:root{
  --bg:#e9e9e7;
  --surface:#ffffff;
  --ink:#141414;
  --muted:#6b6b6b;
  --line:#ececec;
  --teal:#19c2c2;
  --teal-soft:#d9f4f6;
  --teal-ink:#0c7d86;
  --danger:#b3261e;
  --danger-soft:#fdecea;
  --radius-lg:28px;
  --radius-md:18px;
  --radius-sm:12px;
}
*{margin:0;padding:0;box-sizing:border-box}
body{
  font-family:'Inter',-apple-system,'Segoe UI',Roboto,sans-serif;
  background:var(--bg);
  color:var(--ink);
  padding:14px;
  -webkit-font-smoothing:antialiased;
}
.shell{
  max-width:1240px;
  margin:0 auto;
  background:var(--surface);
  border-radius:var(--radius-lg);
  overflow:hidden;
}

/* ===== Header ===== */
header{
  display:flex;align-items:center;justify-content:space-between;
  gap:16px;padding:22px 36px;
}
.brand{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink)}
.brand .mark{
  width:34px;height:34px;border-radius:50%;
  border:2.5px solid var(--ink);
  display:grid;place-items:center;
  font-weight:800;font-size:16px;
}
.brand .name{font-weight:700;font-size:13px;letter-spacing:.14em;text-transform:uppercase}
.pill{
  background:var(--teal-soft);color:var(--teal-ink);
  font-size:11px;font-weight:700;letter-spacing:.1em;text-transform:uppercase;
  padding:7px 14px;border-radius:999px;
}

/* ===== Hero ===== */
.hero{padding:26px 36px 34px}
.eyebrow{
  display:inline-block;
  background:var(--teal-soft);color:var(--teal-ink);
  font-size:11px;font-weight:700;letter-spacing:.16em;text-transform:uppercase;
  padding:7px 14px;border-radius:999px;
  margin-bottom:18px;
}
.hero h1{
  font-size:clamp(32px,5.4vw,56px);
  font-weight:900;line-height:1.05;letter-spacing:-.02em;
  max-width:18ch;
}
.hero h1 em{font-style:normal;color:var(--teal-ink)}
.hero p{margin-top:16px;color:var(--muted);font-size:16px;line-height:1.6;max-width:60ch}

/* ===== Tabs ===== */
.tabs{
  display:flex;gap:8px;
  padding:0 36px;
  border-bottom:1px solid var(--line);
}
.tab{
  display:inline-flex;align-items:center;gap:9px;
  background:none;border:none;
  font-family:inherit;font-size:15px;font-weight:700;
  color:var(--muted);cursor:pointer;
  padding:14px 18px;
  border-bottom:3px solid transparent;
  margin-bottom:-1px;
  transition:color .15s ease,border-color .15s ease;
}
.tab svg{width:18px;height:18px}
.tab:hover{color:var(--ink)}
.tab.is-active{color:var(--ink);border-bottom-color:var(--teal)}

/* ===== Layout ===== */
.work{
  display:grid;
  grid-template-columns:minmax(0,1fr) 400px;
  gap:36px;
  padding:32px 36px 40px;
  align-items:start;
}

/* ===== Form ===== */
.panel{display:none}
.panel.is-active{display:block}
.form-group{display:none}
.form-group.is-active{display:block}

.field{margin-bottom:16px;min-width:0}
.field label,.check{
  display:block;
  font-size:13px;font-weight:700;
  margin-bottom:7px;
}
.row{display:grid;grid-template-columns:1fr 1fr;gap:14px}

input[type=text],input[type=number],select,textarea{
  width:100%;
  font-family:inherit;font-size:15px;color:var(--ink);
  background:#fbfbfa;
  border:1.5px solid var(--line);
  border-radius:var(--radius-sm);
  padding:11px 13px;
  transition:border-color .15s ease,background .15s ease;
}
textarea{resize:vertical;line-height:1.5}
input:focus,select:focus,textarea:focus{
  outline:none;
  border-color:var(--teal);
  background:#fff;
}
select{
  appearance:none;
  background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='%236b6b6b'%3E%3Cpath d='M7 10l5 5 5-5z'/%3E%3C/svg%3E");
  background-repeat:no-repeat;
  background-position:right 8px center;
  background-size:20px;
  padding-right:34px;
}
input[type=color]{
  width:100%;height:44px;
  padding:4px;
  background:#fbfbfa;
  border:1.5px solid var(--line);
  border-radius:var(--radius-sm);
  cursor:pointer;
}
.check{
  display:flex;align-items:center;gap:9px;
  font-weight:600;margin:0 0 12px;
  cursor:pointer;
}
.check input{width:17px;height:17px;accent-color:var(--teal-ink);cursor:pointer}

.hint{font-size:12.5px;color:var(--muted);line-height:1.5;margin-top:7px}
.hint code{
  background:#f2f2f1;border-radius:5px;padding:1px 5px;
  font-size:12px;
}

.advanced{
  border:1px solid var(--line);
  border-radius:var(--radius-md);
  padding:0 16px;
  margin-top:22px;
  background:#fbfbfa;
}
.advanced summary{
  font-size:14px;font-weight:700;
  padding:14px 0;
  cursor:pointer;
  list-style:none;
  display:flex;align-items:center;gap:8px;
}
.advanced summary::-webkit-details-marker{display:none}
.advanced summary::before{
  content:'';
  width:8px;height:8px;
  border-right:2px solid var(--muted);
  border-bottom:2px solid var(--muted);
  transform:rotate(-45deg);
  transition:transform .18s ease;
}
.advanced[open] summary::before{transform:rotate(45deg)}
.advanced[open]{padding-bottom:6px}

/* Không đặt display ở đây — sẽ đè mất thuộc tính [hidden] của thẻ. */
.warn{
  background:var(--danger-soft);color:var(--danger);
  border-radius:var(--radius-sm);
  padding:12px 14px;
  font-size:14px;line-height:1.5;font-weight:600;
  margin-top:18px;
}

/* ===== Preview ===== */
.preview-inner{position:sticky;top:14px}
.stage{
  border:1px solid var(--line);
  border-radius:var(--radius-md);
  background:#fff;
  padding:22px;
  display:grid;place-items:center;
  min-height:300px;
}
/* Ô ca-rô chỉ bật khi người dùng chọn nền trong suốt, để thấy rõ phần nào là trống. */
.stage.is-alpha{
  background:
    linear-gradient(45deg,#f0f0ef 25%,transparent 25%) 0 0/20px 20px,
    linear-gradient(-45deg,#f0f0ef 25%,transparent 25%) 0 10px/20px 20px,
    linear-gradient(45deg,transparent 75%,#f0f0ef 75%) 10px -10px/20px 20px,
    linear-gradient(-45deg,transparent 75%,#f0f0ef 75%) -10px 0/20px 20px,
    #fff;
}
.stage-box{
  width:100%;
  display:grid;place-items:center;
  overflow:hidden;
}
.stage-box svg{max-width:100%;height:auto;display:block}
.stage.is-empty .stage-box::after{
  content:'Nhập nội dung để xem mã';
  color:var(--muted);font-size:14px;
}
.meta{
  text-align:center;
  font-size:12.5px;color:var(--muted);
  margin-top:12px;min-height:19px;
}
.actions{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:10px;
  margin-top:16px;
}
.btn{
  display:inline-flex;align-items:center;justify-content:center;gap:8px;
  background:var(--ink);color:#fff;
  border:1.5px solid var(--ink);
  border-radius:999px;
  padding:12px 18px;
  font-family:inherit;font-size:14px;font-weight:700;
  text-decoration:none;cursor:pointer;
  transition:opacity .15s ease,background .15s ease,color .15s ease;
}
.btn svg{width:17px;height:17px}
.btn:hover{opacity:.85}
.btn.ghost{background:#fff;color:var(--ink);border-color:var(--line)}
.btn.ghost:hover{background:#f7f7f6;opacity:1;border-color:#dcdcdc}
.btn[disabled]{opacity:.4;cursor:not-allowed}
.btn[disabled]:hover{opacity:.4}
.toast{
  margin-top:12px;text-align:center;
  font-size:13px;font-weight:600;color:var(--teal-ink);
}

/* ===== Notes ===== */
.notes{
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(240px,1fr));
  gap:20px;
  padding:0 36px 40px;
}
.note{
  border:1px solid var(--line);
  border-radius:var(--radius-md);
  padding:20px;
  background:#fbfbfa;
}
.note h3{font-size:15px;font-weight:800;margin-bottom:8px}
.note p{font-size:14px;line-height:1.6;color:var(--muted)}
.note strong{color:var(--ink);font-weight:700}

footer{
  padding:26px 36px 34px;
  border-top:1px solid #eee;
  display:flex;justify-content:space-between;align-items:center;
  gap:14px;flex-wrap:wrap;
  font-size:13px;color:var(--muted);
}
footer a{color:var(--ink);text-decoration:none;font-weight:600}
footer a:hover{color:var(--teal-ink)}

/* ===== Responsive ===== */
@media (max-width:940px){
  .work{grid-template-columns:1fr;gap:28px}
  .preview-inner{position:static}
}
@media (max-width:640px){
  body{padding:8px}
  header{padding:18px 20px}
  .pill{display:none}
  .hero{padding:20px 20px 26px}
  .tabs{padding:0 12px}
  .tab{padding:13px 12px;font-size:14px}
  .work{padding:24px 20px 30px}
  .notes{padding:0 20px 30px}
  footer{padding:22px 20px 28px}
  .row{grid-template-columns:1fr}
}

/* ===== In ===== */
@media print{
  body{background:#fff;padding:0}
  header,.hero,.tabs,.controls,.notes,footer,.actions,.meta{display:none !important}
  .shell{border-radius:0}
  .work{display:block;padding:0}
  .stage{border:none;background:#fff;padding:0}
}