:root {
  --bg: #f7f2e8;
  --surface: #ffffff;
  --surface-alt: #fdf8f2;
  --border: #e6d7c3;
  --text: #262523;
  --muted: #6b7280;
  --primary: #2a9d8f;
  --primary-dark: #1f8074;
  --accent: #f4a261;
  --success: #2f9e44;
  --warning: #f59f00;
  --danger: #e63946;
  --shadow: 0 20px 45px -28px rgba(38, 30, 22, 0.35);
  --font-display: "Fraunces", "Iowan Old Style", "Palatino Linotype", serif;
  --font-body: "IBM Plex Sans", "Avenir Next", "Segoe UI", sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1316;
    --surface: #151a1f;
    --surface-alt: #1b222a;
    --border: #2b333c;
    --text: #f1f5f9;
    --muted: #9aa4b2;
    --primary: #4dd4c4;
    --primary-dark: #2fb7a8;
    --accent: #ffb37a;
    --success: #4ade80;
    --warning: #fbbf24;
    --danger: #f87171;
    --shadow: 0 20px 50px -30px rgba(0, 0, 0, 0.6);
  }
}

* {
  box-sizing: border-box;
}

body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(circle at 15% 0%, rgba(244, 162, 97, 0.2), transparent 45%),
    radial-gradient(circle at 85% 10%, rgba(42, 157, 143, 0.2), transparent 55%),
    var(--bg);
  color: var(--text);
  font: 15px/1.6 var(--font-body);
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  background-image:
    linear-gradient(transparent 0, transparent 23px, rgba(0, 0, 0, 0.03) 24px),
    linear-gradient(90deg, transparent 0, transparent 23px, rgba(0, 0, 0, 0.03) 24px);
  background-size: 24px 24px;
  opacity: 0.35;
  pointer-events: none;
  z-index: -1;
}

@media (prefers-color-scheme: dark) {
  body::before {
    background-image:
      linear-gradient(transparent 0, transparent 23px, rgba(255, 255, 255, 0.05) 24px),
      linear-gradient(90deg, transparent 0, transparent 23px, rgba(255, 255, 255, 0.05) 24px);
  }
}

.container {
  max-width: 1120px;
  margin: 0 auto;
  padding: 32px 20px 60px;
}

.header {
  text-align: center;
  margin-bottom: 32px;
  padding: 28px 24px;
  border-radius: 24px;
  background: linear-gradient(135deg, rgba(42, 157, 143, 0.15), rgba(244, 162, 97, 0.18));
  border: 1px solid var(--border);
  box-shadow: var(--shadow);
}

.header h1 {
  font-family: var(--font-display);
  font-size: clamp(2rem, 3vw, 2.8rem);
  margin: 0 0 10px;
}

.subtitle {
  margin: 0;
  color: var(--muted);
  font-size: 1.05rem;
}

.hint {
  margin-top: 10px;
  color: var(--muted);
  font-size: 0.9rem;
}

.grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 20px;
}

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 20px;
  padding: 22px 22px 24px;
  box-shadow: var(--shadow);
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.card-head {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.card h2 {
  margin: 0;
  font-size: 1.35rem;
  display: flex;
  align-items: center;
  gap: 10px;
  font-family: var(--font-display);
}

.card-desc {
  margin: 6px 0 0;
  font-size: 0.95rem;
  color: var(--muted);
}

.toggle {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 600;
  color: var(--text);
  background: var(--surface-alt);
  border: 1px solid var(--border);
  padding: 8px 12px;
  border-radius: 999px;
}

.toggle input {
  appearance: none;
  width: 42px;
  height: 22px;
  border-radius: 999px;
  background: var(--border);
  position: relative;
  cursor: pointer;
  transition: background 0.2s ease;
}

.toggle input::after {
  content: "";
  position: absolute;
  top: 2px;
  left: 2px;
  width: 18px;
  height: 18px;
  border-radius: 50%;
  background: var(--surface);
  transition: transform 0.2s ease;
}

.toggle input:checked {
  background: var(--primary);
}

.toggle input:checked::after {
  transform: translateX(20px);
}

.preset-bar {
  display: flex;
  flex-direction: column;
  gap: 8px;
  background: rgba(42, 157, 143, 0.12);
  border: 1px solid rgba(42, 157, 143, 0.3);
  border-radius: 14px;
  padding: 12px 14px;
}

.preset-bar label span {
  font-weight: 600;
  color: var(--text);
}

#buffer-preset {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: inherit;
  font: inherit;
}

#buffer-preset:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
  border-color: var(--primary);
}

.preset-hint {
  margin: 0;
  font-size: 0.85rem;
  color: var(--muted);
}

.form-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 14px 16px;
}

label {
  display: flex;
  flex-direction: column;
  gap: 6px;
  font-weight: 600;
  color: var(--text);
}

.input-row {
  display: flex;
  gap: 8px;
  align-items: center;
}

input[type="number"],
select {
  padding: 10px 12px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: inherit;
  font: inherit;
  transition: border-color 0.2s ease, box-shadow 0.2s ease;
}

.input-row input {
  flex: 1;
}

.input-row select {
  width: 90px;
}

input[type="number"]:focus-visible,
select:focus-visible {
  outline: 2px solid var(--primary);
  outline-offset: 2px;
  border-color: var(--primary);
  box-shadow: 0 0 0 4px rgba(42, 157, 143, 0.2);
}

input.input-invalid {
  border-color: var(--danger) !important;
  box-shadow: 0 0 0 3px rgba(230, 57, 70, 0.2);
}

.row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
}

.btn {
  padding: 10px 18px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface-alt);
  color: inherit;
  font-weight: 600;
  cursor: pointer;
  transition: transform 0.15s ease, box-shadow 0.15s ease, border-color 0.15s ease;
}

.btn:hover {
  transform: translateY(-1px);
  border-color: var(--primary);
}

.btn.primary {
  background: linear-gradient(120deg, var(--primary), var(--primary-dark));
  color: #fff;
  border-color: transparent;
}

.btn.primary:hover {
  box-shadow: 0 12px 25px -18px rgba(42, 157, 143, 0.8);
}

.btn.copy {
  background: var(--success);
  border-color: var(--success);
  color: #fff;
}

.btn.copy:hover {
  box-shadow: 0 10px 20px -16px rgba(47, 158, 68, 0.7);
}

.btn.ghost {
  border-style: dashed;
  color: var(--muted);
}

.btn.ghost:hover {
  color: var(--text);
}

.result {
  min-height: 40px;
  padding: 14px 16px;
  background: linear-gradient(135deg, rgba(42, 157, 143, 0.12), rgba(244, 162, 97, 0.12));
  border: 1px solid rgba(42, 157, 143, 0.35);
  border-radius: 12px;
  font-weight: 600;
  white-space: pre-line;
}

.result:empty {
  display: none;
}

.steps {
  font-size: 0.88rem;
  color: var(--muted);
  background: rgba(42, 157, 143, 0.08);
  border-radius: 12px;
  padding: 12px 14px;
  display: none;
  line-height: 1.6;
}

.steps:not(:empty) {
  display: block;
}

.serial-warning {
  color: var(--warning);
  font-weight: 700;
}

.toast {
  position: fixed;
  top: 20px;
  right: 20px;
  background: var(--primary);
  color: #fff;
  padding: 12px 18px;
  border-radius: 12px;
  box-shadow: 0 12px 28px -16px rgba(42, 157, 143, 0.9);
  z-index: 9999;
  opacity: 0.95;
}

.toast.error {
  background: var(--danger);
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

@media (max-width: 680px) {
  .container {
    padding: 26px 14px 40px;
  }

  .card {
    padding: 20px;
  }

  .row {
    flex-direction: column;
  }

  .btn {
    width: 100%;
    text-align: center;
  }

  .preset-bar {
    padding: 10px 12px;
  }

  .toggle {
    width: 100%;
    justify-content: space-between;
  }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}