If you remember, to turn the car, you rotate the iPad left and right. To speed up, you tilt it forward (away from you). To slow down, you tilt it backwards (towards you). Sounds simple, no?
Well, after much testing, game players could not turn to the left and drive fast. It required twisting their hands to hold the iPad in a very uncomfortable manner. Back to the drawing board.
When holding the iPad or iPhone, your thumbs tend to hover around the center of the left and right edges of the screen. To make it easy, we let you speed up the car by tapping your right thumb on the right edge of the screen, and to slow down by tapping your left thumb on the left edge.
We tested it with children, and instead of tapping, then just pressed their thumb and held it for a few seconds. So we changed the game to respond to press-and-hold your left and right thumb. And we tested it again. This time, the children tapped their thumbs instead of tapping their thumbs.
Testing the game showed this type of contrary behavior quite often. For example, when children who have never steered a car are asked to turn the iPad left and right, they keep the iPad flat (parallel to the floor) and tilt up the left or right side. Adults, who have steered a car, turn the iPad like a steering wheel, keeping the iPad screen facing their body.
In each of these cases, we adjusted the app to work in all scenarios. Similarly, people rotate or turn the iPad different amounts to complete a turn. Some will turn it 90 degrees, some 60 degrees, some 120 degrees. The app learns about the game player and self-adjusts to accommodate what the game player means. During the tutorial, it learns what the game player will do for a “maximum turn”, and then computes what percent of a “maximum turn” when she is doing when turning the car, and then turns the car appropriately.
We experimented with another variant of the game – steering and driving like the real world. To understand the difference, look at these two pictures.
In the first, when you rotate the iPad, the car rotates, and when you straighten the iPad, the car goes straight again.
In the real world, when you start turning the wheel, the car turns to the right until the car is 90 degrees from its original position. Then you straighten out the wheel, but the car continues at 90 degrees from its initial direction. Likewise for a turn to the left:
Game players found real world steering was just too difficult, and they couldn’t figure out how much to turn to keep the car away from the fence.