We are given a .NET executable for this challenge. We run it and we have a piano that plays notes when we hit the keys.
We can open it in dnSpy to decompile and debug. We can see the key_click function looks interesting because it is tracking a state if keys are pressed in a certain order.
The keys are numbered from left to right starting at 0 for the white keys and the same for the black keys. If we press the keys in the correct order do_a_thing() is called.
This function plays a funny David Bowie video while the key scrolls in ascii art behind.