Percy the Potty Pigeon: Routine at 25531

25531: Print HUD Header

Used by the routine at Draw_Room_Rows_Loop. Prints the heads-up display header showing Energy, Lives and Score, then applies random colours to the bottom two rows of the screen attributes to create a colourful ground strip.
Print_HUD_Header	25531	LD A,1	Write 1 to *Screen_Initialised_Flag.
	25533	LD (24481),A	Write 1 to *Screen_Initialised_Flag.
Print the HUD string to the upper screen.
	25536	CALL 5633	Call CHAN_OPEN to open channel 2 (upper screen).
	25539	LD HL,25577	Point HL at Messaging_Header.
	25542	LD B,79	Set a counter in B for the length of the string (79 characters).
	25544	CALL PrintString	Call PrintString.
This entry point is used by the routine at Draw_Room_Rows_Loop. Apply pseudo-random colours to the bottom two rows of screen attributes to create a colourful ground strip. Uses the Memory Refresh Register as a seed to pick unpredictable colour values.
Colour_Ground_Strip	25547	LD A,R	Load the Memory Refresh Register into E as a pointer offset.
	25549	LD E,A
	25550	LD D,0	Set D to 0 so DE is an offset into low memory.
	25552	LD B,32	Set a counter in B for 32 attribute cells.
	25554	LD HL,23232	Point HL at 23232 (start of the bottom two attribute rows).
Colour_Ground_Loop	25557	LD A,(DE)	Fetch a pseudo-random byte from *DE.
	25558	AND %00000111	Keep only bits 0-2 (INK colour).
	25560	INC DE	Advance the source pointer.
	25561	CP 3	Jump back to Colour_Ground_Loop if the colour is less than 3 (reject dark colours to keep the ground strip bright).
	25563	JR C,Colour_Ground_Loop
	25565	PUSH DE	Stash the source pointer on the stack.
	25566	LD E,A	Copy the chosen colour into E.
	25567	LD A,(HL)	Fetch the current attribute byte from *HL.
	25568	AND %11110111	Mask off the existing INK bits (keep PAPER, BRIGHT, FLASH).
	25570	OR E	OR in the new INK colour from E.
	25571	LD (HL),E	Write the updated attribute byte to *HL.
	25572	POP DE	Restore the source pointer from the stack.
	25573	INC HL	Advance to the next attribute cell.
	25574	DJNZ Colour_Ground_Loop	Decrease the counter and loop back to Colour_Ground_Loop until all 32 cells are coloured.
	25576	RET	Return.