diff --git a/index.html b/index.html
index f0051381..7fc92bde 100644
--- a/index.html
+++ b/index.html
@@ -203,7 +203,6 @@ body {
             <li><a class="dropdown-item" href="?platform=atari8-5200.mame">Atari 5200 (MAME)</a></li>
             <hr>
             <li><a class="dropdown-item" href="?platform=vcs.stellerator">Atari 2600 (Stellerator)</a></li>
-            <li><a class="dropdown-item" href="?platform=vcs.mame">Atari 2600 (MAME)</a></li>
             <li><a class="dropdown-item" href="?platform=coleco.mame">ColecoVision (MAME)</a></li>
             <li><a class="dropdown-item" href="?platform=nes.mame">NES (MAME)</a></li>
             <hr>
diff --git a/presets/apple2/siegegame.c b/presets/apple2/siegegame.c
index ab5d4bdc..17788a52 100644
--- a/presets/apple2/siegegame.c
+++ b/presets/apple2/siegegame.c
@@ -82,6 +82,7 @@ void draw_playfield() {
   cputsxy(20, 0, "Plyr2:");
   cputcxy( 7, 0, players[0].score+'0');
   cputcxy(27, 0, players[1].score+'0');
+  cputsxy( 6, ROWS-1, "I/J/K/L - UP/LEFT/DOWN/RIGHT");
 }
 
 typedef enum { D_RIGHT, D_DOWN, D_LEFT, D_UP } dir_t;
@@ -129,8 +130,8 @@ void human_control(Player* p) {
   switch (key) {
     case 'I': dir = D_UP; break;
     case 'J': dir = D_LEFT; break;
-    case 'K': dir = D_RIGHT; break;
-    case 'M': dir = D_DOWN; break;
+    case 'L': dir = D_RIGHT; break;
+    case 'K': dir = D_DOWN; break;
   }
   // don't let the player reverse direction
   if (dir < 0x80 && dir != (p->dir ^ 2)) {
diff --git a/src/docs/asset-headers.md b/src/docs/asset-headers.md
index ca40e487..430ba30c 100644
--- a/src/docs/asset-headers.md
+++ b/src/docs/asset-headers.md
@@ -9,10 +9,10 @@ a comment, sitting right above the bytes:
 const byte tiles[] = { ... };
 ```
 
-From that short comment the editor knows the data is two 8×8, 1-bit
-images, most significant bit on the left. You write the header by hand
-once, and from then on the Asset Editor can draw and edit the data for
-you.
+The Asset Editor scans that comment and reads the JSON inside.
+It then knows how to convert the bytes inside the array to and from an image.
+
+For example, the above comment represents two images, 8x8 pixels, 1 bit per pixel, most significant bit on the left.
 
 ## Header syntax
 
@@ -26,14 +26,14 @@ which depends on the language:
 | Assembly | `;;{w:8,h:8};;` | next `;;` |
 | Verilog | `/*{w:8,h:8}*/` | next `end` |
 
-**Each number needs a radix prefix so the editor can read it.** It
-recognizes `0xNN`, `$NN`, `#$NN`, `%0101`, `0b0101`, `8'hNN`, `8'b0101`,
-and assembler `hex 1f20…` statements. It also remembers the notation you
-used and writes edits back the same way, so a file of `$`-prefixed bytes
-stays `$`-prefixed. The one thing it will *not* read is **plain
-decimal** — a block of `{24,60,126,…}` parses as zero values and reports
-*"Expected 8 value(s), found 0"*.
+**Each number needs a radix prefix.**
+It recognizes `0xNN`, `$NN`, `#$NN`, `%0101`, `0b0101`, `8'hNN`, `8'b0101`,
+and assembler `hex aabbcc…` statements.
+It remembers the notation you used and writes each number back the same way.
+It does *not* recognize **plain decimal** numbers
+— a block of `{24,60,126,…}` parses as zero values and reports an error.
 
+Examples:
 ```c
 /*{w:8,h:8,bpp:1,count:2,brev:1}*/
 const byte tiles[] = {
@@ -45,15 +45,14 @@ const byte tiles[] = {
 ```asm
 ;;{w:8,h:8,count:1,brev:1,flip:1};;
 PlayerGfx:
-        .byte $18,$3c,$7e,$ff,$ff,$7e,$3c,$18
+       .byte $18,$3c,$7e,$ff
+       hex ff7e3c18
 ;;
 ```
 
-### Writing JSON loosely
-
-You don't have to quote the keys. The scanner rewrites `([A-Za-z]+):` to
-`"$1":` before parsing, so `w:8` and `"w":8` mean the same thing. String
-*values* still need their quotes, though: `pal:"nes"`, `comp:"rletag"`.
+The JSON parser isn't strict, so you don't have to "quote" keys --
+`w:8` and `"w":8` mean the same thing.
+String *values* still need their quotes, though: `pal:"nes"`, `comp:"rletag"`.
 
 ### Things to watch out for
 
@@ -76,11 +75,6 @@ const char sprite[] = {
 };
 ```
 
-The path is resolved first exactly as written, then relative to the
-directory of the file containing the header (`sub/main.c` + `data.bin` →
-`sub/data.bin`). The file's byte length is validated against the format
-the same way inline data is.
-
 ### Overlapping arrays
 
 The scanner decides where a data block ends from how the header starts,
@@ -110,10 +104,10 @@ everything else falls back to a sensible default.
 | `h` | *required* | Height in pixels |
 | `count` | `1` | Number of images |
 | `bpp` | `1` | Bits per pixel |
-| `np` | `1` | Number of bitplanes (colors = 2<sup>bpp&times;np</sup>) |
+| `np` | `1` | Number of bitplanes (colors = 2<sup>bpp&dot;np</sup>) |
 | `bpw` | `8` | Bits per word (8, 16, 32) |
 | `sl` | `ceil(w*bpp/bpw)` | Words per scanline (stride) |
-| `wpimg` | `sl*h` | Words per image — use when hardware pads images |
+| `wpimg` | `sl*h` | Words per image (for padding) |
 | `pofs` | `sl*h*count` | Distance between bitplanes, in words |
 | `skip` | `0` | Words to skip at the start of the whole block |
 | `brev` | `false` | MSB is the leftmost pixel |
@@ -149,10 +143,9 @@ A block with `pal` and no `w`/`h` describes a palette instead of an image.
   block holds.
 - **A name**: `"nes"`, `"vcs"`, `"c64"`, `"gb"`, `"ap2lores"`,
   `"astrocade"`, or `"pacman"`.
-  These are the only recognized names — an
-  unknown one reports `No palette named X`.
+  An unknown name reports an error.
 
-Bitmaps pick up their colors from palette blocks **anywhere in the open
+Bitmaps pick up their colors from palette blocks **anywhere in the current
 project**, matched by entry count — a 4-color bitmap offers every 4-entry
 palette (and every 4-entry slice named by a `layout`) in a dropdown.
 Projects fall back to a default palette when no palette block matches.
diff --git a/src/docs/asseteditor.md b/src/docs/asseteditor.md
index 9a171dce..33f33a42 100644
--- a/src/docs/asseteditor.md
+++ b/src/docs/asseteditor.md
@@ -1,6 +1,6 @@
 # Asset Editor
 
-The Asset Editor finds [Asset Headers](asset-headers.md) in your source — small JSON
+The Asset Editor finds [asset headers](asset-headers.md) in your source — small JSON
 descriptors inside comments — and turns the data block that follows into
 an editable bitmap, tilemap, or palette. Edits are written straight back
 into the source text, preserving the original number base and formatting
diff --git a/src/platform/atari8.ts b/src/platform/atari8.ts
index 67274013..58b5a7e8 100644
--- a/src/platform/atari8.ts
+++ b/src/platform/atari8.ts
@@ -161,7 +161,6 @@ function atari8_showHelp() {
 ///
 
 PLATFORMS['atari8-800.xlmame'] = Atari800MAMEPlatform
-PLATFORMS['atari8-800xl.mame'] = Atari800MAMEPlatform // for dithertron
 PLATFORMS['atari8-5200.mame'] = Atari5200MAMEPlatform
 PLATFORMS['atari8-800'] = Atari800Platform
 PLATFORMS['atari8-5200'] = Atari5200Platform
diff --git a/src/tools/buildpresets.ts b/src/tools/buildpresets.ts
index 23fef0d6..3c852452 100644
--- a/src/tools/buildpresets.ts
+++ b/src/tools/buildpresets.ts
@@ -62,7 +62,6 @@ const DEFAULT_TIMEOUT = 120000;
 
 // skip these platforms, they aren't ready yet or otherwise broken
 const SKIP_PLATFORMS = [
-    'atari8-800xl.mame',
     'vector-ataribw',
     'williams-defender',
     'astrocade-arcade',