Before reading any further, how would you make sure a fish is attracted to food? What information do you need?

How would you make sure fish are scared away by ripples? What information do you need?

Fill out calculateFood. It should:

1. Use delegate.foodLocation() to get a CGPoint?. This value is nil if there is no food on the screen and it has a value if there is food on the screen.
2. If there is food, use the distanceTo method to check if it is less than foodVisibleDistance away from self.position. You can calculate the distance with something like self.position.distanceTo(foodLocation). This assumes that the return value from the delegate has been unwrapped and binded to foodLocation.
3. If the distance is less than foodVisibleDistance, return a vector to the food's location divided by foodWeight. If there is no food or it is too far away, return CGPoint(x: 0, y: 0).

Update updateVelocity to use this new rule. updateVelocity should:

1. Call calculateFood and save it to a variable.
2. Reassign the velocity instance variable to be the sum of the previous velocity, previous rules, and the newly calculated food.
3. Make sure there is a call to clampVelocity after you update the velocity instance variable.

Run the app and check it out! Try tapping to drop some food. Do the fish swarm around it?

Fill out calculateRipple. It should:

1. Use delegate.rippleLocation() to get a CGPoint?. This value is nil if there is no ripple on the screen and it has a value if there is a ripple on the screen.
2. If there is a ripple, use the distanceTo method to check if it is less than rippleVisibleDistance away from self.position. You can calculate the distance with something like self.position.distanceTo(rippleLocation). This assumes that the return value from the delegate has been unwrapped and binded to rippleLocation.
3. If the distance is less than rippleVisibleDistance, return a vector pointing away from the ripple's location divided by rippleWeight. If there is no ripple or it is too far away, return CGPoint(x: 0, y: 0).

Update updateVelocity to use this new rule. updateVelocity should:

1. Call calculateRipple and save it to a variable.
2. Reassign the velocity instance variable to be the sum of the previous velocity, previous rules, and the newly calculated ripple.
3. Make sure there is a call to clampVelocity after you update the velocity instance variable.

Run the app and check it out! Try double-tapping to make a ripple. Do the fish scatter away?