Improved graphics

- Added multicolor graphic mode with custom charset, for text and tiles
- Added some debug options in Makefile

NOTE: code is functioning and correct, but really needs a big cleanup a
logical reorganization!

.gitignore

@@ -1 +1,3 @@
-snake.prg
+*.prg
+*.out
+symbols.txt

Makefile

@@ -1,5 +1,8 @@
 64:
-	dasm snake.asm -DSYSTEM=64 -osnake.prg
+	dasm snake.asm -DSYSTEM=64 -DDEBUG=0 -osnake.prg
+
+debug:
+	dasm snake.asm -DSYSTEM=64 -DDEBUG=1 -ssymbols.txt -osnake.prg
 
 16:
 	dasm snake.asm -DSYSTEM=16 -osnake.prg

multicolor.asm

@@ -0,0 +1,148 @@
+		processor 6502
+
+multicolor SUBROUTINE
+
+; Prepare data struct for MultiColor mode
+; ----------------------------------------------------------------------
+multicolorInit:
+	; Deactivate interrupt
+	; This is needed to avoid calls from I/O while dealing with bank
+	; switching (I/O addresses are the same)
+	sei
+
+	; Put char ROM in CPU address space
+	; It becomes visible at $d000
+	; This overrides I/O
+;	lda $1
+;	and #$fb
+;	sta $1
+
+	; Copy ROM original content from $d000 to $3800
+;	ldx #0
+;.copyLoop:
+;	lda $d000,x
+;	sta $3800,x
+;	lda $d100,x
+;	sta $3900,x
+;	lda $d200,x
+;	sta $3a00,x
+;	lda $d300,x
+;	sta $3b00,x
+;	lda $d400,x
+;	sta $3c00,x
+;	lda $d500,x
+;	sta $3d00,x
+;	lda $d600,x
+;	sta $3e00,x
+;	lda $d700,x
+;	sta $3f00,x
+;	inx
+;	bne .copyLoop
+
+	; Copy The GGS Font and
+	; make higher half the inverse of lower one
+	ldx #$00
+.tggsCopy
+	dex
+	lda .tggsFont,x
+	sta $3800,x
+	eor #$ff
+	sta $3c00,x
+	lda .tggsFont + $100,x
+	sta $3900,x
+	eor #$ff
+	sta $3d00,x
+	lda .tggsFont + $200,x
+	sta $3a00,x
+	eor #$ff
+	sta $3e00,x
+	lda .tggsFont + $300,x
+	sta $3b00,x
+	eor #$ff
+	sta $3f00,x
+	cpx #$0
+	bne .tggsCopy
+
+	; Edit character definitions in RAM (using previous defined table)
+	ldx #$8
+.editLoop:
+	dex
+	lda .multicolorSnakeTile,x
+	sta $3800 + SNAKE_TILE * 8,x
+	lda .multicolorFoodTile,x
+	sta $3800 + FOOD_TILE * 8,x
+;	lda .multicolorOtherTile,x
+;	sta $3800 + SOME_TILE * 8,x
+;	...
+	cpx #$0
+	bne .editLoop
+
+	; Put ROM away from CPU address space, and re-enable I/O
+;	lda $1
+;	ora #$4
+;	sta $1
+
+; Set foreground color in [8-F] to all locations to enable multicolor mode for every single char
+;	ldx #0
+;	lda #$d
+;colorLoop:
+;	sta $d800,x
+;	sta $d900,x
+;	sta $da00,x
+;	sta $db00,x
+;	inx
+;	bne colorLoop
+
+	; Tell VIC-II to read characters from $3800 = 0xe * 0x400
+	lda $d018
+	ora #$0e
+	sta $d018
+
+	; Re-enable interrupts and return
+	cli
+	rts
+
+; Activate multicolor mode
+; ----------------------------------------------------------------------
+multicolorOn:
+	; Set colors
+	lda #9
+	sta $d021	; 00 is brown
+	lda #2
+	sta $d022	; 01 is red
+	lda #13
+	sta $d023	; 10 is green
+				; and of course
+				; 11 is the colour specified in color RAM
+
+	lda $d016
+	ora #$10
+	sta $d016
+
+	rts
+
+; Deactivate multicolor mode
+; ----------------------------------------------------------------------
+multicolorOff:
+	lda $d016
+	and #$ef
+	sta $d016
+	rts
+
+; Costants
+; ----------------------------------------------------------------------
+.multicolorCommodoreTile:
+	BYTE #$00,#$30,#$cc,#$ca,#$c0,#$c5,#$cc,#$30
+.multicolorSnakeTile:
+	BYTE #$00,#$28,#$ab,#$ab,#$ab,#$ab,#$28,#$00
+.multicolorFoodTile:
+	BYTE #%00010101
+	BYTE #%10010101
+	BYTE #%10010101
+	BYTE #%10010101
+	BYTE #%10101000
+	BYTE #%00100000
+	BYTE #%00100000
+	BYTE #%10000000
+.tggsFont
+	INCBIN "tggs.font"

snake.asm

@@ -103,10 +103,10 @@ SCREEN_W    =   40
 SCREEN_H    =   24
 ; Snake features
 SNAKE_TILE  =   81
-SNAKE_COLOR =   5
+SNAKE_COLOR =   13
 ; Food features
 FOOD_TILE   =   90
-FOOD_COLOR  =   15
+FOOD_COLOR  =	11 
 
 ; Strings
 gameoverString:
@@ -128,10 +128,19 @@ intro2string:
 intro3string:
     BYTE "(C) 2018"
     BYTE #0
-colorshade: ; a shade from dark-gray to bright yellow, and vice-versa (40 columns)
+colorshade: ; a gradient of dark-bright-dark, with only hi-res colors (40 columns)
-    BYTE    #11,#11,#11,#11,#11,#12,#12,#12,#12,#12,#5,#5,#5
+	BYTE	#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5,#5	
-    BYTE    #13,#13,#13,#13,#7,#7,#7,#7,#7,#7
+;	BYTE	#6,#6,#6
-    BYTE    #13,#13,#13,#13,#5,#5,#5,#12,#12,#12,#12,#12,#11,#11,#11,#11,#11
+;	BYTE	#2,#2,#2,#2
+;	BYTE	#5,#5,#5,#5
+;	BYTE	#7,#7,#7,#7
+;	BYTE	#3,#3,#3,#3
+;	BYTE	#1,#1,#1,#1
+;	BYTE	#3,#3,#3,#3
+;	BYTE	#7,#7,#7,#7
+;	BYTE	#5,#5,#5,#5
+;	BYTE	#2,#2,#2,#2
+;	BYTE	#6,#6,#6
 scoreString:
 	BYTE "POINTS"
 	BYTE #0
@@ -184,6 +193,9 @@ start:
     lda #0
     jsr sidtune
 
+	; Initialize MultiColor mode
+	jsr multicolorInit
+
     ; Set status as first-time intro playing
     lda #ST_INTRO0
     sta status
@@ -224,6 +236,9 @@ endless:
 ; Full game reset
 ; ----------------------------------------------------------------------
 fullreset:
+	; Turn MultiColor mode on
+	jsr multicolorOn
+
     ; Clear screen
     ldx #$ff
     lda #$20
@@ -236,11 +251,9 @@ fullresetCLS:
     cpx #$ff
     bne fullresetCLS
 
-    ; Set screen colors
+    ; Set overscan
-    lda #12
+    lda #11
-    sta $d020   ; overscan
+    sta $d020
-    lda #9
-    sta $d021   ; center
     ; Upper bar -- fill with reversed spaces, color yellow
     ldx #39
 upperbarLoop:
@@ -280,6 +293,8 @@ upperbarLoop:
 ; Intro reset
 ; ----------------------------------------------------------------------
 introreset:
+	jsr multicolorOff
+
     ; Clear screen
     ldx #$ff
     lda #$20
@@ -292,9 +307,7 @@ introresetCLS:
     cpx #$ff
     bne introresetCLS
 
-    ; Copy shade colors from costant table to color RAM for 2nd and 4th
+    ; Copy shade colors from costant table to color RAM for 2nd and 4th line of text
-    ; line of text. Soon there will be some text bouncing on these
-    ; lines
     ldx #39
 introresetColorShade
     lda colorshade,x
@@ -307,7 +320,6 @@ introresetColorShade
     ; Set screen colors
     lda #0
     sta $d020   ; overscan
-    lda #0
     sta $d021   ; center
 
     ; Print website
@@ -349,6 +361,12 @@ irq:
     tya
     pha
 
+#if DEBUG = 1
+	; Change background to visually see the ISR timing
+	lda #2
+	sta $d020
+#endif
+
     ; Check status and call appropriate sub-routine
     ; Sort of switch-case
     lda status
@@ -377,9 +395,13 @@ checkEndStatus:
     jsr sidtune + 3
 
     ; Increase random value
-    ldx random
+    inc random
-    inx
+
-    stx random
+#if DEBUG = 1
+	; Change background back again to visally see ISR timing
+	lda #11
+	sta $d020
+#endif
 
     ; Restore registers from stack
     pla
@@ -949,6 +971,10 @@ printIntroEndCheck:
 printIntroEnd:
     rts
 
+; Include
+; ______________________________________________________________________
+	INCLUDE "multicolor.asm"
+
 ;
 ; coded during december 2017
 ; by giomba -- giomba at glgprograms.it