# Using the ball angle block

The ‘ball angle’ block (Sensors) is used to get a measurement of angle, between -180 and +180. If the ball is on the left of the robot, the number is negative. If the ball is on the right, the ball is positive.

## Rotate to face the ball

Let’s write a program that will rotate the robot to face the ball.

• We need an ‘if’ block (Control) - because the robot needs to make a decision.
• We also need a ‘comparison’ block (Operators) - because we need to check that the ball distance is greater than 100.

We have three conditions:

• If the ball is to the left (ball angle < -20), then the robot should rotate left.
• Otherwise, if the ball is to the right (ball angle > 20), then the robot should rotate right.
• Otherwise, the robot should stop.

We’re using -20 and 20 degrees because the robot can’t stop instantly.

Let’s start with the if. Here, we drag the if and comparison blocks, and we can also press the + to get the ‘else if’ section. Now we just need to add the motor movement.

• Rotate left means the left wheel needs to go backwards (negative) and the right wheel goes forwards (positive).
• The opposite for rotating right. 