    ctx.beginPath();
        ctx.arc(a.op.x, a.op.y, a.rad, 0, Math.PI*2, true);
        ctx.fill();
        ctx.stroke();
        
        // draw agents sight
        for(var ei=0,ne=a.eyes.length;ei<ne;ei++) {
          var e = a.eyes[ei];
          var sr = e.sensed_proximity;
          if(e.sensed_type === -1 || e.sensed_type === 0) {
            ctx.strokeStyle = "rgb(200,200,200)"; // wall or nothing
          }
          if(e.sensed_type === 1) { ctx.strokeStyle = "rgb(255,150,150)"; } // apples
   