The breast cancer features exercise is only 'loosely' interactive. It encourages users to manipulate the code, but has no actual requirements for this and can run front-to-back without modification. Therefore, this exercise does not currently pass Principle 2 (of being interactive).
To improve it, there should be more explicit "stop points" where users are prompted to modify the code. For example, this could describe functions that could be used, but which aren't yet implemented - and invite the user to implement them and play around.
The breast cancer features exercise is only 'loosely' interactive. It encourages users to manipulate the code, but has no actual requirements for this and can run front-to-back without modification. Therefore, this exercise does not currently pass Principle 2 (of being interactive).
To improve it, there should be more explicit "stop points" where users are prompted to modify the code. For example, this could describe functions that could be used, but which aren't yet implemented - and invite the user to implement them and play around.