Mode 0

What is Mode 0?

Mode 0 is the first mode on the SNES, characterized by its offer of four layers, as opposed to the normal three Mode 1 offers you. However, there are two significant drawbacks: you only have four colors (3 actual colors plus transparency) per palette, and the layer 3 tilemap is halved to make room for layer 4. However, the latter drawback can be circumvented by sacrificing GFX slots.

Thankfully, the first drawback does not apply on the sprite layer, so no worries about your sprites!

Applications of Mode 0

When it comes to the SNES library of games, only a few have used Layer 4, such as Super Mario Kart, Super Mario World 2 - Yoshi's Island, S.O.S., and Earthbound.

To make things more interesting, in the field of Super Mario World hacking, a few hacks and contest levels have used it, such as ASMWCP, LMPuny's work-in-progress SUPER MARIO BROS. Returns, idol and Katrina's Chocolate Level Design Contest 2018 entry lightest, and AnasMario130's Power Mario Contest entry Pyro-Blue's Fort.

Palette and Tilemap Distribution

As mentioned in the previous heading, Mode 0 can only offer you four colors per palette, including transparency. Each layer takes up 8 four-color palettes distributed in two rows each. Layer 1 takes up rows 0-1, layer 2 rows 2-3, layer 3 rows 4-5, and layer 4 rows 6-7.

As for the tilemap, it is 2bpp, but the size must be 4 KB. However, the arrangement for the tilemap is doubled, meaning that in a graphics editor like YY-Chr, you can have eight rows' worth of graphics instead of the usual four.

How to Use Mode 0 in Super Mario World

1. First of all, please use one of the given codes in a level using UberASM Tool before proceeding:

Stationary Layer 4, by LMPuny

init:
LDA #$51 : STA $2109
LDA #$59 : STA $210A
LDA #$44 : STA $210C
STZ $3E

LDA #$11 : STA $212C : STA $212E
LDA #$0E : STA $212D : STA $212F
    
REP #$20 : LDA $20 : CLC : ADC #$0080 : SEP #$20
STA $2112 : XBA : STA $2112
    
REP #$20 : LDA $24
CLC : ADC #$0070 : SEP #$20
STA $2114 : XBA : STA $2114

RTL

Automatically-Scrolling Layer 4, by LMPuny

!base1 = $0000
!base2 = $0000

if read1($00FFD5) == $23
sa1rom
!base1 = $3000
!base2 = $6000
endif

!FreeRAM = $60

init:
stz !FreeRAM
stz !FreeRAM+1

LDA #$51 : STA $2109
LDA #$59 : STA $210A
LDA #$44 : STA $210C
STZ $3E

LDA #$11 : STA $212C : STA $212E
LDA #$0E : STA $212D : STA $212F
    
REP #$20 : LDA $20 : CLC : ADC #$0080 : SEP #$20
STA $2112 : XBA : STA $2112
    
REP #$20 : LDA $24
CLC : ADC #$0070 : SEP #$20
STA $2114 : XBA : STA $2114
RTL

Camera-Based Scrolling Layer 4, by LMPuny; scrolling code by MolSno from his Layer 4 code; however the init: code is broken in that layer 4 doesn't show up at all

init:

LDA #$51 : STA $2109
LDA #$59 : STA $210A
LDA #$44 : STA $210C
STZ $3E

LDA #$11 : STA $212C : STA $212E
LDA #$0E : STA $212D : STA $212F
    
REP #$20 : LDA $20 : CLC : ADC #$0080 : SEP #$20
STA $2112 : XBA : STA $2112
    
REP #$20 : LDA $24
CLC : ADC #$0070 : SEP #$20
STA $2114 : XBA : STA $2114


main:
; Layer 4 H-Scroll = Layer 3 H-Scroll / 4
REP #$20 : LDA $22 : LSR A : LSR A : SEP #$20
STA $2113 : XBA : STA $2113
	
; Layer 4 V-Scroll = Layer 3 V-Scroll
REP #$20 : LDA $24 : SEP #$20
STA $2114 : XBA : STA $2114
RTL

Bugs so far:

1. Layer 2/3 translucency doesn't work when set in LM.
2. The 2nd layer 4 code doesn't seem to initialize the layer 4 BG's position at all, so you will notice that the position of layer 4 in a section of your level will be carried off from the previous section's. A workaround to this would be swapping their priorities around in LM's Layer 3 Tilemap Editor using the Priority -- tab. More on that later.

Please make a fix to these two bugs, if possible, and cross them out respectively.

2. Press Ctrl+F7 on a level to change Lunar Magic's graphics viewer mode to 2bpp.

3. Use the following 2bpp-trimmed SMW tileset for your Layer 4 levels by AnasMario130 (includes most of SMW's important animations and graphics, such as the cave tileset, coins, question blocks, etc.):

First Tileset: Cave

https://cdn.discordapp.com/attachments/334352091340472340/648173302530965504/template.zip

A GIF of the cave tileset as well as the animations

A picture of the map16 data included in template.zip. Discolored tiles are from the ghost ship tileset

Second Tileset: Ghost Ship

Link: https://cdn.discordapp.com/attachments/334352091340472340/648226959477964816/ghostship.zip

A GIF of the tileset in action with all layers being shown individually later on in the GIF; recorded with LiceCAP on ZMZ

The map16 of the ghost ship tileset, now with the correct palette!

ExAnimation in Mode 0 levels

ExAnimation in Mode 0 levels is not really difficult once you adapt to it, but it may seem tricky at first glance. The main reason for this is that even in LM's 2bpp graphics viewing mode, ExAnimation tiles are still rendered in 4bpp, thus becoming garbled. Also the size of the frames to be animated is condensed into 8x8 tiles according to the following arrangement:

The recommended arrangement for your ExAnimation frames for better understanding of Mode 0 ExAnimation. Here, the AN2 file is ExGFX405

The actual rendering of the tiles, starting from 0x780 and ending at 0X7FF, in the 8x8 Tile Editor window. As explained earlier, the gaps from the above screenshot of ExGFX405, are cut out

ExAnimation Tile Explanation

780-781, 790-791, 7A0-7A1, 7B0-7B1: ?-block

782-783, 792-793, 7A2-7A3, 7B2-7B3: Coin

784-785: Used brown block

794-795, 7A4-7A5, 7B4-7B5, 7C4-7C5: Turning turnblock

786-787, 796-797: Boo animation 1

7A6-7A7, 7B6-7B7: Boo animation 2

7C0-7C1, 7D0-7D1, 7E0-7E1, 7F0-7F1: Note block

7CA-7CB, 7DA-7DB, 7EA-7EB, 7FA-7FB: Seaweed animation 1

7CC-7CD, 7DC-7DD: Muncher

7CE-7CF, 7DE-7DF, 7EE-7EF, 7FE-7FF: Seaweed animation 2

First Example for ExAnimation

We wanna animate the ?-block. How will we do it?

1. First of all, before animating anything, there is one important point to keep in mind: the destination tile for your ExAnimation tile in the ExAnimation window must be divided by 2 in hex, otherwise the destination will not be as expected. So for example, if your destination tile is EA, it should be divided by 2 in hex in a calculator, like your computer's built-in one or something else, to get 75. Put 75 instead in the destination tile text box.

For our example, the ?-block's final destination is at (60/2=)30. If we were to put 60 instead, the final destination would be at (60*2=)C0, which is not what we want.

2. For the ?-block you might expect the animation type to be 4 8x8s: line, but that is completely wrong! Since the frames are condensed in 8x8 tiles under the 8x8 Tile Editor window, it should be 2 8x8s: line instead. Refer to the ExAnimation tile explanation section for the ?-block and the 8x8 Tile Editor. The correct tiles to be input in the ExAnimation window are 780, 790, 7A0, and 7B0 and the type should be 2 8x8s: line.

Result!

Now, you just got your first 2bpp 0 animation set up! The same procedure goes for layer 3 ExAninimated tiles, except that you can directly put in your destination file (from 0x1C00-0x1DFF)!