diff --git a/notes/pics/reverse-k-group.png b/notes/pics/reverse-k-group.png
index 42eef477..7041a694 100644
Binary files a/notes/pics/reverse-k-group.png and b/notes/pics/reverse-k-group.png differ
diff --git a/tools/diagram/src/reverse-k-group.svg b/tools/diagram/src/reverse-k-group.svg
index 09f1d1f6..d74766e3 100644
--- a/tools/diagram/src/reverse-k-group.svg
+++ b/tools/diagram/src/reverse-k-group.svg
@@ -1,59 +1,53 @@
 <svg xmlns="http://www.w3.org/2000/svg" width="600" height="300" viewBox="0 0 600 300">
   <style>
-    text { font-family: "PingFang SC", "Microsoft YaHei", Helvetica, Arial, sans-serif; fill: #666; font-size: 12px; }
-    .title { font-weight: bold; font-size: 15px; fill: #777; text-anchor: middle; }
+    text { font-family: "PingFang SC", "Microsoft YaHei", Helvetica, Arial, sans-serif; fill: #3F3F3F; font-size: 12px; }
+    .title { font-weight: bold; font-size: 15px; fill: #333; text-anchor: middle; }
     .b { font-weight: bold; }
     .c { text-anchor: middle; }
     .e { text-anchor: end; }
     .note { fill: #C0605A; }
     .ok { fill: #6A9F68; }
-    .sub { font-size: 11px; fill: #888; }
+    .sub { font-size: 11px; fill: #6E6E6E; }
     .mono { font-family: Menlo, Consolas, monospace; }
-    .arrow { stroke: #666; stroke-width: 1.3; fill: none; marker-end: url(#a); }
+    .arrow { stroke: #555; stroke-width: 1.1; fill: none; marker-end: url(#a); }
     .red { stroke: #C0605A; marker-end: url(#r); }
     .green { stroke: #6A9F68; marker-end: url(#g); }
     .dash { stroke-dasharray: 5 4; }
-    .line { stroke: #666; stroke-width: 1.3; fill: none; }
+    .line { stroke: #555; stroke-width: 1.1; fill: none; }
     .frame { fill: none; stroke: #999; stroke-width: 1; stroke-dasharray: 4 3; }
     .shadow { fill: #DADADA; }
   </style>
   <defs>
     <marker id="a" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
-      <path d="M1,1 L9,5 L1,9" fill="none" stroke="#666" stroke-width="1.6"/>
+      <path d="M1,1.5 L9.5,5 L1,8.5 z" fill="#555"/>
     </marker>
     <marker id="r" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
-      <path d="M1,1 L9,5 L1,9" fill="none" stroke="#C0605A" stroke-width="1.6"/>
+      <path d="M1,1.5 L9.5,5 L1,8.5 z" fill="#C0605A"/>
     </marker>
     <marker id="g" viewBox="0 0 10 10" refX="9" refY="5" markerWidth="7" markerHeight="7" orient="auto-start-reverse">
-      <path d="M1,1 L9,5 L1,9" fill="none" stroke="#6A9F68" stroke-width="1.6"/>
+      <path d="M1,1.5 L9.5,5 L1,8.5 z" fill="#6A9F68"/>
     </marker>
   </defs>
   <rect width="100%" height="100%" fill="#FFFFFF"/>
 
   <text x="300" y="28" class="title">K 个一组翻转链表（k = 2）</text>
   <text x="20" y="90" class="b">翻转前</text>
-  <rect x="87" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="85" y="69" width="50" height="32" rx="6" fill="#E6E6E6"/>
+  <rect x="85" y="69" width="50" height="32" rx="6" fill="#EAE9E7" stroke="#BFBEBA"/>
   <text x="110" y="89.5" class="c b">dummy</text>
   <line x1="137" y1="85" x2="163" y2="85" class="arrow "/>
-  <rect x="167" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="165" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="165" y="69" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="190" y="89.5" class="c b">1</text>
   <line x1="217" y1="85" x2="243" y2="85" class="arrow "/>
-  <rect x="247" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="245" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="245" y="69" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="270" y="89.5" class="c b">2</text>
   <line x1="297" y1="85" x2="323" y2="85" class="arrow "/>
-  <rect x="327" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="325" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="325" y="69" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="350" y="89.5" class="c b">3</text>
   <line x1="377" y1="85" x2="403" y2="85" class="arrow "/>
-  <rect x="407" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="405" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="405" y="69" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="430" y="89.5" class="c b">4</text>
   <line x1="457" y1="85" x2="483" y2="85" class="arrow "/>
-  <rect x="487" y="71" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="485" y="69" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="485" y="69" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="510" y="89.5" class="c b">5</text>
   <line x1="110" y1="131" x2="110" y2="105" class="arrow "/>
   <text x="110" y="147" class="c ">pre</text>
@@ -64,28 +58,22 @@
   <line x1="350" y1="131" x2="350" y2="105" class="arrow "/>
   <text x="350" y="147" class="c ">next</text>
   <text x="20" y="205" class="b">翻转后</text>
-  <rect x="87" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="85" y="184" width="50" height="32" rx="6" fill="#E6E6E6"/>
+  <rect x="85" y="184" width="50" height="32" rx="6" fill="#EAE9E7" stroke="#BFBEBA"/>
   <text x="110" y="204.5" class="c b">dummy</text>
   <line x1="137" y1="200" x2="163" y2="200" class="arrow "/>
-  <rect x="167" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="165" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="165" y="184" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="190" y="204.5" class="c b">2</text>
   <line x1="217" y1="200" x2="243" y2="200" class="arrow "/>
-  <rect x="247" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="245" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="245" y="184" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="270" y="204.5" class="c b">1</text>
   <line x1="297" y1="200" x2="323" y2="200" class="arrow "/>
-  <rect x="327" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="325" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="325" y="184" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="350" y="204.5" class="c b">3</text>
   <line x1="377" y1="200" x2="403" y2="200" class="arrow "/>
-  <rect x="407" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="405" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="405" y="184" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="430" y="204.5" class="c b">4</text>
   <line x1="457" y1="200" x2="483" y2="200" class="arrow "/>
-  <rect x="487" y="186" width="50" height="32" rx="6" class="shadow"/>
-  <rect x="485" y="184" width="50" height="32" rx="6" fill="#B1DDF0"/>
+  <rect x="485" y="184" width="50" height="32" rx="6" fill="#C6E4FB" stroke="#7FB2D6"/>
   <text x="510" y="204.5" class="c b">5</text>
   <line x1="110" y1="246" x2="110" y2="220" class="arrow "/>
   <text x="110" y="262" class="c ">pre.next = tail</text>