diff --git a/Makefile b/Makefile
index 86351e37..be34b92b 100644
--- a/Makefile
+++ b/Makefile
@@ -86,34 +86,8 @@ endif
 
 # Clear the default suffixes
 .SUFFIXES:
-
-# Don't delete generated art and audio between builds. These are intermediates:
-# nothing names them as a target, they are only pulled in as scaninc-discovered
-# prerequisites of the object rules, so make would remove them after each build.
-#
-# This list is deliberately scoped rather than a bare `.SECONDARY:`. A bare one
-# marks *every* target secondary, including $(OBJS), and make does not rebuild a
-# missing secondary file when whatever depends on it still looks up to date --
-# so deleting an object and re-running `make compare` relinked a stale ELF and
-# printed OK without rebuilding anything. Objects must stay non-secondary for a
-# missing .o to force a rebuild.
-#
-# .PRECIOUS with patterns would be terser but it defeats .DELETE_ON_ERROR, which
-# would leave a half-written .4bpp in place after a failed conversion and
-# silently produce a wrong ROM.
-GFX_PNG_SRCS := $(shell find graphics -type f -name '*.png')
-GFX_PAL_SRCS := $(shell find graphics -type f -name '*.pal')
-SND_WAV_SRCS := $(shell find sound -type f -name '*.wav')
-
-SECONDARY_ASSETS := $(GFX_PNG_SRCS:.png=.4bpp) $(GFX_PNG_SRCS:.png=.8bpp) \
-                    $(GFX_PNG_SRCS:.png=.1bpp) $(GFX_PNG_SRCS:.png=.gbapal) \
-                    $(GFX_PAL_SRCS:.pal=.gbapal)
-SECONDARY_ASSETS += $(addsuffix .lz,$(SECONDARY_ASSETS)) \
-                    $(addsuffix .rl,$(SECONDARY_ASSETS)) \
-                    $(SND_WAV_SRCS:.wav=.bin)
-
-.SECONDARY: $(SECONDARY_ASSETS)
-
+# Don't delete intermediate files
+.SECONDARY:
 # Delete files that weren't built properly
 .DELETE_ON_ERROR:
 
diff --git a/data/board_data/VRAM_LAYOUT.md b/data/board_data/VRAM_LAYOUT.md
deleted file mode 100644
index 519331b3..00000000
--- a/data/board_data/VRAM_LAYOUT.md
+++ /dev/null
@@ -1,172 +0,0 @@
-# Main-field board BG VRAM layout
-
-How the scrolling pinball board is assembled in VRAM. Worked out for FIELD_RUBY;
-the other main fields use the same shape with their own assets.
-
-Without this, the board tile sheets cannot be read as pictures: the tilemaps
-index a window that is streamed at runtime, so any static interpretation of
-char base 2 produces a recognisable-but-corrupted board.
-
-## BG configuration
-
-From `SetupDisplayRegistersForField` (`src/all_board_pinball_game_main.c:178`),
-FIELD_RUBY. Screen base N is `VRAM + N*0x800`, char base N is `VRAM + N*0x4000`.
-
-| BG  | screen base | char base | size  | priority | tilemap source                            |
-|-----|-------------|-----------|-------|----------|-------------------------------------------|
-| BG0 | 4           | 1         | 32x64 | 0        | built at runtime in `gBG0TilemapBuffer`   |
-| BG1 | 6           | 2         | 32x64 | 1        | `gRubyBoardBGTilemap`                     |
-| BG2 | 2           | 1         | 32x64 | 2        | `gRubyBoardBG1Tilemap` (ramp)             |
-| BG3 | 0           | 2         | 32x64 | 3        | `gRubyBoardBG0Tilemap`                    |
-
-Note the labels do not match the layers: `gRubyBoardBG0Tilemap` is DMA'd to
-screen base 0, which is **BG3**, and `gRubyBoardBG1Tilemap` to screen base 2,
-which is **BG2**.
-
-## Char base 1 (BG0, BG2)
-
-`loadFieldBoardGraphics` decompresses `gRubyBoardCompressedTiles1` (the bgramp
-sheet) and copies its first 0x4000 bytes -- 512 tiles -- over the whole
-charblock. BG2's tilemap only reaches id 223, well inside that.
-
-## Char base 2 (BG1, BG3) -- the part that matters
-
-Two regions with completely different lifetimes:
-
-    tiles 0-703     streamed ring window, rewritten as the board scrolls
-    tiles 704-1023  gRubyBoardBGTiles, static overlay (rails, ramps, SHOP sign)
-
-`loadFieldBoardGraphics` appears to place bgtop into tiles 0-703 with two
-DmaCopy16 calls, but those are immediately superseded: the caller in
-`src/save_and_restore_game.c:213` runs a streaming loop afterwards.
-
-### The ring
-
-    for (i = 0; i < 22; i++) {
-        var0 = i + scroll;
-        var1 = (i + 10 + scroll) % 22;
-        src  = var0 < 32 ? &gBoardGfxBuffer[var0 * 0x400]          // bgtop
-                         : &gBoardBGTileBufferAlt[(var0-32) * 0x400]; // bgbottom
-        DmaCopy16(3, src, (void *)0x6008000 + var1 * 0x400, 0x400);
-    }
-
-A chunk is `0x400` bytes = 32 tiles = exactly one row of the 32-tile-wide board.
-The source is a virtual 64-chunk strip: bgtop supplies chunks 0-31, bgbottom
-chunks 32-63. 22 of those 64 rows are resident at a time.
-
-Substituting `i = C - scroll` for chunk `C` gives slot `(C + 10) % 22`: **a chunk
-always lands in the same slot regardless of scroll position.** That invariant is
-what makes the sheets statically reconstructible.
-
-## Reconstructing the board
-
-Because chunk == tilemap row, BG3's tilemap row `R` always draws chunk `R`:
-
-    tile pixels for (row R, column c)
-        = (bgtop ++ bgbottom)[ R*32 + (tilemap_id % 32) ]
-
-with the entry's own flip bits and palette bank applied as usual.
-
-Verified against `ruby_board_bg0_tilemap.bin`: 57 of 64 rows have every tile id
-inside slot `(R+10) % 22` exactly as predicted. The 7 exceptions are rows 56-63,
-which are filler -- every entry is 0. So the board proper is rows 0-55, i.e.
-256x448 pixels.
-
-## Palette
-
-`loadFieldBoardGraphics` copies `BG_PLTT_SIZE` (0x200) from `gRubyBoardPalette`,
-which is only 0x180 long, so banks 12-15 come from whatever follows it in ROM.
-The tilemaps do use bank 13, so a faithful render needs the full 0x200 read.
-
-## Which boards this applies to
-
-The streaming loop is gated on `gMain.selectedField < MAIN_FIELD_COUNT`, and
-`MAIN_FIELD_COUNT` is 2 (`include/constants/fields.h:6`). So **only Ruby and
-Sapphire scroll**, and they share an identical BG configuration -- the model
-above transfers to Sapphire unchanged.
-
-The six bonus boards are static: no ring, no scroll, char base 2 is simply what
-`loadFieldBoardGraphics` leaves there. Dusclops is representative:
-
-    LZ77UnCompWram(gBonusFieldCompressedBaseTiles, gBoardGfxBuffer);
-    DmaCopy16(3, gBoardGfxBuffer, (void *)0x06004000, 0x4000);   // char base 1, shared
-    LZ77UnCompWram(gDusclopsBoardCompressedBGTiles, gBoardGfxBuffer);
-    DmaCopy16(3, gBoardGfxBuffer, (void *)0x06008000, 0x8000);   // char base 2, 1024 tiles
-    DmaCopy16(3, gDusclopsBoardBG0Tilemap, (void *)0x06000000, 0x800);  // BG3
-    DmaCopy16(3, gDusclopsBoardBG1Tilemap, (void *)0x06000800, 0x800);  // BG2
-    DmaCopy16(3, gDusclopsBoardBG2Tilemap, (void *)0x06001000, 0x800);  // BG1
-
-All three of its BG layers read char base 2, and each tilemap is a plain 32x32
-screen, so those boards fold with `detilemap` directly -- no ring reconstruction.
-Note char base 1 holds `gBonusFieldCompressedBaseTiles`, which is shared by every
-bonus board.
-
-Per-field BG configuration (screen base / char base / size):
-
-| field    | BG0        | BG1        | BG2        | BG3        |
-|----------|------------|------------|------------|------------|
-| RUBY     | 4/1 32x64  | 6/2 32x64  | 2/1 32x64  | 0/2 32x64  |
-| SAPPHIRE | 4/1 32x64  | 6/2 32x64  | 2/1 32x64  | 0/2 32x64  |
-| DUSCLOPS | 4/1 32x64  | 2/2 32x32  | 1/2 32x32  | 0/2 32x32  |
-| KECLEON  | 4/1 32x64  | 2/2 32x32  | 1/2 32x32  | 0/2 32x32  |
-| KYOGRE   | 4/1 32x64  | --         | 1/2 32x32  | 0/2 32x32  |
-| GROUDON  | 4/1 32x64  | --         | 1/2 32x32  | 0/2 32x32  |
-| RAYQUAZA | 4/1 32x64  | 6/2 32x64  | 2/2 32x64  | 0/2 32x64  |
-| SPHEAL   | 4/1 32x64  | 2/2 32x64  | 1/2 32x32  | 0/2 32x32  |
-
-## OBJ tiles and the OBJ palette
-
-`loadFieldBoardGraphics` ends every field with one 0x8000 DMA of the board's
-`intro_sprite` sheet to 0x06010000, so OAM tile number 0 is tile 0 of that
-sheet and the tile ranges quoted in the sprite-set data index it directly.
-The sheets are shorter than the 1024 tiles the region holds; the tail is left
-over from whatever ran before.
-
-Much of the region is scratch, streamed over frame by frame from a table of
-interchangeable art. The art checked in at those offsets is only what the sheet
-happens to ship with, and its palette arrives with the replacement tiles rather
-than sitting in the board's own set:
-
-| tiles | written by | palette |
-|-------|------------|---------|
-| 0x65  | `all_board_portrait_display.c` (portrait slot 0) | into the bank `gPortraitPaletteSlots[0]` names, 13 |
-| 0x7d  | `all_board_portrait_display.c` (portrait slot 1) | `gLocationPalettes[n]`, into bank 12 |
-| 0x95  | `main_board_pichu_entity.c`, `gMonHatchSpriteGroup5_Gfx` | mon hatch group palette |
-| 0xb6  | `main_board_evolution_mode.c`, `gEvoItemTilesGfxPtrs[n]` | `gEvoItemPalettes[n]`, into bank 15 |
-| 0x107 | `main_board_launcher_and_cutscenes.c`, `gSpoinkEntity_Gfx` | bank 11, see below |
-| 0x115 | `main_board_to_be_split.c`, `gRubyBoardHatchCave_Gfx` | bank 11, see below |
-| 0x1e8 | `UpdateRubyEvolutionShopSprite`, `gRubyBoardShop_Gfx` | `gShopPalette`, into bank 2 |
-| 0x295 | `DrawOneUpBannerSprite`, `gOneUpBannerSprite_Gfx` | `gOneUpSpritePalette`, into bank 12 |
-
-Which entry of each table the sheet ships is recoverable by searching the ROM
-for the segment's own tiles: tile 0x7d is `gLocationPortraitGfx[0]` and tile
-0x95 is `wurmple_hatch` frame 0, both byte-identical, and tile 0xb6 is
-`gPickupIcon1_Gfx`. Tile 0x65 is a Geodude portrait close to but not identical
-to the extracted one.
-
-OBJ bank 11 is never its resting ROM value on the main fields: `UpdateSpoinkAnimation`
-runs every frame and rewrites it from `gFieldPaletteVariants[field][set * 2 + (camera is low)]`,
-six banks per field -- three brightness sets crossed with which half of the
-board is on screen. Set 0 is what plays, so the upper half of the board is
-variant 0 (ruby) / 6 (sapphire) and the lower half 1 / 7. Spoink is the plunger
-at the bottom; the egg, hatch cave and hatch machine sit at the top. Ruby's
-resting value for the bank happens to equal its own upper-half variant.
-
-The OBJ palette itself is one 512-byte DMA:
-
-    DmaCopy16(3, gBoardConfig.fieldLayout.objPaletteSets[0], (void *)OBJ_PLTT, OBJ_PLTT_SIZE);
-
-`objPaletteSets[1]` and `[2]` are the same palette at two dimmer levels, used
-by the banner fades in `all_board_banners.c`; set 0 is the one on screen during
-play. Every board's set 0 is a full 512 bytes except ruby's, which is 0x120 --
-the DMA runs on past it into `gBonusStageObjPal`, so ruby's OBJ banks 0-8 come
-from `ruby_board_palset_0.gbapal` and banks 9-15 from
-`graphics/stage/main/bonus_stage_obj.gbapal`. The bonus boards copy that same
-label's first bank to 0x05000320, which is OBJ bank 9 there too.
-
-Sapphire leaves banks 12-15 at zero and loads them when the sprites that use
-them appear; ruby, by the overlap above, keeps a usable copy in ROM.
-
-`tools/scripts/objpalette.py` derives which bank each segment of a sheet is
-drawn with from the OAM data in `data/rom_2.s`, records it in the gfx config as
-`"palette"`/`"palbank"`, and recolours the segment PNGs to match.
diff --git a/graphics/intro/scene1torchic/bg1_dividers_screen.png b/graphics/intro/scene1torchic/bg1_dividers_screen.png
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diff --git a/graphics/intro/scene2pikas/bg0_pichu_screen.png b/graphics/intro/scene2pikas/bg0_pichu_screen.png
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diff --git a/graphics/intro/scene3treecko/bg0_treecko_screen.png b/graphics/intro/scene3treecko/bg0_treecko_screen.png
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diff --git a/graphics/intro/scene4plussleminun/bg0_minun_screen.png b/graphics/intro/scene4plussleminun/bg0_minun_screen.png
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diff --git a/graphics/intro/scene4plussleminun/bg1_plussle_screen.png b/graphics/intro/scene4plussleminun/bg1_plussle_screen.png
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diff --git a/graphics/intro/scene4plussleminun/bg3_text_screen.png b/graphics/intro/scene4plussleminun/bg3_text_screen.png
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diff --git a/graphics/intro/scene4plussleminun/intro_gfx.json b/graphics/intro/scene4plussleminun/intro_gfx.json
new file mode 100644
index 00000000..3b7cd985
--- /dev/null
+++ b/graphics/intro/scene4plussleminun/intro_gfx.json
@@ -0,0 +1,30 @@
+{
+  "kind": "gfx-config",
+  "version": 1,
+  "defaults": {
+    "mwidth": 0,
+    "mheight": 0,
+    "oam": false,
+    "width": 16,
+    "palette": ""
+  },
+  "files": [
+    {
+      "gfx_filename": "tiles",
+      "segments":[
+        {
+            "segfile": "text_tiles",
+            "width":20
+        },
+        {
+            "segfile": "space_tiles"
+        },
+        {
+            "segfile": "mon_tiles",
+            "width":24
+        }
+      ],
+      "align":1
+    }
+  ]
+}
\ No newline at end of file
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diff --git a/graphics/intro/scene8wailmerlaunch/tiles_unmapped.png b/graphics/intro/scene8wailmerlaunch/tiles_unmapped.png
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index a24467d0..00000000
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diff --git a/graphics/stage/rayquaza/rayquaza_board_bg0_screen.png b/graphics/stage/rayquaza/rayquaza_board_bg0_screen.png
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diff --git a/graphics/stage/rayquaza/rayquaza_board_scroll_screen.png b/graphics/stage/rayquaza/rayquaza_board_scroll_screen.png
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diff --git a/graphics/stage/ruby/ruby_board_bg_screen.png b/graphics/stage/ruby/ruby_board_bg_screen.png
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diff --git a/graphics/stage/sapphire/sapphire_board_bgbottom_tiles.png b/graphics/stage/sapphire/sapphire_board_bgbottom_tiles.png
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diff --git a/graphics/stage/sapphire/sapphire_board_bgramp_tiles.png b/graphics/stage/sapphire/sapphire_board_bgramp_tiles.png
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diff --git a/graphics/stage/sapphire/sapphire_board_bgtop_tiles.png b/graphics/stage/sapphire/sapphire_board_bgtop_tiles.png
new file mode 100644
index 00000000..ba064887
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diff --git a/graphics/stage/sapphire/sapphire_board_ramp_screen.png b/graphics/stage/sapphire/sapphire_board_ramp_screen.png
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diff --git a/graphics/stage/sapphire/sapphire_board_ramp_unmapped_a.png b/graphics/stage/sapphire/sapphire_board_ramp_unmapped_a.png
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diff --git a/graphics/stage/sapphire/sapphire_board_screen.png b/graphics/stage/sapphire/sapphire_board_screen.png
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index c87168d1..00000000
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diff --git a/graphics/stage/spheal/spheal_board_bg_screen.png b/graphics/stage/spheal/spheal_board_bg_screen.png
deleted file mode 100644
index 30b0babc..00000000
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diff --git a/graphics/stage/spheal/spheal_board_bg_tiles.png b/graphics/stage/spheal/spheal_board_bg_tiles.png
new file mode 100644
index 00000000..4ff6ceb9
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diff --git a/graphics/stage/spheal/spheal_board_bgwater_screen.png b/graphics/stage/spheal/spheal_board_bgwater_screen.png
deleted file mode 100644
index 5fd76908..00000000
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diff --git a/graphics/stage/spheal/spheal_board_unmapped.png b/graphics/stage/spheal/spheal_board_unmapped.png
deleted file mode 100644
index df5cf92e..00000000
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diff --git a/graphics_rules.mk b/graphics_rules.mk
index b69adac6..35b40123 100644
--- a/graphics_rules.mk
+++ b/graphics_rules.mk
@@ -15,286 +15,3 @@ graphics/options/sprites.4bpp: graphics/options/sprites.png
 
 graphics/pokedex/text_glyphs.4bpp: graphics/pokedex/text_glyphs.png
 	$(GFX) $< $@ -num_tiles 513
-
-# --- BG sheets rebuilt from assembled screens -------------------------------
-# These tile sheets are deduplicated, so the raw sheet is not editable as an
-# image at any width. The checked-in source is the assembled screen instead
-# (8bpp, pixel = palette bank * 16 + colour index); detilemap folds the screens
-# back down through their tilemaps. See tools/scripts/detilemap.py.
-
-PYTHON ?= python3
-DETILEMAP := $(PYTHON) tools/scripts/detilemap.py
-
-S1TORCHIC := graphics/intro/scene1torchic
-# bg0_tilemap.bin is not listed: its three screens reference only blank tiles of
-# this sheet (its artwork lives in the ball buffer, tiles 704-890), so it adds
-# no pixels here. Tiles 320-703 are unreferenced and come out as zeroes.
-$(S1TORCHIC)/tiles.4bpp: $(S1TORCHIC)/bg3_text_screen.png $(S1TORCHIC)/bg3_text_tilemap.bin \
-                         $(S1TORCHIC)/bg1_dividers_screen.png $(S1TORCHIC)/bg1_dividers_tilemap.bin \
-                         $(S1TORCHIC)/bg2_dividers_screen.png $(S1TORCHIC)/bg2_dividers_tilemap.bin \
-                         tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 704 -o $@ \
-		--from $(S1TORCHIC)/bg3_text_screen.png:$(S1TORCHIC)/bg3_text_tilemap.bin:32x32 \
-		--from $(S1TORCHIC)/bg1_dividers_screen.png:$(S1TORCHIC)/bg1_dividers_tilemap.bin:32x64 \
-		--from $(S1TORCHIC)/bg2_dividers_screen.png:$(S1TORCHIC)/bg2_dividers_tilemap.bin:32x64
-
-# Bonus boards are static: no scroll ring, and all three BG layers read char
-# base 2, so the sheet folds straight out of its three 32x32 screens.
-# See data/board_data/VRAM_LAYOUT.md.
-DUSCLOPS := graphics/stage/dusclops
-$(DUSCLOPS)/dusclops_board_bg_tiles.4bpp: \
-		$(foreach s,bg0 bg1 bg2,$(DUSCLOPS)/dusclops_board_$(s)_screen.png $(DUSCLOPS)/dusclops_board_$(s)_tilemap.bin) \
-		tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(DUSCLOPS)/dusclops_board_bg0_screen.png:$(DUSCLOPS)/dusclops_board_bg0_tilemap.bin:32x32 \
-		--from $(DUSCLOPS)/dusclops_board_bg1_screen.png:$(DUSCLOPS)/dusclops_board_bg1_tilemap.bin:32x32 \
-		--from $(DUSCLOPS)/dusclops_board_bg2_screen.png:$(DUSCLOPS)/dusclops_board_bg2_tilemap.bin:32x32
-
-KYOGRE := graphics/stage/kyogre
-# 32 non-blank tiles (water/bubble art) sit unreferenced in an 8x4 block at rows
-# 8-11, cols 4-11 of the 32-wide grid. One 32x4 strip over tiles 256-383 covers
-# them; the referenced tiles it also spans agree with the screens.
-$(KYOGRE)/kyogre_board_bg_tiles.4bpp: \
-		$(foreach s,bg0 bg1,$(KYOGRE)/kyogre_board_$(s)_screen.png $(KYOGRE)/kyogre_board_$(s)_tilemap.bin) \
-		$(KYOGRE)/kyogre_board_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(KYOGRE)/kyogre_board_bg0_screen.png:$(KYOGRE)/kyogre_board_bg0_tilemap.bin:32x32 \
-		--from $(KYOGRE)/kyogre_board_bg1_screen.png:$(KYOGRE)/kyogre_board_bg1_tilemap.bin:32x32 \
-		--extra $(KYOGRE)/kyogre_board_unmapped.png@256
-
-KECLEON := graphics/stage/kecleon
-# The four kecleon_overlay_* maps are not screens: kecleon_process3.c mines rows
-# out of gKecleonBerryOverlayTilemap into gBG0TilemapBuffer as fragments, so they
-# render as strips rather than pictures. They are still the only source for tiles
-# 640-1023, and all four contribute distinct ones, so all four are needed.
-KECLEON_MAPS := kecleon_board_bg0 kecleon_board_bg1 \
-                kecleon_overlay_0 kecleon_overlay_1 kecleon_overlay_2 kecleon_overlay_3
-$(KECLEON)/kecleon_board_bg_tiles.4bpp: \
-		$(foreach s,$(KECLEON_MAPS),$(KECLEON)/$(s)_screen.png $(KECLEON)/$(s)_tilemap.bin) \
-		tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		$(foreach s,$(KECLEON_MAPS),--from $(KECLEON)/$(s)_screen.png:$(KECLEON)/$(s)_tilemap.bin:32x32)
-
-SPHEAL := graphics/stage/spheal
-# Only two of its layers have a static tilemap; BG1's is built at runtime.
-# 32 non-blank tiles sit unreferenced in an 8x4 block at rows 17-20, cols 4-11,
-# so one 32x4 strip over tiles 544-671 carries them.
-$(SPHEAL)/spheal_board_bg_tiles.4bpp: \
-		$(SPHEAL)/spheal_board_bgwater_screen.png $(SPHEAL)/spheal_board_bgwater_tilemap.bin \
-		$(SPHEAL)/spheal_board_bg_screen.png $(SPHEAL)/spheal_board_bg_tilemap.bin \
-		$(SPHEAL)/spheal_board_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(SPHEAL)/spheal_board_bgwater_screen.png:$(SPHEAL)/spheal_board_bgwater_tilemap.bin:32x32 \
-		--from $(SPHEAL)/spheal_board_bg_screen.png:$(SPHEAL)/spheal_board_bg_tilemap.bin:32x32 \
-		--extra $(SPHEAL)/spheal_board_unmapped.png@544
-
-RAYQUAZA := graphics/stage/rayquaza
-# Three 32x64 layers, all on char base 2. Tiles 301 and 335 are non-blank but
-# referenced by no tilemap.
-RAYQUAZA_MAPS := bg0 bg1 scroll
-$(RAYQUAZA)/rayquaza_board_bg_tiles.4bpp: \
-		$(foreach s,$(RAYQUAZA_MAPS),$(RAYQUAZA)/rayquaza_board_$(s)_screen.png $(RAYQUAZA)/rayquaza_board_$(s)_tilemap.bin) \
-		$(RAYQUAZA)/rayquaza_board_unmapped_a.png $(RAYQUAZA)/rayquaza_board_unmapped_b.png \
-		tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		$(foreach s,$(RAYQUAZA_MAPS),--from $(RAYQUAZA)/rayquaza_board_$(s)_screen.png:$(RAYQUAZA)/rayquaza_board_$(s)_tilemap.bin:32x64) \
-		--extra $(RAYQUAZA)/rayquaza_board_unmapped_a.png@301 \
-		--extra $(RAYQUAZA)/rayquaza_board_unmapped_b.png@335
-
-GROUDON := graphics/stage/groudon
-$(GROUDON)/groudon_board_bg_tiles.4bpp: \
-		$(foreach s,bg0 bg1,$(GROUDON)/groudon_board_$(s)_screen.png $(GROUDON)/groudon_board_$(s)_tilemap.bin) \
-		tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(GROUDON)/groudon_board_bg0_screen.png:$(GROUDON)/groudon_board_bg0_tilemap.bin:32x32 \
-		--from $(GROUDON)/groudon_board_bg1_screen.png:$(GROUDON)/groudon_board_bg1_tilemap.bin:32x32
-
-# Sapphire shares Ruby's BG configuration and scroll ring exactly.
-SAPPHIRE := graphics/stage/sapphire
-$(SAPPHIRE)/sapphire_board_strip.4bpp: $(SAPPHIRE)/sapphire_board_screen.png \
-                                       $(SAPPHIRE)/sapphire_board_bg0_tilemap.bin \
-                                       tools/scripts/detilemap.py
-	$(DETILEMAP) extract --row-chunk 32 -n 2048 -o $@ \
-		--from $(SAPPHIRE)/sapphire_board_screen.png:$(SAPPHIRE)/sapphire_board_bg0_tilemap.bin:32x64
-
-$(SAPPHIRE)/sapphire_board_bgtop_tiles.4bpp: $(SAPPHIRE)/sapphire_board_strip.4bpp
-	head -c 32768 $< > $@
-
-$(SAPPHIRE)/sapphire_board_bgbottom_tiles.4bpp: $(SAPPHIRE)/sapphire_board_strip.4bpp
-	tail -c 32768 $< > $@
-
-# Same BG0 runtime-tilemap region as Ruby: tiles 256-318 and 416-510 are
-# unreachable statically.
-$(SAPPHIRE)/sapphire_board_bgramp_tiles.4bpp: $(SAPPHIRE)/sapphire_board_ramp_screen.png \
-		$(SAPPHIRE)/sapphire_board_bgramp_tilemap.bin \
-		$(SAPPHIRE)/sapphire_board_ramp_unmapped_a.png \
-		$(SAPPHIRE)/sapphire_board_ramp_unmapped_b.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(SAPPHIRE)/sapphire_board_ramp_screen.png:$(SAPPHIRE)/sapphire_board_bgramp_tilemap.bin:32x64 \
-		--extra $(SAPPHIRE)/sapphire_board_ramp_unmapped_a.png@256 \
-		--extra $(SAPPHIRE)/sapphire_board_ramp_unmapped_b.png@416
-
-$(SAPPHIRE)/sapphire_board_bg_tiles.4bpp: $(SAPPHIRE)/sapphire_board_bg_screen.png \
-		$(SAPPHIRE)/sapphire_board_bg_tilemap.bin \
-		$(SAPPHIRE)/sapphire_board_bg_unmapped_a.png \
-		$(SAPPHIRE)/sapphire_board_bg_unmapped_b.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(SAPPHIRE)/sapphire_board_bg_screen.png:$(SAPPHIRE)/sapphire_board_bg_tilemap.bin:32x64 \
-		--extra $(SAPPHIRE)/sapphire_board_bg_unmapped_a.png@705 \
-		--extra $(SAPPHIRE)/sapphire_board_bg_unmapped_b.png@880
-
-RUBY := graphics/stage/ruby
-
-# The board art itself. Ruby scrolls, so char base 2 holds a 22-slot ring over a
-# 64-chunk virtual strip (bgtop then bgbottom) and tilemap row R draws chunk R --
-# hence --row-chunk 32. One screen therefore reconstructs both sheets, which are
-# split back apart below. See data/board_data/VRAM_LAYOUT.md.
-$(RUBY)/ruby_board_strip.4bpp: $(RUBY)/ruby_board_screen.png $(RUBY)/ruby_board_bg0_tilemap.bin \
-                               tools/scripts/detilemap.py
-	$(DETILEMAP) extract --row-chunk 32 -n 2048 -o $@ \
-		--from $(RUBY)/ruby_board_screen.png:$(RUBY)/ruby_board_bg0_tilemap.bin:32x64
-
-$(RUBY)/ruby_board_bgtop_tiles.4bpp: $(RUBY)/ruby_board_strip.4bpp
-	head -c 32768 $< > $@
-
-$(RUBY)/ruby_board_bgbottom_tiles.4bpp: $(RUBY)/ruby_board_strip.4bpp
-	tail -c 32768 $< > $@
-
-# The ramp sheet sits at char base 1, which BG0 also reads -- but BG0's tilemap
-# is built at runtime, so tiles 256-318 and 416-510 are unreachable statically
-# and ride along as strips.
-$(RUBY)/ruby_board_bgramp_tiles.4bpp: $(RUBY)/ruby_board_ramp_screen.png \
-                                      $(RUBY)/ruby_board_ramp_tilemap.bin \
-                                      $(RUBY)/ruby_board_ramp_unmapped_a.png \
-                                      $(RUBY)/ruby_board_ramp_unmapped_b.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(RUBY)/ruby_board_ramp_screen.png:$(RUBY)/ruby_board_ramp_tilemap.bin:32x64 \
-		--extra $(RUBY)/ruby_board_ramp_unmapped_a.png@256 \
-		--extra $(RUBY)/ruby_board_ramp_unmapped_b.png@416
-
-# tile 834 is non-blank but referenced by no tilemap.
-$(RUBY)/ruby_board_bg_tiles.4bpp: $(RUBY)/ruby_board_bg_screen.png $(RUBY)/ruby_board_bg_tilemap.bin \
-                                  $(RUBY)/ruby_board_bg_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 1024 -o $@ \
-		--from $(RUBY)/ruby_board_bg_screen.png:$(RUBY)/ruby_board_bg_tilemap.bin:32x64 \
-		--extra $(RUBY)/ruby_board_bg_unmapped.png@834
-
-S9BALL := graphics/intro/scene9ballflight
-$(S9BALL)/cloud_tiles.4bpp: $(S9BALL)/bg3_clouds_screen.png $(S9BALL)/bg3_clouds_tilemap.bin \
-                            tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 288 -o $@ \
-		--from $(S9BALL)/bg3_clouds_screen.png:$(S9BALL)/bg3_clouds_tilemap.bin:32x32
-
-S8WAIL := graphics/intro/scene8wailmerlaunch
-# tiles 376-394 are non-blank; only 383 of them is reachable through the tilemap,
-# so the whole run rides along as a strip (383 agrees with the screen).
-$(S8WAIL)/explosion_tiles.4bpp: $(S8WAIL)/bg2_explosion_screen.png $(S8WAIL)/bg2_explosion_tilemap.bin \
-                               $(S8WAIL)/tiles_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 416 -o $@ \
-		--from $(S8WAIL)/bg2_explosion_screen.png:$(S8WAIL)/bg2_explosion_tilemap.bin:32x32 \
-		--extra $(S8WAIL)/tiles_unmapped.png@376
-
-S7PARADE := graphics/intro/scene7parade
-# tile 590 is non-blank but referenced by no tilemap.
-S7SCREENS := bg3_text bg0_pelipper bg1_spoink bg2_makuhita
-$(S7PARADE)/tiles.4bpp: $(foreach s,$(S7SCREENS),$(S7PARADE)/$(s)_screen.png $(S7PARADE)/$(s)_tilemap.bin) \
-                        $(S7PARADE)/tiles_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 640 -o $@ \
-		--from $(S7PARADE)/bg3_text_screen.png:$(S7PARADE)/bg3_text_tilemap.bin:32x32 \
-		--from $(S7PARADE)/bg0_pelipper_screen.png:$(S7PARADE)/bg0_pelipper_tilemap.bin:64x64 \
-		--from $(S7PARADE)/bg1_spoink_screen.png:$(S7PARADE)/bg1_spoink_tilemap.bin:64x64 \
-		--from $(S7PARADE)/bg2_makuhita_screen.png:$(S7PARADE)/bg2_makuhita_tilemap.bin:64x64 \
-		--extra $(S7PARADE)/tiles_unmapped.png@590
-
-S6CHIN := graphics/intro/scene6chinchou
-# tiles 376-394 are non-blank but referenced by no tilemap, so they ride along
-# as a 19-tile strip rather than being zeroed.
-S6SCREENS := bg3_burst bg0_chinchou bg2_chinchou bg1_ball
-$(S6CHIN)/tiles.4bpp: $(foreach s,$(S6SCREENS),$(S6CHIN)/$(s)_screen.png $(S6CHIN)/$(s)_tilemap.bin) \
-                      $(S6CHIN)/tiles_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 800 -o $@ \
-		--from $(S6CHIN)/bg3_burst_screen.png:$(S6CHIN)/bg3_burst_tilemap.bin:32x32 \
-		--from $(S6CHIN)/bg0_chinchou_screen.png:$(S6CHIN)/bg0_chinchou_tilemap.bin:32x32 \
-		--from $(S6CHIN)/bg2_chinchou_screen.png:$(S6CHIN)/bg2_chinchou_tilemap.bin:32x32 \
-		--from $(S6CHIN)/bg1_ball_screen.png:$(S6CHIN)/bg1_ball_tilemap.bin:64x64 \
-		--extra $(S6CHIN)/tiles_unmapped.png@376
-
-S5MUDKIP := graphics/intro/scene5mudkip
-S5SCREENS := bg3_text bg0 bg1_1sections bg2_2sections
-$(S5MUDKIP)/text_tiles.4bpp: $(foreach s,$(S5SCREENS),$(S5MUDKIP)/$(s)_screen.png $(S5MUDKIP)/$(s)_tilemap.bin) \
-                             tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 640 -o $@ \
-		--from $(S5MUDKIP)/bg3_text_screen.png:$(S5MUDKIP)/bg3_text_tilemap.bin:32x32 \
-		--from $(S5MUDKIP)/bg0_screen.png:$(S5MUDKIP)/bg0_tilemap.bin:32x32 \
-		--from $(S5MUDKIP)/bg1_1sections_screen.png:$(S5MUDKIP)/bg1_1sections_tilemap.bin:32x64 \
-		--from $(S5MUDKIP)/bg2_2sections_screen.png:$(S5MUDKIP)/bg2_2sections_tilemap.bin:32x64
-
-S4PLUSMIN := graphics/intro/scene4plussleminun
-# 513 tiles, not 512: the old segmented rule appended one blank tile via
-# "align": 1, and tile 512 is that padding.
-$(S4PLUSMIN)/tiles.4bpp: $(S4PLUSMIN)/bg3_text_screen.png $(S4PLUSMIN)/bg3_text_tilemap.bin \
-                         $(S4PLUSMIN)/bg0_minun_screen.png $(S4PLUSMIN)/bg0_minun_tilemap.bin \
-                         $(S4PLUSMIN)/bg1_plussle_screen.png $(S4PLUSMIN)/bg1_plussle_tilemap.bin \
-                         tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 513 -o $@ \
-		--from $(S4PLUSMIN)/bg3_text_screen.png:$(S4PLUSMIN)/bg3_text_tilemap.bin:32x32 \
-		--from $(S4PLUSMIN)/bg0_minun_screen.png:$(S4PLUSMIN)/bg0_minun_tilemap.bin:64x64 \
-		--from $(S4PLUSMIN)/bg1_plussle_screen.png:$(S4PLUSMIN)/bg1_plussle_tilemap.bin:64x64
-
-S3TRECK := graphics/intro/scene3treecko
-# tile 303 sits in the gap between bg3's range (ends 302) and bg2's (starts 304)
-# and is referenced by no tilemap, so it is carried as a one-tile strip.
-S3SCREENS := bg3_text bg2 bg0_treecko bg1_ball bg1_ballandflipper bg1_ballflipperhit
-$(S3TRECK)/tiles.4bpp: $(foreach s,$(S3SCREENS),$(S3TRECK)/$(s)_screen.png $(S3TRECK)/$(s)_tilemap.bin) \
-                       $(S3TRECK)/tiles_unmapped.png tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 864 -o $@ \
-		--from $(S3TRECK)/bg3_text_screen.png:$(S3TRECK)/bg3_text_tilemap.bin:32x32 \
-		--from $(S3TRECK)/bg2_screen.png:$(S3TRECK)/bg2_tilemap.bin:32x64 \
-		--from $(S3TRECK)/bg0_treecko_screen.png:$(S3TRECK)/bg0_treecko_tilemap.bin:32x64 \
-		--from $(S3TRECK)/bg1_ball_screen.png:$(S3TRECK)/bg1_ball_tilemap.bin:32x32 \
-		--from $(S3TRECK)/bg1_ballandflipper_screen.png:$(S3TRECK)/bg1_ballandflipper_tilemap.bin:32x32 \
-		--from $(S3TRECK)/bg1_ballflipperhit_screen.png:$(S3TRECK)/bg1_ballflipperhit_tilemap.bin:32x32 \
-		--extra $(S3TRECK)/tiles_unmapped.png@303
-
-S2PIKAS := graphics/intro/scene2pikas
-$(S2PIKAS)/tiles.4bpp: $(S2PIKAS)/bg3_text_screen.png $(S2PIKAS)/bg3_text_tilemap.bin \
-                       $(S2PIKAS)/bg0_pichu_screen.png $(S2PIKAS)/bg0_pichu_tilemap.bin \
-                       $(S2PIKAS)/bg1_pikachu_screen.png $(S2PIKAS)/bg1_pikachu_tilemap.bin \
-                       tools/scripts/detilemap.py
-	$(DETILEMAP) extract -n 512 -o $@ \
-		--from $(S2PIKAS)/bg3_text_screen.png:$(S2PIKAS)/bg3_text_tilemap.bin:32x32 \
-		--from $(S2PIKAS)/bg0_pichu_screen.png:$(S2PIKAS)/bg0_pichu_tilemap.bin:64x64 \
-		--from $(S2PIKAS)/bg1_pikachu_screen.png:$(S2PIKAS)/bg1_pikachu_tilemap.bin:64x64
-
-# Sheets built by detilemap have no .png source, so the Makefile's
-# SECONDARY_ASSETS list -- which is derived from png/pal/wav sources -- does not
-# cover them or their .lz derivatives, and make deletes those as intermediates
-# after every build. .SECONDARY accumulates, so listing them here is enough.
-DETILEMAP_SHEETS := \
-	$(S1TORCHIC)/tiles.4bpp \
-	$(S2PIKAS)/tiles.4bpp \
-	$(S3TRECK)/tiles.4bpp \
-	$(S4PLUSMIN)/tiles.4bpp \
-	$(S5MUDKIP)/text_tiles.4bpp \
-	$(S6CHIN)/tiles.4bpp \
-	$(S7PARADE)/tiles.4bpp \
-	$(S8WAIL)/explosion_tiles.4bpp \
-	$(S9BALL)/cloud_tiles.4bpp \
-	$(RUBY)/ruby_board_bg_tiles.4bpp \
-	$(DUSCLOPS)/dusclops_board_bg_tiles.4bpp \
-	$(GROUDON)/groudon_board_bg_tiles.4bpp \
-	$(KECLEON)/kecleon_board_bg_tiles.4bpp \
-	$(KYOGRE)/kyogre_board_bg_tiles.4bpp \
-	$(RUBY)/ruby_board_strip.4bpp \
-	$(RUBY)/ruby_board_bgtop_tiles.4bpp \
-	$(RUBY)/ruby_board_bgbottom_tiles.4bpp \
-	$(RUBY)/ruby_board_bgramp_tiles.4bpp \
-	$(SAPPHIRE)/sapphire_board_strip.4bpp \
-	$(SAPPHIRE)/sapphire_board_bgtop_tiles.4bpp \
-	$(SAPPHIRE)/sapphire_board_bgbottom_tiles.4bpp \
-	$(SAPPHIRE)/sapphire_board_bgramp_tiles.4bpp \
-	$(SAPPHIRE)/sapphire_board_bg_tiles.4bpp \
-	$(RAYQUAZA)/rayquaza_board_bg_tiles.4bpp \
-	$(SPHEAL)/spheal_board_bg_tiles.4bpp
-
-.SECONDARY: $(DETILEMAP_SHEETS) $(addsuffix .lz,$(DETILEMAP_SHEETS))
diff --git a/tools/scripts/detilemap.py b/tools/scripts/detilemap.py
deleted file mode 100755
index 9455219d..00000000
--- a/tools/scripts/detilemap.py
+++ /dev/null
@@ -1,353 +0,0 @@
-#!/usr/bin/env python3
-"""detilemap -- convert between GBA BG tile sheets and assembled screen images.
-
-A BG tile sheet is stored deduplicated: the tilemap references each unique 8x8
-tile once, so the raw sheet is unreadable as a picture no matter what width it
-is exported at. This tool moves the editable form to the *assembled screen*,
-where the art is actually visible, and derives the sheet from it.
-
-    assemble   tiles.4bpp + tilemap.bin + palette.pal  ->  screen.png
-    extract    screen.png + tilemap.bin                ->  tiles.4bpp
-
-The screen image is an 8bpp indexed PNG carrying the full 256-colour GBA
-palette, with each pixel storing  bank * 16 + colour_index.  That keeps every
-per-cell palette bank distinct and makes the conversion lossless in both
-directions -- a 4bpp image could only hold one of the banks a screen uses.
-
-Flips are applied on assemble and undone on extract, so a cell that the tilemap
-marks h/v flipped still contributes its unflipped pixels back to the sheet.
-
-Ruby and Sapphire stream their board through a scroll ring, so a tilemap row R
-draws chunk R of a virtual strip rather than indexing the sheet directly. Pass
-`--row-chunk N` for those: the tile index becomes `R*N + (id % N)`. See
-data/board_data/VRAM_LAYOUT.md.
-
-Only stdlib is used, so this adds no build dependency.
-
-Examples
---------
-    detilemap.py assemble -t tiles.4bpp -m bg3.bin -p scene.pal -s 32x32 \\
-                          -o screen_bg3.png
-
-    detilemap.py extract  -n 704 -o tiles.4bpp \\
-                          --from screen_bg3.png:bg3.bin \\
-                          --from screen_bg1.png:bg1.bin
-
-`extract` takes as many screen/tilemap pairs as the sheet needs: one sheet is
-often shared by several BG layers. Tiles that no supplied tilemap references
-are emitted as zeroes and reported, so you can see exactly how much of the
-sheet was reconstructed rather than assumed.
-"""
-import argparse
-import struct
-import sys
-import zlib
-
-SCREEN_SIZES = {"32x32": (32, 32), "64x32": (64, 32), "32x64": (32, 64), "64x64": (64, 64)}
-
-
-# ---------------------------------------------------------------- PNG (8bpp indexed)
-
-def png_write(path, width, height, pixels, palette):
-    """pixels: bytes, one byte per pixel. palette: list of (r,g,b), <=256 entries."""
-    def chunk(tag, data):
-        return (struct.pack(">I", len(data)) + tag + data
-                + struct.pack(">I", zlib.crc32(tag + data) & 0xFFFFFFFF))
-
-    raw = bytearray()
-    for y in range(height):
-        raw.append(0)  # filter type 0 (None)
-        raw += pixels[y * width:(y + 1) * width]
-    plte = b"".join(bytes(c) for c in palette)
-    out = (b"\x89PNG\r\n\x1a\n"
-           + chunk(b"IHDR", struct.pack(">IIBBBBB", width, height, 8, 3, 0, 0, 0))
-           + chunk(b"PLTE", plte)
-           + chunk(b"IDAT", zlib.compress(bytes(raw), 9))
-           + chunk(b"IEND", b""))
-    with open(path, "wb") as fp:
-        fp.write(out)
-
-
-def png_read(path):
-    """Returns (width, height, pixels bytes one-per-pixel, palette list)."""
-    data = open(path, "rb").read()
-    if data[:8] != b"\x89PNG\r\n\x1a\n":
-        raise SystemExit(f"{path}: not a PNG")
-    pos, idat, plte, ihdr = 8, bytearray(), None, None
-    while pos < len(data):
-        ln, tag = struct.unpack(">I4s", data[pos:pos + 8])
-        body = data[pos + 8:pos + 8 + ln]
-        if tag == b"IHDR":
-            ihdr = struct.unpack(">IIBBBBB", body)
-        elif tag == b"PLTE":
-            plte = body
-        elif tag == b"IDAT":
-            idat += body
-        pos += 12 + ln
-    w, h, bd, ct, comp, filt, inter = ihdr
-    if ct != 3 or bd not in (1, 2, 4, 8):
-        raise SystemExit(f"{path}: need an indexed PNG (colour type 3), got type {ct} depth {bd}")
-    if inter:
-        raise SystemExit(f"{path}: interlaced PNGs are not supported")
-
-    raw = zlib.decompress(bytes(idat))
-    bpp = 1  # bytes per pixel for filtering purposes at bd<=8
-    stride = (w * bd + 7) // 8
-    rows, prev, pos = [], bytearray(stride), 0
-    for _ in range(h):
-        ftype = raw[pos]; pos += 1
-        line = bytearray(raw[pos:pos + stride]); pos += stride
-        for i in range(stride):
-            a = line[i - bpp] if i >= bpp else 0
-            b = prev[i]
-            c = prev[i - bpp] if i >= bpp else 0
-            if ftype == 1:   line[i] = (line[i] + a) & 0xFF
-            elif ftype == 2: line[i] = (line[i] + b) & 0xFF
-            elif ftype == 3: line[i] = (line[i] + ((a + b) >> 1)) & 0xFF
-            elif ftype == 4:
-                p = a + b - c
-                pa, pb, pc = abs(p - a), abs(p - b), abs(p - c)
-                pr = a if (pa <= pb and pa <= pc) else (b if pb <= pc else c)
-                line[i] = (line[i] + pr) & 0xFF
-            elif ftype != 0:
-                raise SystemExit(f"{path}: bad PNG filter type {ftype}")
-        rows.append(bytes(line)); prev = line
-
-    if bd == 8:
-        pixels = b"".join(rows)
-    else:  # unpack sub-byte indices
-        px = bytearray()
-        mask = (1 << bd) - 1
-        for line in rows:
-            for x in range(w):
-                byte = line[(x * bd) // 8]
-                shift = 8 - bd - ((x * bd) % 8)
-                px.append((byte >> shift) & mask)
-        pixels = bytes(px)
-    pal = [tuple(plte[i:i + 3]) for i in range(0, len(plte or b""), 3)]
-    return w, h, pixels, pal
-
-
-# ---------------------------------------------------------------- GBA data
-
-def read_jasc(path):
-    lines = open(path, "rb").read().decode().replace("\r\n", "\n").split("\n")
-    if lines[0] != "JASC-PAL":
-        raise SystemExit(f"{path}: not a JASC palette")
-    n = int(lines[2])
-    return [tuple(map(int, lines[3 + k].split())) for k in range(n)]
-
-
-def split_map_arg(arg):
-    """`file.bin` or `file.bin@N` -- N is an entry offset, for files holding
-    several screens back to back."""
-    if "@" in arg:
-        path, off = arg.rsplit("@", 1)
-        return path, int(off, 0)
-    return arg, 0
-
-
-def read_tilemap(path, cols, rows, offset=0):
-    """GBA stores >32-wide/tall screens as 32x32 screenblocks in TL,TR,BL,BR order."""
-    blob = open(path, "rb").read()
-    entries = [int.from_bytes(blob[i:i + 2], "little") for i in range(0, len(blob), 2)]
-    entries = entries[offset:]
-    need = cols * rows
-    if len(entries) < need:
-        raise SystemExit(f"{path}: {len(entries)} entries from offset {offset}, "
-                         f"need {need} for {cols}x{rows}")
-    cell = {}
-    blocks_x = cols // 32
-    for i, e in enumerate(entries[:need]):
-        blk, off = divmod(i, 1024)
-        r = off // 32 + 32 * (blk // blocks_x)
-        c = off % 32 + 32 * (blk % blocks_x)
-        cell[(r, c)] = (e & 0x3FF, (e >> 10) & 1, (e >> 11) & 1, e >> 12)
-    return cell
-
-
-def tile_pixels(sheet, tile):
-    """Return 64 palette indices for one 4bpp tile, row-major."""
-    out = bytearray(64)
-    base = tile * 32
-    for y in range(8):
-        for x in range(0, 8, 2):
-            byte = sheet[base + y * 4 + x // 2]
-            out[y * 8 + x] = byte & 0xF
-            out[y * 8 + x + 1] = byte >> 4
-    return out
-
-
-# ---------------------------------------------------------------- commands
-
-def cmd_assemble(a):
-    cols, rows = SCREEN_SIZES[a.size]
-    sheet = open(a.tiles, "rb").read()
-    ntiles = len(sheet) // 32
-    pal = read_jasc(a.palette)
-    if len(pal) < 256:
-        pal = pal + [(0, 0, 0)] * (256 - len(pal))
-    map_path, map_off = split_map_arg(a.map)
-    cells = read_tilemap(map_path, cols, rows, map_off)
-
-    w, h = cols * 8, rows * 8
-    px = bytearray(w * h)
-    missing = set()
-    for (r, c), (tile, hf, vf, bank) in cells.items():
-        if a.row_chunk:
-            tile = r * a.row_chunk + (tile % a.row_chunk)
-        if tile >= ntiles:
-            missing.add(tile)
-            continue
-        tp = tile_pixels(sheet, tile)
-        for y in range(8):
-            for x in range(8):
-                sx = 7 - x if hf else x
-                sy = 7 - y if vf else y
-                px[(r * 8 + y) * w + c * 8 + x] = bank * 16 + tp[sy * 8 + sx]
-    png_write(a.output, w, h, bytes(px), pal[:256])
-    print(f"assembled {a.output}  {w}x{h}  ({cols}x{rows} cells, {ntiles} tiles in sheet)")
-    if missing:
-        lo, hi = min(missing), max(missing)
-        print(f"  note: {len(missing)} tile ids referenced but outside this sheet ({lo}..{hi}) "
-              f"-- those cells are left blank")
-
-
-def cmd_extract(a):
-    sheet = bytearray(a.count * 32)
-    written = {}
-    conflicts = []
-
-    for spec in getattr(a, "from"):
-        parts = spec.split(":")
-        if len(parts) == 3 and parts[2] in SCREEN_SIZES:
-            png_path, map_path, size = parts
-        elif len(parts) == 2:
-            png_path, map_path, size = parts[0], parts[1], a.size
-        else:
-            raise SystemExit(f"--from needs PNG:TILEMAP[:SIZE], got {spec!r}")
-        cols, rows = SCREEN_SIZES[size]
-        w, h, px, _ = png_read(png_path)
-        if (w, h) != (cols * 8, rows * 8):
-            raise SystemExit(f"{png_path}: is {w}x{h}, expected {cols*8}x{rows*8} for size {size}")
-        map_file, map_off = split_map_arg(map_path)
-        cells = read_tilemap(map_file, cols, rows, map_off)
-
-        for (r, c), (tile, hf, vf, bank) in cells.items():
-            if a.row_chunk:
-                tile = r * a.row_chunk + (tile % a.row_chunk)
-            if tile >= a.count:
-                continue
-            tp = bytearray(64)
-            ok = True
-            for y in range(8):
-                for x in range(8):
-                    v = px[(r * 8 + y) * w + c * 8 + x]
-                    if v >> 4 != bank:
-                        ok = False
-                    sx = 7 - x if hf else x
-                    sy = 7 - y if vf else y
-                    tp[sy * 8 + sx] = v & 0xF
-                if not ok:
-                    break
-            if not ok:
-                conflicts.append(("bank", png_path, r, c, tile, bank))
-                continue
-            packed = bytes((tp[i * 8 + j] | (tp[i * 8 + j + 1] << 4))
-                           for i in range(8) for j in range(0, 8, 2))
-            if tile in written and written[tile] != packed:
-                conflicts.append(("pixels", png_path, r, c, tile, bank))
-                continue
-            written[tile] = packed
-
-    # Tiles that live in the sheet but that no tilemap references. They cannot
-    # come from a screen, so they are supplied as a plain linear tile strip.
-    for spec in getattr(a, "extra", None) or []:
-        png_path, first = split_map_arg(spec)
-        if "@" not in spec:
-            raise SystemExit(f"--extra needs PNG@FIRST_TILE, got {spec!r}")
-        w, h, px, _ = png_read(png_path)
-        if w % 8 or h % 8:
-            raise SystemExit(f"{png_path}: is {w}x{h}, must be a whole number of 8x8 tiles")
-        per_row = w // 8
-        for n in range((w // 8) * (h // 8)):
-            tile = first + n
-            if tile >= a.count:
-                raise SystemExit(f"{png_path}: tile {tile} is past the end of a {a.count}-tile sheet")
-            tr, tc = divmod(n, per_row)
-            packed = bytes(
-                ((px[(tr * 8 + y) * w + tc * 8 + x] & 0xF)
-                 | ((px[(tr * 8 + y) * w + tc * 8 + x + 1] & 0xF) << 4))
-                for y in range(8) for x in range(0, 8, 2))
-            if tile in written and written[tile] != packed:
-                conflicts.append(("pixels", png_path, 0, n, tile, 0))
-                continue
-            written[tile] = packed
-
-    for tile, packed in written.items():
-        sheet[tile * 32:(tile + 1) * 32] = packed
-
-    if conflicts:
-        print(f"error: {len(conflicts)} cell(s) did not agree with the tilemap:", file=sys.stderr)
-        for kind, p, r, c, tile, bank in conflicts[:10]:
-            if kind == "bank":
-                print(f"  {p} cell ({r},{c}): pixels are not in palette bank {bank}", file=sys.stderr)
-            else:
-                print(f"  {p} cell ({r},{c}): tile {tile} drawn two different ways", file=sys.stderr)
-        if len(conflicts) > 10:
-            print(f"  ... and {len(conflicts) - 10} more", file=sys.stderr)
-        return 1
-
-    with open(a.output, "wb") as fp:
-        fp.write(sheet)
-    blank = a.count - len(written)
-    print(f"extracted {a.output}  {a.count} tiles, {len(written)} reconstructed from screens")
-    if blank:
-        ids = sorted(set(range(a.count)) - set(written))
-        runs, start = [], ids[0]
-        for i in range(1, len(ids) + 1):
-            if i == len(ids) or ids[i] != ids[i - 1] + 1:
-                runs.append((start, ids[i - 1])); start = ids[i] if i < len(ids) else 0
-        pretty = ", ".join(f"{x}" if x == y else f"{x}-{y}" for x, y in runs[:6])
-        print(f"  note: {blank} tile(s) unreferenced, emitted as zeroes ({pretty}"
-              f"{', ...' if len(runs) > 6 else ''})")
-    return 0
-
-
-def main():
-    ap = argparse.ArgumentParser(description=__doc__.split("\n")[0],
-                                 formatter_class=argparse.RawDescriptionHelpFormatter)
-    sub = ap.add_subparsers(dest="cmd", required=True)
-
-    asm = sub.add_parser("assemble", help="tiles + tilemap + palette -> screen PNG")
-    asm.add_argument("-t", "--tiles", required=True)
-    asm.add_argument("-m", "--map", required=True)
-    asm.add_argument("-p", "--palette", required=True)
-    asm.add_argument("-s", "--size", default="32x32", choices=sorted(SCREEN_SIZES))
-    asm.add_argument("-o", "--output", required=True)
-    asm.add_argument("--row-chunk", type=int, default=0, metavar="N",
-                     help="scroll-ring addressing: tile index is R*N + (id %% N)")
-    asm.set_defaults(fn=cmd_assemble)
-
-    ext = sub.add_parser("extract", help="screen PNG(s) + tilemap(s) -> tiles")
-    ext.add_argument("--from", action="append", required=True, metavar="PNG:TILEMAP[:SIZE]",
-                     help="screen image and the tilemap that placed it, with an optional "
-                          "per-pair screen size; repeatable. The tilemap may carry an "
-                          "@ENTRY_OFFSET suffix when one file holds several screens.")
-    ext.add_argument("--extra", action="append", metavar="PNG@FIRST_TILE",
-                     help="linear tile strip for sheet tiles no tilemap references; "
-                          "written into consecutive slots from FIRST_TILE. Repeatable.")
-    ext.add_argument("-n", "--count", type=int, required=True, help="tiles in the output sheet")
-    ext.add_argument("-s", "--size", default="32x32", choices=sorted(SCREEN_SIZES),
-                     help="default screen size for --from pairs that do not give one")
-    ext.add_argument("-o", "--output", required=True)
-    ext.add_argument("--row-chunk", type=int, default=0, metavar="N",
-                     help="scroll-ring addressing: tile index is R*N + (id %% N)")
-    ext.set_defaults(fn=cmd_extract)
-
-    a = ap.parse_args()
-    return a.fn(a) or 0
-
-
-if __name__ == "__main__":
-    sys.exit(main())