:root {
  --bg: #0d1117;
  --bg-elev: #161b22;
  --bg-elev-2: #1f262f;
  --text: #e6edf3;
  --text-dim: #8b949e;
  --border: #30363d;
  --accent: #58a6ff;
  --accent-hover: #79b8ff;
  --success: #3fb950;
  --warn: #d29922;
  --danger: #f85149;
  --shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  --radius: 10px;
}

[data-theme="light"] {
  --bg: #f6f8fa;
  --bg-elev: #ffffff;
  --bg-elev-2: #f0f3f6;
  --text: #1f2328;
  --text-dim: #59636e;
  --border: #d0d7de;
  --accent: #0969da;
  --accent-hover: #0858b8;
  --success: #1a7f37;
  --warn: #9a6700;
  --danger: #cf222e;
  --shadow: 0 4px 16px rgba(140, 149, 159, 0.2);
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
  transition: background 0.2s ease, color 0.2s ease;
}

body { display: flex; flex-direction: column; min-height: 100vh; }

.container {
  max-width: 960px;
  margin: 0 auto;
  padding: 0 24px;
  width: 100%;
}

.header {
  border-bottom: 1px solid var(--border);
  background: var(--bg-elev);
  position: sticky;
  top: 0;
  z-index: 10;
  backdrop-filter: blur(8px);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 16px 24px;
}

.brand { display: flex; align-items: center; gap: 12px; }

.brand-mark {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  background: linear-gradient(135deg, var(--accent), #a371f7);
  color: white;
  border-radius: 8px;
  font-weight: 700;
  font-size: 20px;
}

.brand h1 {
  font-size: 18px;
  margin: 0;
  font-weight: 600;
  letter-spacing: -0.01em;
}

.theme-toggle {
  background: var(--bg-elev-2);
  color: var(--text);
  border: 1px solid var(--border);
  width: 38px;
  height: 38px;
  border-radius: 8px;
  cursor: pointer;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  font-size: 16px;
  transition: all 0.15s ease;
}

.theme-toggle:hover { border-color: var(--accent); color: var(--accent); }

.main { flex: 1; padding: 32px 0 48px; }

.lede {
  color: var(--text-dim);
  margin: 0 0 24px;
  font-size: 15px;
}

.lede strong { color: var(--text); }

.tabs {
  display: flex;
  gap: 4px;
  margin-bottom: 16px;
  border-bottom: 1px solid var(--border);
}

.tab {
  background: transparent;
  color: var(--text-dim);
  border: none;
  padding: 10px 18px;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  border-bottom: 2px solid transparent;
  margin-bottom: -1px;
  transition: all 0.15s ease;
}

.tab:hover { color: var(--text); }
.tab.active { color: var(--accent); border-bottom-color: var(--accent); }

.panel { display: none; }
.panel.active { display: block; }

.card {
  background: var(--bg-elev);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
}

.label {
  display: block;
  font-size: 13px;
  font-weight: 600;
  margin-bottom: 8px;
  color: var(--text);
}

.label-inline {
  font-size: 13px;
  color: var(--text-dim);
  margin-right: 8px;
}

textarea, input[type="text"], select {
  width: 100%;
  background: var(--bg);
  color: var(--text);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 14px;
  font-size: 14px;
  font-family: inherit;
  resize: vertical;
  transition: border-color 0.15s ease, box-shadow 0.15s ease;
}

textarea:focus, input:focus, select:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(88, 166, 255, 0.2);
}

select { cursor: pointer; }

.row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  margin-top: 16px;
  flex-wrap: wrap;
}

.algo-group { display: flex; align-items: center; flex: 1; min-width: 220px; }
.algo-group select { flex: 1; }

.btn-group { display: flex; gap: 8px; }

.btn {
  padding: 10px 18px;
  border-radius: 8px;
  border: 1px solid transparent;
  font-size: 14px;
  font-weight: 500;
  cursor: pointer;
  font-family: inherit;
  transition: all 0.15s ease;
}

.btn-primary {
  background: var(--accent);
  color: white;
}
.btn-primary:hover { background: var(--accent-hover); }

.btn-ghost {
  background: transparent;
  border-color: var(--border);
  color: var(--text);
}
.btn-ghost:hover { background: var(--bg-elev-2); }

.results { margin-top: 20px; display: flex; flex-direction: column; gap: 10px; }

.result-item {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 8px;
  padding: 12px 14px;
  display: flex;
  align-items: center;
  gap: 12px;
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 13px;
  word-break: break-all;
}

.result-algo {
  flex-shrink: 0;
  background: var(--bg-elev-2);
  color: var(--accent);
  padding: 4px 10px;
  border-radius: 5px;
  font-size: 11px;
  font-weight: 700;
  letter-spacing: 0.04em;
  font-family: inherit;
  min-width: 72px;
  text-align: center;
}

.result-value { flex: 1; color: var(--text); }

.copy-btn {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text-dim);
  padding: 4px 10px;
  border-radius: 5px;
  cursor: pointer;
  font-size: 12px;
  font-family: inherit;
  transition: all 0.15s ease;
  flex-shrink: 0;
}
.copy-btn:hover { color: var(--accent); border-color: var(--accent); }
.copy-btn.copied { color: var(--success); border-color: var(--success); }

.decode-success {
  background: var(--bg);
  border: 1px solid var(--success);
  border-radius: 8px;
  padding: 16px;
}

.decode-success .label-line {
  color: var(--success);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  margin-bottom: 6px;
}

.decode-success .plaintext {
  font-family: "SF Mono", Menlo, Consolas, monospace;
  font-size: 16px;
  color: var(--text);
  word-break: break-all;
}

.decode-fail {
  background: var(--bg);
  border: 1px solid var(--warn);
  border-radius: 8px;
  padding: 16px;
  color: var(--text-dim);
  font-size: 14px;
}
.decode-fail .label-line {
  color: var(--warn);
  font-size: 12px;
  font-weight: 700;
  letter-spacing: 0.04em;
  margin-bottom: 6px;
}

.note {
  margin-top: 16px;
  font-size: 12px;
  color: var(--text-dim);
  line-height: 1.5;
}

.footer {
  border-top: 1px solid var(--border);
  background: var(--bg-elev);
  padding: 20px 0;
  text-align: center;
  font-size: 13px;
  color: var(--text-dim);
}

.footer a {
  color: var(--accent);
  text-decoration: none;
  font-weight: 500;
}
.footer a:hover { text-decoration: underline; }

@media (max-width: 600px) {
  .container { padding: 0 16px; }
  .card { padding: 18px; }
  .row { flex-direction: column; align-items: stretch; }
  .btn-group { justify-content: flex-end; }
  .result-item { flex-direction: column; align-items: flex-start; }
}