Fix FLASH setting

FLASH 8 was not being set (transparent mode).
Also FLASH 0 is now 0 and any other value is FLASH 1.

Author: boriel

library-asm/flash.asm

@@ -5,21 +5,39 @@
 
 FLASH:
 	ld de, ATTR_P
+
+    PROC
+    LOCAL IS_TR
+    LOCAL IS_ZERO
+
 __SET_FLASH:
 	; Another entry. This will set the flash flag at location pointer by DE
-	and 1	; # Convert to 0/1
+	cp 8
+	jr z, IS_TR
+
+	; # Convert to 0/1
+	or a
+	jr z, IS_ZERO
+	ld a, 0x80
 
-	rrca
+IS_ZERO:
 	ld b, a	; Saves the color
 	ld a, (de)
 	and 07Fh ; Clears previous value
 	or b
 	ld (de), a
 	ret
 
+IS_TR:  ; transparent
+	inc de ; Points DE to MASK_T or MASK_P
+	ld a, (de)
+	or 0x80; Set bit 7 to enable transparency
+	ld (de), a
+	ret
 
 ; Sets the FLASH flag passed in A register in the ATTR_T variable
 FLASH_TMP:
 	ld de, ATTR_T
 	jr __SET_FLASH
+    ENDP