The SPDT switches should realistically be mechanically connected. You will want to toggle both switches in the same direction.
Doing so will cause the positive and negative bus to switch. Any feedback or optimizations would be appreciated. I understand this circuit may not have any practical use. I'm simply a first year electronics technician student and find this fun to fool around with.
EDIT: Made a revised version operated by a single switch and a set of relays.
