+-----------+ S P A C E +-----------+
| S P A C E | -----------> | S P A C Y |
+-----------+ +-----------+
+-----------+ A B C D +-----------+
| A B C | -----------> | X Z Y |
+-----------+ +-----------+
+-----------+ S P A C E +-----------+
| S P A C E | -----------> | S P A C Y |
+-----------+ +-----------+
+-----------+ A B C D +-----------+
| A B C | -----------> | X Z Y |
+-----------+ +-----------+