Bubbler: Routine at CA17

CA17: Shift View Left Nibble

Shifts the screen buffer to the left by four pixels, by rotating the nibbles of each row.
ShiftViewLeftNibble	CA17	LD B,$80	Set the row count to 80.
	CA19	LD HL,$F1BA	Point HL at the last byte of the screen buffer.
	CA1C	XOR A	Clear the nibble shifted in from the right.
ShiftViewLeftNibble_Loop	CA1D	RLD	Shift the row four pixels to the left.
	CA1F	DEC HL
	CA20	RLD
	CA22	DEC HL
	CA23	RLD
	CA25	DEC HL
	CA26	RLD
	CA28	DEC HL
	CA29	RLD
	CA2B	DEC HL
	CA2C	RLD
	CA2E	DEC HL
	CA2F	RLD
	CA31	DEC HL
	CA32	RLD
	CA34	DEC HL
	CA35	RLD
	CA37	DEC HL
	CA38	RLD
	CA3A	DEC HL
	CA3B	RLD
	CA3D	DEC HL
	CA3E	RLD
	CA40	DEC HL
	CA41	RLD
	CA43	DEC HL
	CA44	RLD
	CA46	DEC HL
	CA47	RLD
	CA49	DEC HL
	CA4A	RLD
	CA4C	DEC HL
	CA4D	RLD
	CA4F	DEC HL
	CA50	RLD
	CA52	DEC HL
	CA53	RLD
	CA55	DEC HL
	CA56	RLD
	CA58	DEC HL
	CA59	RLD
	CA5B	DEC HL
	CA5C	RLD
	CA5E	DEC HL
	CA5F	RLD
	CA61	DEC HL
	CA62	RLD
	CA64	DEC HL
	CA65	XOR A	Discard the nibble that fell off the left of the row.
	CA66	DJNZ ShiftViewLeftNibble_Loop	Decrease the row count and jump back until every row of the buffer has been shifted.
	CA68	RET	Return.