Custom 3-Panel Accordion

Card 1 body content.

When Card 1 and Card 2 are expanded, Card 3 is collapsed. If you collapse Card 2 from this state, Card 1 grows to fill the space.

Card 2 body content.

Card 1 + 2 expanded ⇒ Card 3 collapsed.
Card 2 + 3 expanded ⇒ Card 1 collapsed.
From (1 + 2 open), clicking Card 2 collapses Card 2, Card 1 fills space. Clicking Card 2 again (while 1 is expanded) restores the previous state.
From (2 + 3 open), clicking Card 2 collapses Card 2, Card 3 fills space. Clicking Card 2 again (while 3 is expanded) restores the previous state.

Card 3 body content.

Clicking Card 3 header collapses Card 1, keeps Card 2 as-is, and expands Card 3 from the bottom.