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 Math.floor( (frame % this.cols) * this.tilew + this.sx);
      },
  
      fy: function(frame) {
        return Math.floor( 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
    //    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||{});
          this.p.id = this.p.id || _.uniqueId();
          this.stepData = {};
  
          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;
            }
          }
  
        },
  
        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(this.asset(), Math.floor(p.x), Math.floor(p.y));
          }
          this.trigger('draw',ctx);
        },
  
        step: function(dt) {
          this.stepData.dt = dt;
          this.trigger('step',this.stepData);
        }
      });
        
  
    Q.MovingSprite = Q.Sprite.extend({
      init: function(props) {
        this._super(_({
          vx: 0,
          vy: 0,
          ax: 0,
          ay: 0
          }).extend(props||{}));
      },
  
      update: function(dt) {
        this._super();
        var v = this.v;
  
        p.vx += p.ax * dt;
        p.vy += p.ay * dt;
  
        p.x += p.vx * dt;
        p.y += p.vy * dt;
      }
     });
  
  }