CLYT (.bclyt) is the layout format used on the 3DS. It stands for (Binary) CTR Layout, and is similar to the RLYT format used on the Wii.
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (CLYT) | 
| 0x04 | 0x2 | UInt16 | Byte Order Mark | 
| 0x06 | 0x2 | UInt16 | Header Length | 
| 0x08 | 0x4 | UInt32 | Revision | 
| 0x0C | 0x4 | UInt32 | File Size | 
| 0x10 | 0x4 | UInt32 | Nr Sections | 
lyt1 (Layout 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (lyt1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x4 | UInt32 | Origin type 
| Value | Meaning |  
| 0 | Classic |  
| 1 | Normal |  | 
| 0x0C | 0x8 | Vector2 | Canvas Size | 
txl1 (Texture List 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (txl1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x4 | UInt32 | Nr Textures = N | 
| 0x0C | N * 4 | UInt32[] | Texture Name Offsets (relative to the start of this array) | 
After this, the null terminated names follow.
fnl1 (Font List 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (fnl1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x4 | UInt32 | Nr Fonts = N | 
| 0x0C | N * 4 | UInt32[] | Font Name Offsets (relative to the start of this array) | 
After this, the null terminated names follow.
mat1 (Materials 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (mat1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x4 | UInt32 | Nr Materials = N | 
| 0x0C | N * 4 | UInt32[] | Material Entry Offsets (relative to the start of this section) | 
After this, the material entries follow.
| Offset | Size | Type | Description | 
| 0x00 | 0x14 | String | Material Name | 
| 0x14 | 0x4 | RGBA8 | Tev Color (Buffer Color?) | 
| 0x18 | 0x18 | RGBA8[6] | Tev Constant Colors | 
| 0x30 | 0x4 | UInt32 | Flags / bitfield 
| Bit | Flag / data |  
| 0-1 | Nr texMap |  
| 2-3 | Nr texMatrix |  
| 4-5 | Nr texCoordGen |  
| 6-8 | Nr tevStage |  
| 9 | Has alphaCompare |  
| 10 | Has blendMode |  
| 11 | Use Texture Only |  
| 12 | Separate Blend Mode |  
| 14 | Has Indirect Parameter |  
| 15-16 | Nr projectionTexGenParameter |  
| 17 | Has Font Shadow Parameter |  | 
Texture Map Entry
| Offset | Size | Type | Description | 
| 0x00 | 0x2 | UInt16 | Texture Index | 
| 0x02 | 0x1 | Byte | Bitfield 
| Bit | Data |  
| 0-1 | Wrap S (Clamp = 0, Repeat = 1, Mirror = 2) |  
| 2-3 | Min Filter (0 = Near, 1 = Linear) |  | 
| 0x02 | 0x1 | Byte | Bitfield 
| Bit | Data |  
| 0-1 | Wrap T (Clamp = 0, Repeat = 1, Mirror = 2) |  
| 2-3 | Mag Filter (0 = Near, 1 = Linear) |  | 
Texture Matrix Entry
| Offset | Size | Type | Description | 
| 0x00 | 0x8 | Vector2 | Translation | 
| 0x08 | 0x4 | Single | Rotation | 
| 0x0C | 0x8 | Vector2 | Scale | 
TODO: texCoordGen, tevStage, alphaCompare, blendMode, etc...
pan1 (Pane 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (pan1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x1 | UInt8 | Flags 
| Bit | Flag |  
| 0 | Visible |  
| 1 | InfluencedAlpha |  
| 2 | LocationAdjust |  | 
| 0x09 | 0x1 | UInt8 | Origin | 
| 0x0A | 0x1 | UInt8 | Alpha | 
| 0x0B | 0x1 | UInt8 | Pane magnification flags 
| Bit | Flag |  
| 0 | IgnorePartsMagnify |  
| 1 | AdjustToPartsBounds |  | 
| 0x0C | 0x18 | String | Pane name | 
| 0x24 | 0xC | Vector3 | Translation | 
| 0x30 | 0xC | Vector3 | Rotation | 
| 0x3C | 0x8 | Vector2 | Scale | 
| 0x48 | 0x8 | Vector2 | Size | 
pic1 (Picture 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (pic1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x4 | RGBA8 | Top left vertex color | 
| 0x0C | 0x4 | RGBA8 | Top right vertex color | 
| 0x10 | 0x4 | RGBA8 | Bottom left vertex color | 
| 0x14 | 0x4 | RGBA8 | Bottom right vertex color | 
| 0x18 | 0x2 | UInt16 | Material ID | 
| 0x1A | 0x2 | UInt16 | Nr texture coordinates = N | 
| Texture coordinates entry | 
| 0x1C + N*0x20 | 0x8 | Vector2 | Top left vertex texture coordinate | 
| 0x24 + N*0x20 | 0x8 | Vector2 | Top right vertex texture coordinate | 
| 0x2C + N*0x20 | 0x8 | Vector2 | Bottom left vertex texture coordinate | 
| 0x34 + N*0x20 | 0x8 | Vector2 | Bottom right vertex texture coordinate | 
txt1 (Text 1)
wnd1 (Window 1)
bnd1 (Bounding 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (bnd1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x2 | UInt16? | ? | 
| 0x0A | 0x2 | UInt16? | ? | 
| 0x0C | ? (0x10 up to 0x30) | String | Bounding name | 
| 0x3C | 0x8 | Vector2 | ? | 
| 0x44 | 0x4 | Vector2 | ? | 
| ⋮ | ⋮ | ⋮ | ⋮ | 
pts1 (Parts 1)
pas1 (Pane Start 1)
Starts a pane.
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (pas1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
pae1 (Pane End 1)
Ends a pane.
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (pae1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
grp1 (Group 1)
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (grp1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
| 0x08 | 0x10 | String | Group Name | 
| 0x18 | 0x4 | UInt32 | Nr Pane References (=N) | 
| 0x1C | 0x10 * N | String[N] | Pane References | 
grs1 (Group Start 1)
Starts a group.
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (grs1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
gre1 (Group End 1)
Ends a group.
| Offset | Size | Type | Description | 
| 0x00 | 0x4 | String | Signature (gre1) | 
| 0x04 | 0x4 | UInt32 | Section Size | 
See also
http://florian.nouwt.com/wiki/index.php/CLYT_%28File_Format%29
https://github.com/Gericom/EveryFileExplorer/tree/master/3DS/NintendoWare/LYT1