Sometimes when your scene gets a little bit longer you may want to select just part of it to playback. To do this just pause on the first frame that you want to include in the playback and click on the button at the left of the slider under the image window. Then pause on the last frame that you want to include in the playback and click on the button at the right end of the slider. You’ll notice a blue line appear between the two points you selected. That’s what will be included when you played the scene.