Palette cycling

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Palette cycling animates by color alone. The NES has 4 background and 4 sprite palettes of 3 colors each, plus a shared backdrop¹, so a program that rewrites one entry recolors every tile drawn with that palette, with no tile data changed.

#Parameters

Super Mario Bros. puts the cycled color in entry 1 of the palette at $3F0C and keeps the other entries from the area’s row². Mega Man 2 stores each stage’s set count and frame byte ahead of its palettes, and steps when a per-frame counter passes the frame byte³.

Games

Game	Year	How	Note
Super Mario Bros.	1985	Color step	? blocks and coins shimmer through six colors, a step every eighth frame
Mega Man 2	1988	Palette sets	a stage can animate by stepping through a list of palettes

Every claim about this mechanic, by game (3)

Super Mario Bros. 1985	Every 8th frame `ColorRotation` rewrites background palette 3 at `$3F0C`, putting the next of six colors, `$27`, `$27`, `$27`, `$17`, `$07`, `$17`, in its second entry, so the question blocks and coins shimmer on a 48-frame loop.	Code
Mega Man 2 1988	Once a frame `_background_palette` counts up to a stage's frame byte and then copies the next 16-byte background palette set into the working palette, wrapping after the stage's set count; Heat Man's stage has 3 sets and a frame byte of 6, so its palette 3 rotates `$36`, `$26`, `$16` one step every 7 frames.	Code
general	Backgrounds and sprites each have 4 palettes of 4 entries at `$3F00`-`$3F1F`; entry 0 of each is transparent, and entry 0 of palette 0 is the backdrop shared by both, so each palette shows 3 colors of its own.	Wiki

References

^Backgrounds and sprites each have 4 palettes of 4 entries at $3F00-$3F1F; entry 0 of each is transparent, and entry 0 of palette 0 is the backdrop shared by both, so each palette shows 3 colors of its own.WikiNESdev Wiki, “PPU palettes”
How we know
Backgrounds and sprites each have 4 palettes of 4 colors, located at $3F00-$3F1F in VRAM. … Entry 0 of each palette is unique in that it is transparent, so its color value is normally unused. … The backdrop color is the single color shown behind both the background and sprites, wherever both layers are transparent.
Palette RAM · archived copy ↗
Checked against the evidence by its author, an AI model, 2026-10-21.
Checked by a second AI model, 2026-10-21.
In the claim ledger

^ a bEvery 8th frame ColorRotation rewrites background palette 3 at $3F0C, putting the next of six colors, $27, $27, $27, $17, $07, $17, in its second entry, so the question blocks and coins shimmer on a 48-frame loop.CodeXkeeper0/smb1

How we know

1386ColorRotatePalette:
1387	.db $27, $27, $27, $17, $07, $17
⋮
1390	.db $3f, $0c, $04, $ff, $ff, $ff, $ff, $00

src/prg.asm lines 1386–1390 at 1cc3c92 · upstream ↗

1399ColorRotation:
1400	LDA FrameCounter                             ; get frame counter
1401	AND #$07                                     ; mask out all but three LSB
1402	BNE ExitColorRot                             ; branch if not set to zero to do this every eighth frame

src/prg.asm lines 1399–1402 at 1cc3c92 · upstream ↗

1429	LDY ColorRotateOffset                        ; get color cycling offset
1430	LDA ColorRotatePalette,y
1431	STA VRAM_Buffer1+4,x                         ; get and store current color in second slot of palette
⋮
1438	CMP #$06                                     ; check to see if it's still in range

src/prg.asm lines 1429–1441 at 1cc3c92 · upstream ↗

Checked against the evidence by its author, an AI model, 2026-10-21.

Checked by a second AI model, 2026-10-21.

In the claim ledger

^ a bOnce a frame _background_palette counts up to a stage's frame byte and then copies the next 16-byte background palette set into the working palette, wrapping after the stage's set count; Heat Man's stage has 3 sets and a frame byte of 6, so its palette 3 rotates $36, $26, $16 one step every 7 frames.Codelsmmega/mm2

How we know

1_background_palette:
⋮
4	LDA apalette_animation_frame
5	BEQ @skip
6	INC z:zpalette_animation_timer
7	CMP z:zpalette_animation_timer
8	BCS @skip
9	LDA #$00
10	STA z:zpalette_animation_timer
11	INC z:zcurrent_palette_no
12	LDA z:zcurrent_palette_no
13	CMP ano_of_palette
⋮
15	LDA #$00
⋮

home/background_palette.asm lines 1–32 at 94f0bf3 · upstream ↗

1_nmi_wait_0e:
⋮
6	JSR _background_palette
7	LDA #$00
8	STA z:znmi_wait
⋮
10@loop:
11	LDA z:znmi_wait
12	BEQ @loop

home/nmi_wait.asm lines 1–12 at 94f0bf3 · upstream ↗

1;heatman palette init
2	;     number of background animation palette(s), frame(s)
3	.BYTE 3, 6
⋮
9	.BYTE black, pale_red,  white_red,  light_red
⋮
22	.BYTE black, pale_red,  white_red,  light_red
⋮
28	.BYTE black, white_red, light_red,  pale_red
⋮
34	.BYTE black, light_red, pale_red,   white_red

stages/heatman_wily1/heatman_wily1_palette_init.asm lines 1–34 at 94f0bf3 · upstream ↗

2	dark_gray
⋮
16	light_gray
⋮
22	light_red
⋮
29	white_gray = $20
⋮
42	pale_gray = $30
⋮
48	pale_red

constants/palettes.asm lines 1–55 at 94f0bf3 · upstream ↗

Checked against the evidence by its author, an AI model, 2026-10-21.

Checked by a second AI model, 2026-10-21.

In the claim ledger

Sources

Code

doppelganger and Xkeeper. 2022. “smb1: Super Mario Bros. disassembly for asm6f (Xkeeper0/smb1).” Commit 1cc3c92. Xkeeper0/smb1 @ 1cc3c92 · licence, all uses
lsmmega. 2026. “mm2: Mega Man 2 disassembly (lsmmega/mm2).” Commit 94f0bf3. lsmmega/mm2 @ 94f0bf3 · licence, all uses

Secondary

NESdev Wiki contributors. n.d. “PPU palettes.” NESdev Wiki. Version oldid 24257. original · archived · licence, all uses

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