diff --git a/challenges/medium/81_int4_matmul/challenge.html b/challenges/medium/81_int4_matmul/challenge.html
index 1cd5e43..6df9ade 100644
--- a/challenges/medium/81_int4_matmul/challenge.html
+++ b/challenges/medium/81_int4_matmul/challenge.html
@@ -6,132 +6,6 @@
   <code>W</code> is the dequantized float16 weight matrix of shape <code>N &times; K</code>.
 </p>
 
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-      <path d="M0,0 L0,6 L8,3 z" fill="#aaa"/>
-    </marker>
-  </defs>
-
-  <!-- ============================================================ -->
-  <!-- ROW 1: UNPACK  —  packed byte → two unsigned nibbles → signed -->
-  <!-- ============================================================ -->
-  <text x="18" y="20" fill="#666" font-size="10">STEP 1: UNPACK</text>
-
-  <!-- Packed byte -->
-  <text x="80" y="48" fill="#ccc" font-size="11" text-anchor="middle">w_q[n, i]</text>
-  <rect x="20" y="56" width="120" height="32" fill="#1a3a5c" rx="4" stroke="#4a9edd" stroke-width="1.5"/>
-  <line x1="80" y1="56" x2="80" y2="88" stroke="#4a9edd" stroke-width="1" stroke-dasharray="3,2"/>
-  <text x="50" y="77" fill="#4a9edd" font-size="10" text-anchor="middle">hi 7:4</text>
-  <text x="110" y="77" fill="#7ec87e" font-size="10" text-anchor="middle">lo 3:0</text>
-
-  <!-- Arrow right -->
-  <text x="160" y="77" fill="#aaa" font-size="14" text-anchor="middle">&#x2192;</text>
-
-  <!-- Unsigned nibbles -->
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-  <text x="205" y="77" fill="#4a9edd" font-size="10" text-anchor="middle">9</text>
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-  <text x="261" y="77" fill="#7ec87e" font-size="10" text-anchor="middle">10</text>
-
-  <!-- "- 8" arrow -->
-  <text x="310" y="77" fill="#ccc" font-size="11" text-anchor="middle">&#x2212; 8</text>
-  <text x="345" y="77" fill="#aaa" font-size="14" text-anchor="middle">&#x2192;</text>
-
-  <!-- Signed int4 -->
-  <rect x="365" y="56" width="50" height="32" fill="#3a2a1a" rx="4" stroke="#e0a040" stroke-width="1.5"/>
-  <text x="390" y="77" fill="#e0a040" font-size="10" text-anchor="middle">+1</text>
-  <rect x="421" y="56" width="50" height="32" fill="#3a2a1a" rx="4" stroke="#e0a040" stroke-width="1.5"/>
-  <text x="446" y="77" fill="#e0a040" font-size="10" text-anchor="middle">+2</text>
-
-  <text x="540" y="77" fill="#888" font-size="10" text-anchor="middle">signed int4 [&#x2212;8, 7]</text>
-
-  <!-- ============================================================ -->
-  <!-- ROW 2: GROUP-WISE SCALING  —  show K=8, group_size=4         -->
-  <!-- ============================================================ -->
-  <text x="18" y="112" fill="#666" font-size="10">STEP 2: DEQUANTIZE (example: one row n, K=8, group_size=4)</text>
-
-  <!-- K-axis label -->
-  <text x="350" y="136" fill="#888" font-size="10" text-anchor="middle">k &#x2192;</text>
-
-  <!-- Group 0 bracket + cells -->
-  <text x="145" y="136" fill="#c060e0" font-size="9" text-anchor="middle">group 0: scale[n, 0]</text>
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-  <text x="81" y="161" fill="#e0a040" font-size="10" text-anchor="middle">+1</text>
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-  <text x="131" y="161" fill="#e0a040" font-size="10" text-anchor="middle">+2</text>
-  <rect x="158" y="142" width="46" height="28" fill="#3a2a1a" rx="3" stroke="#e0a040" stroke-width="1"/>
-  <text x="181" y="161" fill="#e0a040" font-size="10" text-anchor="middle">&#x2212;1</text>
-  <rect x="208" y="142" width="46" height="28" fill="#3a2a1a" rx="3" stroke="#e0a040" stroke-width="1"/>
-  <text x="231" y="161" fill="#e0a040" font-size="10" text-anchor="middle">+3</text>
-  <!-- Group 0 bracket -->
-  <rect x="56" y="140" width="200" height="32" rx="4" fill="none" stroke="#c060e0" stroke-width="1.5" stroke-dasharray="4,2"/>
-
-  <!-- Group 1 bracket + cells -->
-  <text x="385" y="136" fill="#c060e0" font-size="9" text-anchor="middle">group 1: scale[n, 1]</text>
-  <rect x="298" y="142" width="46" height="28" fill="#3a2a1a" rx="3" stroke="#e0a040" stroke-width="1"/>
-  <text x="321" y="161" fill="#e0a040" font-size="10" text-anchor="middle">0</text>
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-  <text x="371" y="161" fill="#e0a040" font-size="10" text-anchor="middle">&#x2212;3</text>
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-
-  <!-- "int4" label on left -->
-  <text x="30" y="161" fill="#e0a040" font-size="9">int4</text>
-
-  <!-- Multiply arrows down -->
-  <text x="156" y="190" fill="#ccc" font-size="12" text-anchor="middle">&#xd7; scale[n, 0]</text>
-  <text x="396" y="190" fill="#ccc" font-size="12" text-anchor="middle">&#xd7; scale[n, 1]</text>
-  <line x1="156" y1="172" x2="156" y2="198" stroke="#aaa" stroke-width="1" stroke-dasharray="3,2"/>
-  <line x1="396" y1="172" x2="396" y2="198" stroke="#aaa" stroke-width="1" stroke-dasharray="3,2"/>
-
-  <!-- Dequantized row -->
-  <text x="30" y="217" fill="#40c080" font-size="9">fp16</text>
-  <rect x="56" y="202" width="200" height="28" fill="#1a3a2a" rx="4" stroke="#40c080" stroke-width="1.5"/>
-  <text x="156" y="221" fill="#40c080" font-size="10" text-anchor="middle">W[n, 0..3] float16</text>
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-  <text x="396" y="221" fill="#40c080" font-size="10" text-anchor="middle">W[n, 4..7] float16</text>
-
-  <!-- Formula -->
-  <text x="275" y="252" fill="#ccc" font-size="10" text-anchor="middle">W[n, k] = (nibble &#x2212; 8) &#xd7; scales[n, k // group_size]</text>
-
-  <!-- ============================================================ -->
-  <!-- ROW 3: MATMUL                                                -->
-  <!-- ============================================================ -->
-  <text x="18" y="280" fill="#666" font-size="10">STEP 3: MATMUL</text>
-
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-  <text x="100" y="322" fill="#4a9edd" font-size="10" text-anchor="middle">x [M&#xd7;K]</text>
-  <text x="100" y="340" fill="#4a9edd" font-size="9" text-anchor="middle">float16</text>
-
-  <!-- multiply sign -->
-  <text x="162" y="330" fill="#ccc" font-size="16" text-anchor="middle">&#xd7;</text>
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-  <!-- W^T box -->
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-  <text x="235" y="322" fill="#40c080" font-size="10" text-anchor="middle">W&#x1d40; [K&#xd7;N]</text>
-  <text x="235" y="340" fill="#40c080" font-size="9" text-anchor="middle">float16</text>
-
-  <!-- equals sign -->
-  <text x="310" y="330" fill="#ccc" font-size="16" text-anchor="middle">=</text>
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-  <!-- y output box -->
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-  <text x="380" y="322" fill="#e05050" font-size="10" text-anchor="middle">y [M&#xd7;N]</text>
-  <text x="380" y="340" fill="#e05050" font-size="9" text-anchor="middle">float16</text>
-
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-  <text x="260" y="270" fill="#40c080" font-size="9">dequantized</text>
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-
 <p>
   <strong>Packing format:</strong> Each byte of <code>w_q</code> stores two INT4 weights. The
   high nibble (bits 7&ndash;4) holds weight <code>w[n, 2i]</code> and the low nibble (bits