| Routines

F905: Collect the identifier for the next lesson

Used by the routine at 66E6. Returns with A holding the identifier (0xE0-0xFF) for the next lesson. If the next lesson is PLAYTIME, one of the 'special' PLAYTIMEs (0xF3, 0xF4 or 0xF5) may be chosen in place of the main timetable entry.
Input
E | Lesson number (0x00-0x3F)
F905 | LD D,$FE | Pick up the lesson identifier (0xE0-0xFF) from the main timetable
F907 | LD A,(DE)
F908 | CP $F3 | Is it PLAYTIME (0xF3-0xFF)?
F90A | RET C | Return if not
F90B | LD A,($7FEA) | 7FEA holds the game mode indicator
F90E | AND A | Set the zero flag if we're in demo mode
F90F | LD A,(DE) | Restore the lesson identifier to A and return if we're in demo mode
F910 | RET Z
F911 | CALL $61A1 | A=random number
F914 | JP $6E33 | Select a 'special' PLAYTIME occasionally