.tilew, this.tileh);
  
      }
  
    });
  
    Q.sheets = {};
    Q.sheet = function(name,asset,options) {
      if(asset) {
        Q.sheets[name] = new Q.SpriteSheet(name,asset,options);
      } else {
        return Q.sheets[name];
      }
    };
  
    Q.compileSheets = function(imageAsset,spriteDataAsset) {
      var data = Q.asset(spriteDataAsset);
      _(data).each(function(spriteData,name) {
        Q.sheet(name,imageAsset,spriteData);
      });
    };
  
  // Properties:
    //    x
    //    y
    //    z - sort order
    //    sheet or asset
    //    frame
    Q.Sprite = Q.GameObject.extend({
      init: function(props) {
        this.p = _({ 
          x: 0,
          y: 0,
          z: 0,
          frame: 0,
          type: 0
        }).extend(props||{});
        if((!this.p.w || !this.p.h)) {
          if(this.asset()) {
            this.p.w = this.p.w || this.asset().width;
            this.p.h = this.p.h || this.asset().height;
          } else if(this.sheet()) {
            this.p.w = this.p.w || this.sheet().tilew;
            this.p.h = this.p.h || this.sheet().tileh;
          }
        }
        this.p.id = this.p.id || _.uniqueId();
      },
  
      asset: function() {
        return Q.asset(this.p.asset);
      },
  
      sheet: function() {
        return Q.sheet(this.p.sheet);
      },
  
      draw: function(ctx) {
        if(!ctx) { ctx = Q.ctx; }
        var p = this.p;
        if(p.sheet) {
          this.sheet().draw(ctx, p.x, p.y, p.frame);
        } else if(p.asset) {
          ctx.drawImage(Q.asset(p.asset), 
          Math.floor(p.x), 
          Math.floor(p.y));
        }
        this.trigger('draw',ctx);
      },
  
      step: function(dt) {
        this.trigger('step',dt);
      }
    });
  
    return Q;
  };