:root{
  --bg:#06030c; --red:#a3121b; --red2:#6f0b12; --gold:#d4af37;
  --paper:#f2ead8; --ink:#1b1b1b;
}
*{box-sizing:border-box}
body{
  margin:0; min-height:100vh; color:#fff;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, "Noto Sans Thai", Arial;
  background: radial-gradient(1200px 800px at 70% 20%, #1a0b22 0%, var(--bg) 60%, #000 100%);
}
.bg{min-height:100vh; display:grid; place-items:center; padding:22px}
.wrap{width:min(980px,100%)}
.top h1{margin:0; letter-spacing:.5px}
.sub{margin:6px 0 0; opacity:.8; font-size:13px}

.panel{
  margin-top:16px;
  background: rgba(255,255,255,.04);
  border: 1px solid rgba(255,255,255,.12);
  border-radius:18px;
  padding:16px;
}
.label{display:block; font-size:13px; opacity:.9; margin-bottom:8px}
.row{display:flex; gap:10px; flex-wrap:wrap}
input{
  flex:1; min-width:220px;
  padding:12px 14px;
  border-radius:12px;
  border:1px solid rgba(255,255,255,.18);
  background: rgba(0,0,0,.25);
  color:#fff; outline:none;
}
input:focus{border-color: rgba(212,175,55,.6)}
.btn{
  padding:12px 14px;
  border-radius:12px;
  border:1px solid rgba(212,175,55,.55);
  background: linear-gradient(180deg, rgba(212,175,55,.18), rgba(163,18,27,.30));
  color:#fff; cursor:pointer; font-weight:800;
}
.btn:disabled{opacity:.55; cursor:not-allowed}
.msg{min-height:18px; margin-top:10px; font-size:13px}
.msg.ok{color:#c7ffdf}
.msg.err{color:#ffd1d1}
.msg.warn{color:#ffe7b3}

.stage{display:grid; place-items:center; padding:14px 0}
.envelope{width:320px; height:220px; position:relative}
.env-back{
  position:absolute; inset:0; border-radius:18px;
  background: linear-gradient(145deg, var(--red), var(--red2));
  border:1px solid rgba(255,255,255,.12);
  box-shadow: 0 20px 55px rgba(0,0,0,.55);
}
.env-front{
  position:absolute; inset:0; border-radius:18px;
  background: linear-gradient(145deg, #8b0f18, #5f0910);
  clip-path: polygon(0 42%, 50% 82%, 100% 42%, 100% 100%, 0 100%);
  border:1px solid rgba(255,255,255,.08);
}
.seal{
  position:absolute; left:50%; top:52%;
  transform:translate(-50%,-50%);
  padding:10px 14px; border-radius:999px;
  border:1px solid rgba(212,175,55,.55);
  color: var(--gold); font-size:12px; letter-spacing:1px;
  background: radial-gradient(circle at 30% 30%, rgba(255,255,255,.12), rgba(0,0,0,.15));
}
.paper{
  position:absolute; left:50%; bottom:34px;
  transform:translateX(-50%) translateY(40px);
  width:260px; padding:14px;
  background: linear-gradient(180deg, #fff7e8, var(--paper));
  color: var(--ink);
  border-radius:16px;
  border:1px solid rgba(0,0,0,.12);
  box-shadow: 0 18px 40px rgba(0,0,0,.35);
  opacity:0;
}
.paper-title{font-weight:900; letter-spacing:.4px}
.paper-body{margin-top:10px; font-size:14px; line-height:1.45}
.paper-foot{margin-top:10px; font-size:12px; opacity:.75}

.envelope.open .paper{animation: slip 850ms cubic-bezier(.2,.9,.2,1) forwards;}
@keyframes slip{
  0%{opacity:0; transform:translateX(-50%) translateY(44px)}
  55%{opacity:1}
  100%{opacity:1; transform:translateX(-50%) translateY(-18px)}
}

.meta{display:flex; gap:10px; flex-wrap:wrap; margin-top:8px}
.chip{
  padding:8px 10px; border-radius:999px; font-size:12px;
  background: rgba(255,255,255,.06);
  border:1px solid rgba(255,255,255,.12);
}
.chip.gold{border-color: rgba(212,175,55,.35)}
.note{opacity:.7; font-size:12px; margin:10px 0 0}