Distinguishing intervals which are close together, like semitone and tone (a.k.a. whole step and half step / major and minor seconds) is a sticking point for many students as they learn interval recognition.
The RelativePitch app begins with these intervals and while the lesson sequence works well for many students, in reality every musician is different and so it won’t always be a smooth learning progression. This is why the “Custom Mode” is always available, so you can adjust the sequence to help you keep progressing.
So when you get