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iigs-game-engine/src/blitter/Tiles.s

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; Collection of functions that deal with tiles. Primarily rendering tile data into
; the code fields.
;
; Tile data can be done faily often, so these routines are performance-sensitive.
;
; CopyTileConst -- the first 16 tile numbers are reserved and can be used
; to draw a solid tile block
; CopyTileLinear -- copies the tile data from the tile bank in linear order, e.g.
; 32 consecutive bytes are copied
; _RenderTile
;
; A high-level function that takes a 16-bit tile descriptor and dispatched to the
; appropriate tile copy routine based on the descriptor flags
;
; Bit 15 14 13 12 11 10 09 08 07 06 05 04 03 02 01 00
; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
; |xx|xx|FF|MM|DD|VV|HH| | | | | | | | | |
; +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
; \____/ | | | | | \________________________/
; | | | | | | Tile ID (0 to 511)
; | | | | | |
; | | | | | +-- H : Flip tile horizontally
; | | | | +----- V : Flip tile vertically
; | | | +-------- D : Render as a Dynamic Tile (Tile ID < 32, V and H have no effect)
; | | +----------- M : Apply tile mask
; | +-------------- F : Overlay a fringe tile
; +------------------- Reserved (must be zero)
;
; Each logical tile (corresponding to each Tile ID) actually takes up 128 bytes of memory in the
; tile bank
;
; +0 : 32 bytes of tile data
; +32 : 32 bytes of tile mask
; +64 : 32 bytes of horizontally flipped tile data
; +96 : 32 bytes of horizontally flipped tile mask
;
; It is simply too slow to try to horizontally reverse the pixel data on the fly. This still allows
; for up to 512 tiles to be stored in a single bank, which should be sufficient.
TILE_CTRL_MASK equ $FE00
TILE_PROC_MASK equ $F800 ; Select tile proc for rendering
; Temporary direct page locatinos used by some of the complex tile renderers
_X_REG equ tiletmp
_Y_REG equ tiletmp+2
_T_PTR equ tiletmp+4 ; Copy of the tile address pointer
_BASE_ADDR equ tiletmp+6 ; Copy of BTableLow for this tile
_SPR_X_REG equ tiletmp+8 ; Cache address of sprite plane source for a tile
; Low-level function to take a tile descriptor and return the address in the tiledata
; bank. This is not too useful in the fast-path because the fast-path does more
; incremental calculations, but it is handy for other utility functions
;
; A = tile descriptor
;
; The address is the TileID * 128 + (HFLIP * 64)
GetTileAddr ENT
jsr _GetTileAddr
rtl
_GetTileAddr
asl ; Multiply by 2
bit #2*TILE_HFLIP_BIT ; Check if the horizontal flip bit is set
beq :no_flip
inc ; Set the LSB
:no_flip and #TILE_ID_MASK*2 ; Mask out non-id bits
asl ; x4
asl ; x8
asl ; x16
asl ; x32
asl ; x64
asl ; x128
rts
; On entry
;
; B is set to the correct BG1 data bank
; A is set to the the tile descriptor
; Y is set to the top-left address of the tile in the BG1 data bank
;
; tmp0/tmp1 is reserved
_RenderTileBG1
pha ; Save the tile descriptor
and #TILE_VFLIP_BIT+TILE_HFLIP_BIT ; Only horizontal and vertical flips are supported for BG1
xba
tax
ldal :actions,x
stal :tiledisp+1
pla
and #TILE_ID_MASK ; Mask out the ID and save just that
_Mul128 ; multiplied by 128
tax
:tiledisp jmp $0000
:actions dw _TBSolidBG1_00,_TBSolidBG1_0H,_TBSolidBG1_V0,_TBSolidBG1_VH
; Given an address to a Tile Store record, dispatch to the appropriate tile renderer. The Tile
; Store record contains all of the low-level information that's needed to call the renderer.
;
; Y = address of tile
RenderTile ENT
phb
phk
plb
jsr _RenderTile2
plb
rtl
_RenderTile2
lda TileStore+TS_TILE_ID,y ; build the finalized tile descriptor
ldx TileStore+TS_SPRITE_FLAG,y ; This is a bitfield of all the sprites that intersect this tile, only care if non-zero or not
beq :nosprite
ora #TILE_SPRITE_BIT
ldx TileStore+TS_SPRITE_ADDR,y
stx _SPR_X_REG
:nosprite
and #TILE_CTRL_MASK
xba
tax
lda TileProcs,x ; load and patch in the appropriate subroutine
sta :tiledisp+1
ldx TileStore+TS_TILE_ADDR,y ; load the address of this tile's data (pre-calculated)
sep #$20 ; load the bank of the target code field line
lda TileStore+TS_CODE_ADDR_HIGH,y
pha
rep #$20
lda TileStore+TS_CODE_ADDR_LOW,y ; load the address of the code field
pha
lda TileStore+TS_BASE_ADDR,y ; load the base address of the code field
sta _BASE_ADDR
lda TileStore+TS_WORD_OFFSET,y
ply
plb ; set the bank
; B is set to the correct code field bank
; A is set to the tile word offset (0 through 80 in steps of 4)
; Y is set to the top-left address of the tile in the code field
; X is set to the address of the tile data
:tiledisp jmp $0000 ; render the tile
; Reference all of the tile rendering subroutines defined in the TileXXXXX files. Each file defines
; 8 entry points:
;
; One set for normal, horizontally flipped, vertically flipped and hors & vert flipped.
; A second set that are optimized for when EngineMode has BG1 disabled.
TileProcs dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 00000 : normal tiles
dw _TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00 ; 00001 : dynamic tiles
dw _TBMaskedTile_00,_TBMaskedTile_0H,_TBMaskedTile_V0,_TBMaskedTile_VH ; 00010 : masked normal tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00 ; 00011 : masked dynamic tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00
; Fringe tiles not supported yet, so just repeat the block from above
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 00100 : fringed normal tiles
dw _TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00 ; 00101 : fringed dynamic tiles
dw _TBMaskedTile_00,_TBMaskedTile_0H,_TBMaskedTile_V0,_TBMaskedTile_VH ; 00110 : fringed masked normal tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00 ; 00111 : fringed masked dynamic tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00
; High-priority tiles without a sprite in front of them are just normal tiles. Repeat the top half
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 01000 : high-priority normal tiles
dw _TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00 ; 01001 : high-priority dynamic tiles
dw _TBMaskedTile_00,_TBMaskedTile_0H,_TBMaskedTile_V0,_TBMaskedTile_VH ; 01010 : high-priority masked normal tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00 ; 01011 : high-priority masked dynamic tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 01100 : high-priority fringed normal tiles
dw _TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00,_TBDynamicTile_00 ; 01101 : high-priority fringed dynamic tiles
dw _TBMaskedTile_00,_TBMaskedTile_0H,_TBMaskedTile_V0,_TBMaskedTile_VH ; 01110 : high-priority fringed masked normal tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00 ; 01111 : high-priority fringed masked dynamic tiles
dw _TBDynamicMaskTile_00,_TBDynamicMaskTile_00
; Here are all the sprite variants of the tiles
dw _TBSolidSpriteTile_00,_TBSolidSpriteTile_0H,
dw _TBSolidSpriteTile_V0,_TBSolidSpriteTile_VH ; 10000 : normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10001 : dynamic tiles w/sprite
dw _TBMaskedSpriteTile_00,_TBMaskedSpriteTile_0H,
dw _TBMaskedSpriteTile_V0,_TBMaskedSpriteTile_VH ; 10010 : masked normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10011 : masked dynamic tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10100 : fringed normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10101 : fringed dynamic tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10110 : fringed masked normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 10111 : fringed masked dynamic tiles w/sprite
dw _TBSolidPrioritySpriteTile_00,_TBSolidPrioritySpriteTile_0H,
dw _TBSolidPrioritySpriteTile_V0,_TBSolidPrioritySpriteTile_VH ; 11000 : high-priority normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11001 : high-priority dynamic tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11010 : high-priority masked normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11011 : high-priority masked dynamic tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11100 : high-priority fringed normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11101 : high-priority fringed dynamic tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11110 : high-priority fringed masked normal tiles w/sprite
dw _TBSolidTile_00,_TBSolidTile_0H,_TBSolidTile_V0,_TBSolidTile_VH ; 11111 : high-priority fringed masked dynamic tiles w/sprite
; _TBConstTile
;
; A specialized routine that fills in a tile with a single constant value. It's intended to be used to
; fill in solid colors, so there are no specialized horizontal or verical flipped variants
_TBConstTile
sta: $0001,y
sta: $0004,y
sta $1001,y
sta $1004,y
sta $2001,y
sta $2004,y
sta $3001,y
sta $3004,y
sta $4001,y
sta $4004,y
sta $5001,y
sta $5004,y
sta $6001,y
sta $6004,y
sta $7001,y
sta $7004,y
jmp _TBFillPEAOpcode
ClearTile
and #$00FF
ora #$4800
sta: $0004,y
sta $1004,y
sta $2004,y
sta $3004,y
sta $4004,y
sta $5004,y
sta $6004,y
sta $7004,y
inc
inc
sta: $0001,y
sta $1001,y
sta $2001,y
sta $3001,y
sta $4001,y
sta $5001,y
sta $6001,y
sta $7001,y
sep #$20
lda #$B1 ; This is a special case where we can set all the words to LDA (DP),y
sta: $0000,y
sta: $0003,y
sta $1000,y
sta $1003,y
sta $2000,y
sta $2003,y
sta $3000,y
sta $3003,y
sta $4000,y
sta $4003,y
sta $5000,y
sta $5003,y
sta $6000,y
sta $6003,y
sta $7000,y
sta $7003,y
rep #$20
rts
; Helper functions to copy tile data to the appropriate location in Bank 0
; X = tile ID
; Y = dynamic tile ID
CopyTileToDyn ENT
txa
jsr _GetTileAddr
tax
tya
and #$001F ; Maximum of 32 dynamic tiles
asl
asl ; 4 bytes per page
adc BlitterDP ; Add to the bank 00 base address
adc #$0100 ; Go to the next page
tay
jsr CopyTileDToDyn ; Copy the tile data
jsr CopyTileMToDyn ; Copy the tile mask
rtl
; X = address of tile
; Y = tile address in bank 0
CopyTileDToDyn
phb
pea $0000
plb
plb
ldal tiledata+0,x
sta: $0000,y
ldal tiledata+2,x
sta: $0002,y
ldal tiledata+4,x
sta $0100,y
ldal tiledata+6,x
sta $0102,y
ldal tiledata+8,x
sta $0200,y
ldal tiledata+10,x
sta $0202,y
ldal tiledata+12,x
sta $0300,y
ldal tiledata+14,x
sta $0302,y
ldal tiledata+16,x
sta $0400,y
ldal tiledata+18,x
sta $0402,y
ldal tiledata+20,x
sta $0500,y
ldal tiledata+22,x
sta $0502,y
ldal tiledata+24,x
sta $0600,y
ldal tiledata+26,x
sta $0602,y
ldal tiledata+28,x
sta $0700,y
ldal tiledata+30,x
sta $0702,y
plb
rts
; Helper function to copy tile mask to the appropriate location in Bank 0
;
; X = address of tile
; Y = tile address in bank 0
;
; Argument are the same as CopyTileDToDyn, the code takes care of adjust offsets.
; This make is possible to call the two functions back-to-back
;
; ldx tileAddr
; ldy dynTileAddr
; jsr CopyTileDToDyn
; jsr CopyTileMToDyn
CopyTileMToDyn
phb
pea $0000
plb
plb
ldal tiledata+32+0,x
sta: $0080,y
ldal tiledata+32+2,x
sta: $0082,y
ldal tiledata+32+4,x
sta $0180,y
ldal tiledata+32+6,x
sta $0182,y
ldal tiledata+32+8,x
sta $0280,y
ldal tiledata+32+10,x
sta $0282,y
ldal tiledata+32+12,x
sta $0380,y
ldal tiledata+32+14,x
sta $0382,y
ldal tiledata+32+16,x
sta $0480,y
ldal tiledata+32+18,x
sta $0482,y
ldal tiledata+32+20,x
sta $0580,y
ldal tiledata+32+22,x
sta $0582,y
ldal tiledata+32+24,x
sta $0680,y
ldal tiledata+32+26,x
sta $0682,y
ldal tiledata+32+28,x
sta $0780,y
ldal tiledata+32+30,x
sta $0782,y
plb
rts
; CopyBG0Tile
;
; A low-level function that copies 8x8 tiles directly into the code field space.
;
; A = Tile ID (0 - 511)
; X = Tile column (0 - 40)
; Y = Tile row (0 - 25)
CopyBG0Tile ENT
phb
phk
plb
jsr _CopyBG0Tile
plb
rtl
_CopyBG0Tile
phb ; save the current bank
phx ; save the original x-value
pha ; save the tile ID
tya ; lookup the address of the virtual line (y * 8)
asl
asl
asl
asl ; x2 because the table contains words, not
tay
sep #$20 ; set the bank register
lda BTableHigh,y
pha ; save for a few instruction
rep #$20
txa
asl ; there are two columns per tile, so multiple by 4
asl ; asl will clear the carry bit
tax
lda BTableLow,y
sta _BASE_ADDR ; Used in masked tile renderer
clc
adc Col2CodeOffset+2,x ; Get the right edge (which is the lower physical address)
tay
plb ; set the bank
pla ; pop the tile ID
; jsr _RenderTile
:exit
plx ; pop the x-register
plb ; restore the data bank and return
rts
; CopyBG1Tile
;
; A low-level function that copies 8x8 tiles directly into the BG1 data buffer.
;
; A = Tile ID (0 - 511)
; X = Tile column (0 - 40)
; Y = Tile row (0 - 25)
CopyBG1Tile
phb
phk
plb
jsr _CopyBG1Tile
plb
rtl
_CopyBG1Tile
phb ; save the current bank
phx ; save the original x-value
pha ; save the tile ID
tya ; lookup the address of the virtual line (y * 8)
asl
asl
asl
asl
tay
txa
asl
asl ; 4 bytes per tile column
clc
adc BG1YTable,y
tay
sep #$20
lda BG1DataBank
pha
plb ; set the bank
rep #$20
pla ; pop the tile ID
jsr _RenderTileBG1
plx ; pop the x-register
plb ; restore the data bank and return
rts
; Tile Store that holds tile records which contain all the essential information for rendering
; a tile.
;
; TileStore+TS_TILE_ID : Tile descriptor
; TileStore+TS_DIRTY : $FFFF is clean, otherwise stores a back-reference to the DirtyTiles array
; TileStore+TS_SPRITE_FLAG : Set to TILE_SPRITE_BIT if a sprite is present at this tile location
; TileStore+TS_SPRITE_ADDR ; Address of the tile in the sprite plane
; TileStore+TS_TILE_ADDR : Address of the tile in the tile data buffer
; TileStore+TS_CODE_ADDR_LOW : Low word of the address in the code field that receives the tile
; TileStore+TS_CODE_ADDR_HIGH : High word of the address in the code field that receives the tile
; TileStore+TS_WORD_OFFSET : Logical number of word for this location
; TileStore+TS_BASE_ADDR : Copy of BTableAddrLow
TileStore ENT
ds TILE_STORE_SIZE*10
; A list of dirty tiles that need to be updated in a given frame
DirtyTileCount ds 2
DirtyTiles ds TILE_STORE_SIZE ; At most this many tiles can possibly be update at once
; Initialize the tile storage data structures. This takes care of populating the tile records with the
; appropriate constant values.
InitTiles
:col equ tmp0
:row equ tmp1
; Fill in the TileStoreYTable. This is just a table of offsets into the Tile Store for each row. There
; are 26 rows with a stride of 41
ldy #0
lda #0
:yloop
sta TileStoreYTable,y
clc
adc #41*2
iny
iny
cpy #26*2
bcc :yloop
; Next, initialize the Tile Store itself
ldx #TILE_STORE_SIZE-2
lda #25
sta :row
lda #40
sta :col
:loop
; The first set of values in the Tile Store are changed during each frame based on the actions
; that are happening
stz TileStore+TS_TILE_ID,x ; clear the tile store with the special zero tile
stz TileStore+TS_TILE_ADDR,x
stz TileStore+TS_SPRITE_FLAG,x ; no sprites are set at the beginning
lda #$FFFF ; none of the tiles are dirty
sta TileStore+TS_DIRTY,x
; The next set of values are constants that are simply used as cached parameters to avoid needing to
; calculate any of these values during tile rendering
lda :row ; Set the long address of where this tile
asl ; exists in the code fields
tay
lda BRowTableHigh,y
sta TileStore+TS_CODE_ADDR_HIGH,x ; High word of the tile address (just the bank)
lda BRowTableLow,y
sta TileStore+TS_BASE_ADDR,x ; May not be needed later if we can figure out the right constant...
lda :col ; Set the offset values based on the column
asl ; of this tile
asl
sta TileStore+TS_WORD_OFFSET,x ; This is the offset from 0 to 82, used in LDA (dp),y instruction
tay
lda Col2CodeOffset+2,y
clc
adc TileStore+TS_BASE_ADDR,x
sta TileStore+TS_CODE_ADDR_LOW,x ; Low word of the tile address in the code field
dec :col
bpl :hop
dec :row
lda #40
sta :col
:hop
dex
dex
bpl :loop
rts
_ClearDirtyTiles
bra :hop
:loop
jsr _PopDirtyTile
:hop
lda DirtyTileCount
bne :loop
rts
; Helper function to get the address offset into the tile cachce / tile backing store
; X = tile column [0, 40] (41 columns)
; Y = tile row [0, 25] (26 rows)
GetTileStoreOffset ENT
phb
phk
plb
jsr _GetTileStoreOffset
plb
rtl
_GetTileStoreOffset
phx ; preserve the registers
phy
jsr _GetTileStoreOffset0
ply
plx
rts
_GetTileStoreOffset0
tya
asl
tay
txa
asl
clc
adc TileStoreYTable,y
rts
; Set a tile value in the tile backing store. Mark dirty if the value changes
;
; A = tile id
; X = tile column [0, 40] (41 columns)
; Y = tile row [0, 25] (26 rows)
_SetTile
pha
jsr _GetTileStoreOffset0 ; Get the address of the X,Y tile position
tay
pla
cmp TileStore+TS_TILE_ID,y ; Only set to dirty if the value changes
beq :nochange
sta TileStore+TS_TILE_ID,y ; Value is different, store it.
jsr _GetTileAddr
sta TileStore+TS_TILE_ADDR,y ; Committed to drawing this tile, so get the address of the tile in the tiledata bank for later
tya ; Add this tile to the list of dirty tiles to refresh
jmp _PushDirtyTile ; on the next call to _ApplyTiles
:nochange rts
; Append a new dirty tile record
;
; A = result of _GetTileStoreOffset for X, Y
;
; The main purpose of this function is to
;
; 1. Avoid marking the same tile dirty multiple times, and
; 2. Pre-calculating all of the information necessary to render the tile
PushDirtyTile ENT
phb
phk
plb
jsr _PushDirtyTile
plb
rtl
_PushDirtyTileOld
tay ; check if this already marked immediately
lda TileStore+TS_DIRTY,y ; If the lookup === $FFFF (<$8000), it is free.
bpl :occupied
; At this point, keep the Y register value because it is the correct offset to all of the tile
; record fields.
ldx DirtyTileCount
txa
sta TileStore+TS_DIRTY,y ; Store a back-link to this record
tya
sta DirtyTiles,x ; Store the lookup address in the list
inx
inx
stx DirtyTileCount ; Commit
:occupied
rts
; alternate version that is very slightly slower, but preserves the y-register
_PushDirtyTile
tax
; alternate entry point if the x-register is already set
_PushDirtyTileX
lda TileStore+TS_DIRTY,x
bpl :occupied2
lda DirtyTileCount
sta TileStore+TS_DIRTY,x
pha ; Would be nice to have an "exchange a and x" instruction
txa
plx
sta DirtyTiles,x
inx
inx
stx DirtyTileCount
rts
:occupied2
txa ; Make sure TileStore offset is returned in the accumulator
rts
; Remove a dirty tile from the list and return it in state ready to be rendered. It is important
; that the core rendering functions *only* use _PopDirtyTile to get a list of tiles to update,
; because this routine merges the tile IDs stored in the Tile Store with the Sprite
; information to set the TILE_SPRITE_BIT. This is the *only* place in the entire code base that
; applies this bit to a tile descriptor.
PopDirtyTile ENT
phb
phk
plb
jsr _PopDirtyTile
plb
rtl
_PopDirtyTile
ldx DirtyTileCount
bne _PopDirtyTile2
rts
_PopDirtyTile2 ; alternate entry point
dex
dex
stx DirtyTileCount ; remove last item from the list
ldy DirtyTiles,x ; load the offset into the Tile Store
lda #$FFFF
sta TileStore+TS_DIRTY,y ; clear the occupied backlink
rts
; Run through the dirty tile list and render them into the code field
ApplyTiles ENT
phb
phk
plb
jsr _ApplyTiles
plb
rtl
_ApplyTiles
bra :begin
:loop
; Retrieve the offset of the next dirty Tile Store items in the Y-register
jsr _PopDirtyTile2
; Call the generic dispatch with the Tile Store record pointer at by the Y-register.
phb
jsr _RenderTile2
plb
; Loop again until the list of dirty tiles is empty
:begin ldx DirtyTileCount
bne :loop
rts
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