code: function executeCommand(command, circles, current, position) {
              var circle = circles[current],
                  transformed = false;
  
              switch (command) {
                  case 'increase-x':
                      circle.x += 10;
                      transformed = true;
                      break;
                  case 'decrease-x':
                      circle.x -= 10;
                      transformed = true;
                      break;
                  case 'increase-y':
                      circle.y += 10;
                      transformed = true;
                      break;
                  case 'decrease-y':
                      circle.y -= 10;
                      transformed = true;
                      break;
                  case 'increase-r':
                      circle.r += 10;
                      transformed = true;
                      break;
                  case 'decrease-r':
                      circle.r -= 10;
                      transformed = true;
                      break;
                  case 'bring-to-front':
                      bringToFront(circles, circle, current);
                      break;
                  case 'send-to-back':
                      sendToBack(circles, circle, current);
                      break;
                  case 'new-circle':
                      newCircle(position, circles, TOOLBAR_HEIGHT);
                      break;
                  case 'random-circle':
                      randomCircle(circles, TOOLBAR_HEIGHT);
                      break;
                  case 'remove-circle':
                      removeCircle(circles, current);
                      break;
                  case 'move':
                      moveCircles(circles, position);
                      break;
                  case 'clear':
                      clear(circles);
                      break;
              }
  
              if (transformed) {
                  circle.x = Math.max(circle.x, 10);
                  circle.y = Math.max(circle.y, 10);
                  circle.r = Math.max(circle.r, 10);
              }
  
              return circles;
          }
docs: <editor-fold desc="Circles & commands">