The car should steer straight until you hit a pothole, another car, or a enemy bullet. For the counter, I made 6 columns of sprites 0-9 and applied a sprite mask the height of one digit. Then I modified their position based on the time playing the level with a mod (%) to wrap them around. Very similar to how scrolling repeating backgrounds are often done, but vertically.
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Thanks for the explanation. I guess I didn't explain my criticism all that well. When you're shooting you move the mouse over the enemy car, if you then stop shooting the car will suddenly change direction (since the mouse is not overhead). So, the player has to return the mouse to the car before they can stop shooting. Maybe you can solve this by resetting the mouse cursor to the position of the car. You will need to do some trickery for that, since operating systems don't allow a program to move the cursor.