Routines| H | Number of character we're interested in the visibility of |
| 27886 | 2E02 | LD L,2 | |
| 27888 | 56 | LD D,(HL) | Pick up the character's y-coordinate in D |
| 27889 | 2D | DEC L | |
| 27890 | 5E | LD E,(HL) | Pick up the character's x-coordinate in E |
| 27891 | 0E00 | LD C,0 | Prepare lower limit of 0 in case E<10 |
| 27893 | 7B | LD A,E | |
| 27894 | D60A | SUB 10 | |
| 27896 | 3801 | JR C,27899 | |
| 27898 | 4F | LD C,A | C=lower limit of range |
| 27899 | C614 | ADD A,20 | |
| 27901 | 47 | LD B,A | B=upper limit of range |
| 27902 | C9 | RET |