/* ================= theme tokens ================= */
:root{
  --green:#04AA6D; --green-dark:#03945f; --green-soft:#e7f6ef; --green-border:#cbe8db;
  --yellow:#ffd000;
  --bg:#ffffff; --text:#000000; --muted:#555555; --muted2:#777777;
  --surface:#ffffff; --surface-2:#f7f7f7; --sidebar:#f1f1f1; --sidebar-hover:#cccccc;
  --border:#dddddd; --border-soft:#f0f0f0;
  --code-bg:#f6f8fa; --code-fg:#c7254e; --pre-bg:#ffffff; --pre-fg:#000000;
  --link:#03945f;
  --note-bg:#fff4d4; --note-bd:#ffd000;
  --warn-bg:#ffe7e7; --warn-bd:#d9534f;
  --tip-bg:#e7f0ff;  --tip-bd:#2f6fd0;
  --ok-bg:#e2f7ea;   --no-bg:#ffe7e7;
  --topbar:#282a35; --topbar-fg:#ffffff;
  --kw:#0d6bc4; --str:#aa1111; --cmt:#6a9955;
  --mark:#ffe9a8; --shadow:rgba(0,0,0,.05);
  color-scheme:light;
}
/* dark เมื่อระบบตั้ง dark และผู้ใช้ไม่ได้บังคับ light */
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --green:#2ec98c; --green-dark:#25b47c; --green-soft:#12291f; --green-border:#1f4e3a;
    --yellow:#ffd94d;
    --bg:#14161c; --text:#e6e8ee; --muted:#a7adba; --muted2:#8b93a3;
    --surface:#1a1d25; --surface-2:#20242e; --sidebar:#1a1d25; --sidebar-hover:#2b303c;
    --border:#333a49; --border-soft:#262b36;
    --code-bg:#20242e; --code-fg:#ff9ec0; --pre-bg:#11141a; --pre-fg:#e6e8ee;
    --link:#4fd6a0;
    --note-bg:#2e2712; --note-bd:#c9a227;
    --warn-bg:#331b1b; --warn-bd:#e06c6c;
    --tip-bg:#16233a;  --tip-bd:#5a95e8;
    --ok-bg:#132a1f;   --no-bg:#331b1b;
    --topbar:#0f1115; --topbar-fg:#f2f4f8;
    --kw:#6cb6ff; --str:#ff9ec0; --cmt:#7fbf8f;
    --mark:#584a1a; --shadow:rgba(0,0,0,.4);
    color-scheme:dark;
  }
}
/* ผู้ใช้กดปุ่มเลือกเอง */
:root[data-theme="dark"]{
  --green:#2ec98c; --green-dark:#25b47c; --green-soft:#12291f; --green-border:#1f4e3a;
  --yellow:#ffd94d;
  --bg:#14161c; --text:#e6e8ee; --muted:#a7adba; --muted2:#8b93a3;
  --surface:#1a1d25; --surface-2:#20242e; --sidebar:#1a1d25; --sidebar-hover:#2b303c;
  --border:#333a49; --border-soft:#262b36;
  --code-bg:#20242e; --code-fg:#ff9ec0; --pre-bg:#11141a; --pre-fg:#e6e8ee;
  --link:#4fd6a0;
  --note-bg:#2e2712; --note-bd:#c9a227;
  --warn-bg:#331b1b; --warn-bd:#e06c6c;
  --tip-bg:#16233a;  --tip-bd:#5a95e8;
  --ok-bg:#132a1f;   --no-bg:#331b1b;
  --topbar:#0f1115; --topbar-fg:#f2f4f8;
  --kw:#6cb6ff; --str:#ff9ec0; --cmt:#7fbf8f;
  --mark:#584a1a; --shadow:rgba(0,0,0,.4);
  color-scheme:dark;
}

/* ---------- base ---------- */
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{
  margin:0;font-family:"Segoe UI","Sarabun","Noto Sans Thai",Verdana,sans-serif;
  font-size:16px;line-height:1.65;color:var(--text);background:var(--bg);
}
a{color:var(--link);text-decoration:none}
a:hover{text-decoration:underline}
code{font-family:Consolas,"Courier New",monospace;background:var(--code-bg);
  padding:1px 5px;border-radius:3px;font-size:.94em;color:var(--code-fg)}

/* ---------- top bar ---------- */
.topbar{position:sticky;top:0;z-index:50;background:var(--topbar);color:var(--topbar-fg);
  display:flex;align-items:center;gap:18px;padding:10px 18px;flex-wrap:wrap}
.topbar .logo{font-weight:800;font-size:20px;color:var(--topbar-fg)}
.topbar .logo span{color:var(--green)}
.topbar nav{display:flex;gap:6px;flex-wrap:wrap}
.topbar nav a{color:var(--topbar-fg);padding:6px 12px;border-radius:4px;font-size:14px}
.topbar nav a:hover{background:var(--green);color:#04121b;text-decoration:none}
.topbar nav a.active{background:var(--green);color:#04121b}

/* ---------- theme toggle ---------- */
.theme-toggle{margin-left:auto;background:transparent;color:var(--topbar-fg);
  border:1px solid rgba(255,255,255,.35);border-radius:20px;padding:5px 13px;
  cursor:pointer;font-size:13.5px;font-family:inherit;display:flex;align-items:center;gap:6px}
.theme-toggle:hover{background:rgba(255,255,255,.12)}

/* ---------- layout ---------- */
.layout{display:flex;align-items:flex-start}
.sidebar{width:250px;flex:0 0 250px;background:var(--sidebar);
  padding:16px 0 60px;position:sticky;top:52px;max-height:calc(100vh - 52px);overflow-y:auto;
  border-right:1px solid var(--border-soft)}
.sidebar h3{margin:14px 16px 6px;font-size:13px;letter-spacing:.06em;
  text-transform:uppercase;color:var(--muted)}
.sidebar a{display:block;padding:7px 16px;color:var(--text);font-size:15px;border-left:3px solid transparent}
.sidebar a:hover{background:var(--sidebar-hover);text-decoration:none}
.sidebar a.active{background:var(--green);color:#04121b;border-left-color:var(--green-dark);font-weight:600}
main{flex:1;min-width:0;padding:24px 34px 80px;max-width:980px}

/* ---------- content ---------- */
h1{font-size:38px;margin:.2em 0 .35em;font-weight:400}
h2{font-size:27px;margin:1.6em 0 .4em;font-weight:400;border-bottom:1px solid var(--border);padding-bottom:6px}
h3{font-size:20px;margin:1.3em 0 .3em}
h4{font-size:17px;margin:1.1em 0 .2em}
p{margin:.6em 0}
ul,ol{margin:.5em 0 .9em;padding-left:26px}
li{margin:.22em 0}

.lead{background:var(--green-soft);border-left:6px solid var(--green);
  padding:12px 16px;border-radius:0 4px 4px 0;margin:14px 0}
.note{background:var(--note-bg);border-left:6px solid var(--note-bd);padding:12px 16px;margin:14px 0;border-radius:0 4px 4px 0}
.warn{background:var(--warn-bg);border-left:6px solid var(--warn-bd);padding:12px 16px;margin:14px 0;border-radius:0 4px 4px 0}
.tip{background:var(--tip-bg);border-left:6px solid var(--tip-bd);padding:12px 16px;margin:14px 0;border-radius:0 4px 4px 0}

.example{background:var(--green-soft);border:1px solid var(--green-border);padding:14px 16px;margin:16px 0;border-radius:5px}
.example h4{margin:0 0 8px;font-size:16px;color:var(--green-dark)}
pre{background:var(--pre-bg);border:1px solid var(--border);padding:12px 14px;margin:8px 0;
  overflow-x:auto;border-radius:4px;font-family:Consolas,"Courier New",monospace;
  font-size:14.5px;line-height:1.5;color:var(--pre-fg);white-space:pre}
pre code{background:none;color:inherit;padding:0}
.kw{color:var(--kw);font-weight:600}
.str{color:var(--str)}
.cmt{color:var(--cmt);font-style:italic}

table{border-collapse:collapse;width:100%;margin:12px 0;font-size:14.5px;display:block;overflow-x:auto;
  background:var(--surface);color:var(--text)}
th,td{border:1px solid var(--border);padding:7px 10px;text-align:left;white-space:nowrap}
th{background:var(--green);color:#04121b;font-weight:600}
tbody tr:nth-child(even){background:var(--surface-2)}
td.null{color:var(--muted2);font-style:italic}
mark{background:var(--mark);color:var(--text);padding:0 3px}

.btn{display:inline-block;background:var(--green);color:#04121b;border:none;
  padding:9px 18px;border-radius:4px;cursor:pointer;font-size:15px;font-family:inherit;font-weight:600}
.btn:hover{background:var(--green-dark);text-decoration:none;color:#04121b}
.btn.ghost{background:var(--surface);color:var(--text);border:1px solid var(--border);font-weight:400}
.btn.ghost:hover{background:var(--surface-2);color:var(--text)}

.pager{display:flex;justify-content:space-between;margin:46px 0 0;gap:10px;flex-wrap:wrap}

/* ---------- try-it ---------- */
.tryit{border:1px solid var(--border);border-radius:5px;margin:16px 0;overflow:hidden;background:var(--surface)}
.tryit .head{background:var(--surface-2);padding:8px 12px;font-weight:600;font-size:14px;
  display:flex;justify-content:space-between;align-items:center;gap:10px}
.tryit textarea{width:100%;border:none;border-top:1px solid var(--border);
  padding:12px;font-family:Consolas,"Courier New",monospace;font-size:14.5px;
  resize:vertical;min-height:110px;outline:none;background:var(--pre-bg);color:var(--pre-fg)}
.tryit .out{border-top:1px solid var(--border);padding:12px;background:var(--surface-2);font-size:14.5px}

/* ---------- quiz ---------- */
.quizbox{border:2px solid var(--green);border-radius:8px;padding:18px 20px;margin:26px 0;background:var(--surface)}
.quizbox>h2{border:none;margin-top:0}
.q{border-bottom:1px solid var(--border);padding:16px 0}
.q:last-of-type{border-bottom:none}
.q .qhead{display:flex;gap:10px;align-items:flex-start}
.q .num{background:var(--green);color:#04121b;border-radius:50%;width:26px;height:26px;
  flex:0 0 26px;display:flex;align-items:center;justify-content:center;font-size:13px;font-weight:700}
.q .qtext{font-weight:600}
.tag{font-size:11px;letter-spacing:.05em;text-transform:uppercase;background:var(--topbar);color:var(--topbar-fg);
  padding:2px 7px;border-radius:10px;margin-left:8px;vertical-align:middle}
.tag.mcq{background:#2f6fd0;color:#fff}
.tag.fill{background:#b7791f;color:#fff}
.tag.code{background:#7048a8;color:#fff}
.opts{margin:10px 0 0 36px}
.opts label{display:block;padding:6px 10px;border:1px solid var(--border);border-radius:4px;
  margin:5px 0;cursor:pointer;background:var(--surface)}
.opts label:hover{background:var(--surface-2)}
.opts input{margin-right:9px}
.q .answer-area{margin:10px 0 0 36px}
.q input[type=text]{width:100%;max-width:520px;padding:8px 10px;border:1px solid var(--border);
  border-radius:4px;font-size:15px;font-family:inherit;background:var(--surface);color:var(--text)}
.q textarea{width:100%;padding:10px;border:1px solid var(--border);border-radius:4px;
  font-family:Consolas,"Courier New",monospace;font-size:14.5px;min-height:100px;
  background:var(--pre-bg);color:var(--pre-fg)}
.q .actions{margin:10px 0 0 36px;display:flex;gap:8px;flex-wrap:wrap}
.fb{margin:10px 0 0 36px;padding:10px 13px;border-radius:4px;font-size:14.6px;display:none}
.fb.ok{display:block;background:var(--ok-bg);border-left:5px solid var(--green)}
.fb.no{display:block;background:var(--no-bg);border-left:5px solid var(--warn-bd)}
.fb pre{margin:8px 0 0}
.score{margin-top:18px;padding:14px;background:var(--topbar);color:var(--topbar-fg);border-radius:6px;font-size:17px}
.score b{color:var(--yellow)}

.cards{display:grid;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));gap:16px;margin:20px 0}
.card{border:1px solid var(--border);border-radius:8px;padding:16px;background:var(--surface)}
.card h3{margin:0 0 6px;font-size:18px}
.card p{font-size:14.5px;color:var(--muted);margin:0 0 12px}

.hero{background:var(--green);color:#04121b;padding:40px 34px;text-align:center}
.hero h1{margin:0 0 8px;font-weight:700}
.hero p{margin:0;font-size:18px}

@media(max-width:860px){
  .layout{flex-direction:column}
  .sidebar{width:100%;flex:1 1 auto;position:static;max-height:none;border-right:none;
    border-bottom:1px solid var(--border-soft)}
  main{padding:18px}
  h1{font-size:29px}
  .theme-toggle{margin-left:0}
}

/* ================= diagrams ================= */
.dia{background:var(--surface-2);border:1px solid var(--border);border-radius:8px;
  padding:14px;margin:18px 0;overflow-x:auto}
.dia svg{display:block;max-width:100%;height:auto}
.dia .cap{font-size:13.5px;color:var(--muted);margin:8px 2px 0}
.dia text{font-family:"Segoe UI","Sarabun",sans-serif}
.dia .mono{font-family:Consolas,monospace}
.dia .lbl{fill:var(--text)}
.dia .dim{fill:var(--muted2)}
.dia .axis{stroke:var(--muted2);stroke-width:1.5}
.dia .grid{stroke:var(--border);stroke-width:1}
.dia .node{fill:var(--green-soft);stroke:var(--green);stroke-width:2}
.dia .node-txt{fill:var(--text);font-weight:600}
.dia .node-hi{fill:var(--green);stroke:var(--green-dark);stroke-width:2}
.dia .node-hi-txt{fill:#04121b;font-weight:700}
.dia .node-off{fill:var(--surface);stroke:var(--border);stroke-width:2;stroke-dasharray:4 3}
.dia .edge{stroke:var(--muted);stroke-width:2;fill:none}
.dia .edge-hi{stroke:var(--green);stroke-width:3.5;fill:none}
.dia .edge-cut{stroke:var(--warn-bd);stroke-width:2;stroke-dasharray:5 4;fill:none}
.dia .box{fill:var(--surface);stroke:var(--border);stroke-width:1.5}
.dia .box-fill{fill:var(--green-soft);stroke:var(--green);stroke-width:1.5}
.dia .box-warn{fill:var(--warn-bg);stroke:var(--warn-bd);stroke-width:1.5}
.dia .c-blue{stroke:#4f8ff0;fill:none;stroke-width:2.5}
.dia .c-green{stroke:var(--green);fill:none;stroke-width:2.5}
.dia .c-orange{stroke:#e08c3b;fill:none;stroke-width:2.5}
.dia .c-purple{stroke:#9b7ad6;fill:none;stroke-width:2.5}
.dia .c-red{stroke:var(--warn-bd);fill:none;stroke-width:2.5}
.dia .t-blue{fill:#4f8ff0}   .dia .t-green{fill:var(--green)}
.dia .t-orange{fill:#e08c3b} .dia .t-purple{fill:#9b7ad6}
.dia .t-red{fill:var(--warn-bd)}