Pentagram: Routine at B4E0

Used by the routine at OBJECT_DONE.

Called once a turn by the main loop (OBJECT_DONE). Half-rows $7F and $FE are read together, so bit 0 is SPACE or CAPS SHIFT and bits 1-4 are the other eight keys of the two rows; the pause needs bit 0 and none of the others, so no key that plays the game can start one. The game beeps (PAUSE_BEEP), waits for the key to be let go, then for a press and a release, and beeps again.

While it waits, interrupts are on: IY is set to the ROM's system variables and EI lets the ROM's frame interrupt run, the only place the game allows it. DI turns them off again before the game goes on. IY is left pointing at the system variables; nothing that follows expects it to hold anything else.

Used by the routine at OBJECT_DONE. Called once a turn by the main loop (OBJECT_DONE). Half-rows $7F and $FE are read together, so bit 0 is SPACE or CAPS SHIFT and bits 1-4 are the other eight keys of the two rows; the pause needs bit 0 and none of the others, so no key that plays the game can start one. The game beeps (PAUSE_BEEP), waits for the key to be let go, then for a press and a release, and beeps again. While it waits, interrupts are on: IY is set to the ROM's system variables and EI lets the ROM's frame interrupt run, the only place the game allows it. DI turns them off again before the game goes on. IY is left pointing at the system variables; nothing that follows expects it to hold anything else.
PAUSE	B4E0	LD A,$7E	not SPACE or CAPS SHIFT: no pause
	B4E2	CALL READ_KEYS
	B4E5	BIT 0,A
	B4E7	RET Z
	B4E8	AND $1E	another key with it: no pause
	B4EA	RET NZ	another key with it: no pause
	B4EB	CALL PAUSE_BEEP	a beep
PAUSE_0	B4EE	LD A,$7E	wait for it to be let go
	B4F0	CALL READ_KEYS
	B4F3	BIT 0,A
	B4F5	JR NZ,PAUSE_0
	B4F7	LD IY,$5C3A	the ROM's interrupt routine may run while the game waits
	B4FB	EI	the ROM's interrupt routine may run while the game waits
PAUSE_1	B4FC	LD A,$7E	wait for a press
	B4FE	CALL READ_KEYS
	B501	BIT 0,A
	B503	JR Z,PAUSE_1
PAUSE_2	B505	LD A,$7E	and for it to be let go
	B507	CALL READ_KEYS
	B50A	BIT 0,A
	B50C	JR NZ,PAUSE_2
	B50E	DI	interrupts off again; a beep
	B50F	CALL PAUSE_BEEP
	B512	RET