This keymap is for operation verification.
,-------------.
| 1 | 2 |
| | |
|------+------|
| 4 | 3 |
| | |
|------+------|
| 5 | 6 |
| | |
|------+------|
| 7 | 8 |
| | |
|------+------|
| 9 | a |
| | |
|------+------|
| b | c |
| | |
`-------------'