Sprite flicker

References

1. ^The PPU's object attribute memory (OAM) holds a display list of up to 64 sprites, 4 bytes each, and sprite 0 is the one at OAM bytes $00-$03.WikiNESdev Wiki, “PPU OAM”
   How we know

   contains a display list of up to 64 sprites, where each sprite's information occupies 4 bytes.

   Sprite 0 is the sprite controlled by OAM addresses $00-$03

   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

2. ^ abOn each scanline the PPU copies the sprites in range, searching OAM in order, into a secondary OAM that holds 8, so a scanline shows at most 8 sprites and the later ones in OAM order drop out.WikiNESdev Wiki, “PPU OAM”
   How we know

   the PPU contains 32 bytes (enough for 8 sprites) of secondary OAM memory … a linear search of the entire primary OAM is carried out to find sprites that are within y range for the next scanline

   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

3. ^ abOn even frames _sprites writes Mega Man's object slots (0 to $0F), then the enemies' ($10 to $1F), then the energy meters; on odd frames it writes the meters first and the slots in reverse, $1F down to $10, then $0F down to 0, so objects that lose the 8-per-scanline race lose it only every other frame.Codelsmmega/mm2revised
   How we know

   12@time_stopper_flag_not_set:
   13	LDA z:znmi_frame
   14	AND #%00000001
   15	BNE @invert
   ⋮
   21@loop_1:
   22	JSR _draw_megaman_with_animation
   ⋮
   26	CMP #$10
   27	BNE @loop_1
   ⋮
   29@loop_2:
   30	JSR _draw_enemies_with_animation
   ⋮
   34	CMP #$20
   35	BNE @loop_2
   ⋮
   

   43@invert:
   44	JSR _draw_bar
   ⋮
   47	LDA #$1F
   48	STA z:zsprites_pointer
   ⋮
   50@loop_3:
   51	JSR _draw_enemies_with_animation
   52	BCS @max_2
   53	DEC z:zsprites_pointer
   ⋮
   58@loop_4:
   59	JSR _draw_megaman_with_animation
   60	BCS @max_2
   61	DEC z:zsprites_pointer
   ⋮
   

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

   Revised after a check by a second AI model, 2026-10-21.

   In the claim ledger

4. ^ abEvery unpaused frame SpriteShuffler adds one of three amounts, $58, $48, or $38 in turn, to each object's OAM offset at or above $28, wrapping within $28-$FF, so the objects' sprites change OAM slots each frame and a ninth sprite on a line drops out on different frames.CodeXkeeper0/smb1
   How we know

   165	LDA GamePauseStatus                          ; if in pause mode, do not bother with sprites at all
   ⋮
   168	JSR MoveSpritesOffscreen
   169	JSR SpriteShuffler
   

   240SpriteShuffler:
   ⋮
   242	LDA #$28                                     ; load preset value which will put it at
   243	STA $00                                      ; sprite #10
   244	LDX #$0e                                     ; start at the end of OAM data offsets
   245ShuffleLoop:
   246	LDA SprDataOffset,x                          ; check for offset value against
   247	CMP $00                                      ; the preset value
   248	BCC NextSprOffset                            ; if less, skip this part
   249	LDY SprShuffleAmtOffset                      ; get current offset to preset value we want to add
   250	CLC
   251	ADC SprShuffleAmt,y                          ; get shuffle amount, add to current sprite offset
   252	BCC StrSprOffset                             ; if not exceeded $ff, skip second add
   ⋮
   

   2225	LDA #$38                                     ; load sprite shuffle amounts to be used later
   2226	STA SprShuffleAmt+2
   2227	LDA #$48
   2228	STA SprShuffleAmt+1
   2229	LDA #$58
   2230	STA SprShuffleAmt
   

   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