Make a finish line for your race.
Click the paintbrush icon to draw a new sprite:
Click on the line tool. Select the color you want from the color palette.
Tip: Hold down the Shift key while drawing the line to make it straight.
You can make a thicker line using the 'Line width' slider:
Now you can drag your finish line to where you want it on the Stage.
Tip: You can use the eraser tool to shorten the line so it fits on the track.
Do something if you reach the finish line