Quintus.Anim = function(Q) {
    Q._animations = {};
    Q.animations = function(sprite,animations) {
      if(!Q._animations[sprite]) Q._animations[sprite] = {};
      _.extend(Q._animations[sprite],animations);
    };
  
    Q.animation = function(sprite,name) {
      return Q._animations[sprite] && Q._animations[sprite][name];
    };
  
    Q.register('animation',{
      added: function() {
        var p = this.entity.p;
        p.animation = null;
        p.animationPriority = -1;
        p.animationFrame = 0;
        p.animationTime = 0;
        this.entity.bind("step",this,"step");
      },
      extend: {
        play: function(name,priority) {
          this.animation.play(name,priority);
        }
      },
      step: function(dt) {
        var entity = this.entity,
            p = entity.p;
        if(p.animation) {
          var anim = Q.animation(p.sprite,p.animation),
              rate = anim.rate || p.rate,
              stepped = 0;
          p.animationTime += dt;
          if(p.animationChanged) {
            p.animationChanged = false;
          } else { 
            p.animationTime += dt;
            if(p.animationTime > rate) {
              stepped = Math.floor(p.animationTime / rate);
              p.animationTime -= stepped * rate;
              p.animationFrame += stepped;
            }
          }
          if(stepped > 0) {
            if(p.animationFrame >= anim.frames.length) {
              if(anim.loop === false || anim.next) {
                p.animationFrame = anim.frames.length - 1;
                entity.trigger('animEnd');
                entity.trigger('animEnd.' + p.animation);
                p.animation = null;
                p.animationPriority = -1;
                if(anim.trigger) {  
                  entity.trigger(anim.trigger,anim.triggerData) 
                }
                if(anim.next) { this.play(anim.next,anim.nextPriority); }
                return;
              } else {
                entity.trigger('animLoop');
                entity.trigger('animLoop.' + p.animation);
                p.animationFrame = p.animationFrame % anim.frames.length;
              }
            }
            entity.trigger("animFrame");
          }
          p.sheet = anim.sheet || p.sheet;
          p.frame = anim.frames[p.animationFrame];
        }
      },
  
      play: function(name,priority) {
        var entity = this.entity,
            p = entity.p;
        priority = priority || 0;
        if(name != p.animation && priority >= p.animationPriority) {
          p.animation = name;
          p.animationChanged = true;
          p.animationTime = 0;
          p.animationFrame = 0;
          p.animationPriority = priority;
          entity.trigger('anim');
          entity.trigger('anim.' + p.animation);
        }
      }
    
    });
  
    Q.register('viewport',{
      added: function() {
        this.entity.bind('predraw',this,'predraw');
        this.entity.bind('draw',this,'postdraw');
        this.x = 0,
        this.y = 0;
        this.centerX = Q.width/2;
        this.centerY = Q.height/2;
        this.scale = 1;
      },
  
      extend: {
        follow: function(sprite) {
          this.unbind('step',this.viewport);
          this.viewport.following = sprite;
          this.bind('step',this.viewport,'follow');
          this.viewport.follow();
        },
  
        unfollow: function() {
          this.unbind('step',this.viewport);
        },
  
        centerOn: function(x,y) {
          this.viewport.centerOn(x,y);
        }
      },
  
      follow: function() {
        this.centerOn(this.following.p.x + this.following.p.w/2,
                      this.following.p.y + this.following.p.h/2);
      },
  
      centerOn: function(x,y) {
        this.centerX = x;
        this.centerY = y;
        this.x = this.centerX - Q.width / 2 / this.scale;
        this.y = this.centerY - Q.height / 2 / this.scale;
      },
  
      predraw: function() {
        Q.ctx.save();
        Q.ctx.translate(Q.width/2,Q.height/2);
        Q.ctx.scale(this.scale,this.scale);
        Q.ctx.translate(-this.centerX, -this.centerY);
      },
  
      postdraw: function() {
        Q.ctx.restore();
      }
    });
  
    Q.Repeater = Q.Sprite.extend({
      init: function(props) {
        this._super(_(props).defaults({
          speedX: 1,
          speedY: 1,
          repeatY: true,
          repeatX: true
        }));
        this.p.repeatW = this.p.repeatW || this.p.w;
        this.p.repeatH = this.p.repeatH || this.p.h;
      },
  
      draw: function(ctx) {
        var p = this.p,
            asset = this.asset(),
            sheet = this.sheet(),
            scale = this.parent.viewport.scale,
            viewX = this.parent.viewport.x,
            viewY = this.parent.viewport.y,
            offsetX = p.x + viewX * this.p.speedX,
            offsetY = p.y + viewY * this.p.speedY,
            curX, curY, startX;
        if(p.repeatX) {
          curX = Math.floor(-offsetX % p.repeatW);
          if(curX > 0) { curX -= p.repeatW; }
        } else {
          curX = p.x - viewX;
        }
        if(p.repeatY) {
          curY = Math.floor(-offsetY % p.repeatH);
          if(curY > 0) { curY -= p.repeatH; }
        } else {
          curY = p.y - viewY;
        }
        startX = curX;
        while(curY < Q.height / scale) {
          curX = startX;
          while(curX < Q.width / scale) {
            if(sheet) {
              sheet.draw(ctx,curX + viewX, curY + viewY,p.frame);
            } else {
              ctx.drawImage(asset,curX + viewX, curY + viewY);
            }
            curX += p.repeatW;
            if(!p.repeatX) { break; }
          }
          curY += p.repeatH;
          if(!p.repeatY) { break; }
        }
      }
    });
  
  };