/* ===== RESET & BASE ===== */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --cream:       #FAF7F2;
  --warm-white:  #FFFFFF;
  --parchment:   #F0EBE0;
  --sand:        #E8E0D0;
  --moss:        #4A6741;
  --moss-light:  #5C7D53;
  --moss-pale:   #E8F0E6;
  --amber:       #C8892A;
  --amber-light: #F5C967;
  --ink:         #1A1A14;
  --ink-mid:     #3D3D30;
  --ink-soft:    #6B6B58;
  --border:      #D8D0BE;
  --shadow:      rgba(74,103,65,0.10);
  --shadow-deep: rgba(26,26,20,0.12);

  --radius-sm: 6px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --font-serif: 'DM Serif Display', Georgia, serif;
  --font-mono:  'DM Mono', 'Courier New', monospace;
}

html { font-size: 16px; }

body {
  background: var(--cream);
  color: var(--ink);
  font-family: var(--font-mono);
  min-height: 100vh;
  position: relative;
  overflow-x: hidden;
}

/* ===== BACKGROUND TEXTURE ===== */
.bg-texture {
  position: fixed; inset: 0;
  background-image:
    radial-gradient(circle at 15% 20%, rgba(200,137,42,0.06) 0%, transparent 50%),
    radial-gradient(circle at 85% 75%, rgba(74,103,65,0.07) 0%, transparent 50%),
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='60' height='60'%3E%3Cpath d='M0 0h60v60H0z' fill='none'/%3E%3Ccircle cx='30' cy='30' r='0.5' fill='%234A6741' opacity='0.08'/%3E%3C/svg%3E");
  pointer-events: none;
  z-index: 0;
}

/* ===== HEADER ===== */
header {
  position: relative; z-index: 1;
  text-align: center;
  padding: 3rem 2rem 1.5rem;
  border-bottom: 1px solid var(--border);
}

.logo {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  margin-bottom: 0.4rem;
}

.logo-symbol {
  font-family: var(--font-serif);
  font-size: 2.4rem;
  color: var(--moss);
  line-height: 1;
  display: inline-block;
  animation: float 4s ease-in-out infinite;
}

@keyframes float {
  0%, 100% { transform: translateY(0); }
  50%       { transform: translateY(-4px); }
}

.logo-text {
  font-family: var(--font-serif);
  font-size: 2.2rem;
  color: var(--ink);
  letter-spacing: -0.02em;
}

.tagline {
  font-size: 0.78rem;
  color: var(--ink-soft);
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

/* ===== MAIN ===== */
main {
  position: relative; z-index: 1;
  max-width: 900px;
  margin: 0 auto;
  padding: 2rem 1.5rem 4rem;
  display: flex;
  flex-direction: column;
  gap: 2rem;
}

/* ===== OPERATION BAR ===== */
.op-bar {
  display: flex;
  gap: 0.5rem;
  background: var(--warm-white);
  padding: 0.4rem;
  border-radius: var(--radius-lg);
  border: 1px solid var(--border);
  box-shadow: 0 2px 8px var(--shadow);
  width: fit-content;
  margin: 0 auto;
}

.op-btn {
  padding: 0.55rem 1.6rem;
  border: none;
  border-radius: var(--radius-md);
  background: transparent;
  font-family: var(--font-serif);
  font-size: 1.05rem;
  color: var(--ink-soft);
  cursor: pointer;
  transition: all 0.2s ease;
  letter-spacing: 0.02em;
}

.op-btn:hover {
  background: var(--moss-pale);
  color: var(--moss);
}

.op-btn.active {
  background: var(--moss);
  color: var(--warm-white);
  box-shadow: 0 2px 8px rgba(74,103,65,0.25);
}

/* ===== MATRIX SECTION ===== */
.matrix-section {
  background: var(--warm-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.5rem;
  box-shadow: 0 4px 16px var(--shadow);
  animation: slideUp 0.4s ease both;
}

@keyframes slideUp {
  from { opacity: 0; transform: translateY(12px); }
  to   { opacity: 1; transform: translateY(0); }
}

.matrix-header {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.8rem;
  margin-bottom: 1.2rem;
}

.matrix-label {
  font-family: var(--font-serif);
  font-size: 1.4rem;
  color: var(--ink);
  margin-right: auto;
}

.matrix-label em {
  color: var(--moss);
  font-style: italic;
}

.result-label { color: var(--amber); }
.result-label em { color: var(--amber); }

/* ===== SIZE CONTROLS ===== */
.size-controls {
  display: flex;
  align-items: center;
  gap: 0.4rem;
  background: var(--parchment);
  padding: 0.35rem 0.8rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--sand);
}

.size-controls label {
  font-size: 0.7rem;
  color: var(--ink-soft);
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.sz-btn {
  width: 22px; height: 22px;
  border-radius: 50%;
  border: 1px solid var(--border);
  background: var(--warm-white);
  font-size: 1rem;
  line-height: 1;
  cursor: pointer;
  color: var(--moss);
  display: flex; align-items: center; justify-content: center;
  transition: all 0.15s;
  font-weight: 500;
}

.sz-btn:hover {
  background: var(--moss);
  color: white;
  border-color: var(--moss);
  transform: scale(1.1);
}

.sz-val {
  font-size: 0.9rem;
  font-weight: 500;
  min-width: 18px;
  text-align: center;
  color: var(--ink);
}

/* ===== ACTION BUTTON ===== */
.action-btn {
  padding: 0.35rem 0.85rem;
  border-radius: var(--radius-sm);
  border: 1px solid var(--border);
  background: var(--parchment);
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--ink-mid);
  cursor: pointer;
  transition: all 0.18s;
  letter-spacing: 0.03em;
}

.action-btn:hover {
  background: var(--moss-pale);
  border-color: var(--moss);
  color: var(--moss);
}

.copy-btn:hover {
  background: #FFF8E8;
  border-color: var(--amber);
  color: var(--amber);
}

/* ===== MATRIX GRID ===== */
.matrix-wrap {
  display: flex;
  align-items: center;
  gap: 0.3rem;
  overflow-x: auto;
  padding-bottom: 0.4rem;
}

.bracket {
  font-family: var(--font-serif);
  font-size: 4rem;
  color: var(--moss);
  line-height: 1;
  user-select: none;
  opacity: 0.7;
  flex-shrink: 0;
}

.matrix-grid {
  display: grid;
  gap: 6px;
  flex: 1;
}

.matrix-cell {
  width: 60px; height: 42px;
  border: 1.5px solid var(--sand);
  border-radius: var(--radius-sm);
  background: var(--cream);
  font-family: var(--font-mono);
  font-size: 0.88rem;
  color: var(--ink);
  text-align: center;
  transition: all 0.15s;
  outline: none;
}

.matrix-cell:focus {
  border-color: var(--moss);
  background: var(--moss-pale);
  box-shadow: 0 0 0 3px rgba(74,103,65,0.12);
}

.matrix-cell.result-cell {
  background: #FFF9F0;
  border-color: #F0DDA8;
  color: var(--amber);
  font-weight: 500;
  pointer-events: none;
  cursor: default;
}

/* ===== CALC ROW ===== */
.calc-row {
  display: flex;
  justify-content: center;
  gap: 1rem;
}

/* ===== SWAP ROW ===== */
.swap-row {
  display: flex;
  justify-content: center;
  margin: 1.5rem 0;
}

.swap-btn {
  padding: 0.7rem 1.8rem;
  background: var(--ink);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: 0.9rem;
  cursor: pointer;
  transition: all 0.2s;
  box-shadow: 0 3px 10px rgba(0,0,0,0.15);
  display: flex;
  align-items: center;
  gap: 0.5rem;
}

.swap-btn:hover {
  background: var(--ink-soft);
  transform: translateY(-2px);
  box-shadow: 0 5px 15px rgba(0,0,0,0.2);
}

.swap-btn:active { transform: translateY(0); }

.calc-btn {
  padding: 0.9rem 3rem;
  background: var(--moss);
  color: white;
  border: none;
  border-radius: var(--radius-md);
  font-family: var(--font-serif);
  font-size: 1.15rem;
  cursor: pointer;
  transition: all 0.2s;
  box-shadow: 0 4px 14px rgba(74,103,65,0.3);
  letter-spacing: 0.02em;
}

.calc-btn:hover {
  background: var(--moss-light);
  transform: translateY(-2px);
  box-shadow: 0 6px 20px rgba(74,103,65,0.35);
}

.calc-btn:active { transform: translateY(0); }

.clear-btn {
  padding: 0.9rem 2rem;
  background: transparent;
  color: var(--ink-soft);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-md);
  font-family: var(--font-mono);
  font-size: 0.85rem;
  cursor: pointer;
  transition: all 0.2s;
}

.clear-btn:hover {
  border-color: #C0392B;
  color: #C0392B;
  background: #FFF5F5;
}

/* ===== MESSAGE BOX ===== */
.message-box {
  padding: 0.9rem 1.2rem;
  border-radius: var(--radius-md);
  font-size: 0.85rem;
  line-height: 1.5;
  animation: fadeIn 0.3s ease;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(-6px); }
  to   { opacity: 1; transform: translateY(0); }
}

.message-box.error {
  background: #FFF0F0;
  border: 1px solid #F5BFBF;
  color: #8B2020;
}

.message-box.success {
  background: var(--moss-pale);
  border: 1px solid #BDD4B8;
  color: var(--moss);
}

/* ===== RESULT SECTION ===== */
.result-section {
  border-color: #F0DDA8;
  box-shadow: 0 4px 20px rgba(200,137,42,0.12);
  animation: resultReveal 0.5s cubic-bezier(0.34,1.56,0.64,1) both;
}

@keyframes resultReveal {
  from { opacity: 0; transform: scale(0.96) translateY(10px); }
  to   { opacity: 1; transform: scale(1) translateY(0); }
}

/* ===== SEO HEADINGS (visible but styled subtly) ===== */
.seo-heading {
  font-family: var(--font-serif);
  font-size: 1.6rem;
  color: var(--ink);
  text-align: center;
  letter-spacing: -0.01em;
  margin-top: 0.5rem;
}

.seo-subheading {
  text-align: center;
  font-size: 0.82rem;
  color: var(--ink-soft);
  max-width: 520px;
  margin: 0.4rem auto 0;
  line-height: 1.6;
}

/* ===== SKIP LINK (accessibility) ===== */
.skip-link {
  position: absolute;
  top: -100px;
  left: 1rem;
  background: var(--moss);
  color: white;
  padding: 0.5rem 1rem;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  text-decoration: none;
  z-index: 1000;
  transition: top 0.2s;
}
.skip-link:focus { top: 1rem; }

/* ===== FAQ SECTION ===== */
.faq-section {
  background: var(--warm-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-lg);
  padding: 1.8rem;
  box-shadow: 0 4px 16px var(--shadow);
}

.faq-section h2 {
  font-family: var(--font-serif);
  font-size: 1.3rem;
  color: var(--ink);
  margin-bottom: 1rem;
  letter-spacing: -0.01em;
}

.faq-section details {
  border-bottom: 1px solid var(--sand);
  padding: 0.8rem 0;
}

.faq-section details:last-child { border-bottom: none; }

.faq-section summary {
  font-size: 0.9rem;
  font-weight: 500;
  color: var(--ink-mid);
  cursor: pointer;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
  transition: color 0.15s;
}

.faq-section summary::-webkit-details-marker { display: none; }

.faq-section summary::before {
  content: '+';
  font-size: 1.1rem;
  color: var(--moss);
  font-weight: 300;
  flex-shrink: 0;
  transition: transform 0.2s;
}

.faq-section details[open] summary::before {
  content: '−';
}

.faq-section summary:hover { color: var(--moss); }

.faq-section p {
  margin-top: 0.6rem;
  font-size: 0.82rem;
  color: var(--ink-soft);
  line-height: 1.65;
  padding-left: 1.4rem;
}

/* ===== HOW TO USE ===== */
.howto-section {
  position: relative; z-index: 1;
  max-width: 680px;
  margin: 2rem auto 0;
  padding: 1.5rem 2rem;
  background: var(--warm-white);
  border: 1px solid var(--border);
  border-radius: var(--radius-md);
}

.howto-section h2 {
  font-family: var(--font-serif);
  font-size: 1.1rem;
  color: var(--ink);
  margin-bottom: 1rem;
}

.howto-steps {
  padding-left: 1.4rem;
  display: flex;
  flex-direction: column;
  gap: 0.55rem;
}

.howto-steps li {
  font-size: 0.82rem;
  color: var(--ink-soft);
  line-height: 1.65;
}

.howto-steps li strong {
  color: var(--ink);
}

/* ===== FOOTER ===== */
footer {
  position: relative; z-index: 1;
  text-align: center;
  padding: 1.5rem;
  border-top: 1px solid var(--border);
  font-size: 0.75rem;
  color: var(--ink-soft);
  letter-spacing: 0.08em;
}

.footer-links {
  margin-top: 0.4rem;
}

.footer-links a {
  color: var(--moss);
  text-decoration: none;
  font-size: 0.72rem;
}

.footer-links a:hover { text-decoration: underline; }

/* ===== MATRICES CONTAINER ===== */
.matrices-container {
  display: flex;
  flex-direction: column;
  gap: 1.5rem;
}

@media (min-width: 900px) {
  .matrices-container {
    flex-direction: row;
    align-items: flex-start;
    justify-content: center;
    gap: 2rem;
  }
  .matrices-container .matrix-section {
    flex: 1;
    max-width: 420px;
  }
  .matrices-container .swap-row {
    margin: 0;
    align-self: center;
  }
}

/* ===== RESPONSIVE ===== */
@media (max-width: 600px) {
  .matrix-header { flex-direction: column; align-items: flex-start; }
  .matrix-cell { width: 48px; height: 38px; font-size: 0.8rem; }
  .calc-btn { padding: 0.8rem 2rem; font-size: 1rem; }
  .op-btn { padding: 0.5rem 1rem; font-size: 0.95rem; }
}