:root {
  --bg: #0A0E16;
  --surface: #121826;
  --surface-2: #1A2233;
  --surface-3: #212B40;
  --border: #262F45;
  --text: #E8ECF4;
  --muted: #8B96AC;
  --muted-2: #5D6883;
  --teal: #5EEAD4;
  --teal-dim: #1E3A38;
  --amber: #F5B942;
  --amber-dim: #3A2E14;
  --rose: #FB7185;
  --font-display: 'Space Mono', monospace;
  --font-body: 'Inter', sans-serif;
  --font-mono: 'JetBrains Mono', monospace;
  --radius: 10px;
}

* { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  line-height: 1.5;
}

a { color: inherit; }

.mono, .field-input, code { font-family: var(--font-mono); }

/* ---------- Header ---------- */
.site-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 40px;
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  background: rgba(10, 14, 22, 0.9);
  backdrop-filter: blur(8px);
  z-index: 20;
}

.brand {
  display: flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  font-family: var(--font-display);
}

.brand-mark {
  background: var(--teal);
  color: #06110F;
  font-weight: 700;
  padding: 3px 7px;
  border-radius: 4px;
  font-size: 13px;
  letter-spacing: 0.05em;
}

.brand-name {
  color: var(--text);
  font-size: 16px;
  letter-spacing: 0.02em;
}

.site-nav {
  display: flex;
  gap: 28px;
}

.site-nav a {
  text-decoration: none;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 13px;
  letter-spacing: 0.06em;
  transition: color 0.15s ease;
}

.site-nav a:hover { color: var(--teal); }

/* ---------- Footer ---------- */
.site-footer {
  border-top: 1px solid var(--border);
  padding: 28px 40px 40px;
  text-align: center;
  font-size: 13px;
  color: var(--muted-2);
}

.site-footer p { margin: 4px 0; }
.muted { color: var(--muted-2); }

/* ---------- Hero ---------- */
.hero {
  position: relative;
  padding: 90px 40px 70px;
  overflow: hidden;
  border-bottom: 1px solid var(--border);
}

.hero-bits {
  position: absolute;
  inset: 0;
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--teal);
  opacity: 0.06;
  line-height: 1.6;
  white-space: pre-wrap;
  overflow: hidden;
  pointer-events: none;
  user-select: none;
}

.hero-inner {
  max-width: 720px;
  position: relative;
}

.eyebrow {
  font-family: var(--font-mono);
  color: var(--teal);
  font-size: 13px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  margin: 0 0 18px;
}

.hero h1 {
  font-family: var(--font-display);
  font-size: 46px;
  line-height: 1.15;
  margin: 0 0 22px;
  font-weight: 700;
  letter-spacing: -0.01em;
}

.hero-sub {
  color: var(--muted);
  font-size: 16px;
  max-width: 600px;
  margin: 0;
}

.back-link {
  text-decoration: none;
  font-size: 13px;
}
.back-link:hover { color: var(--teal); }

/* ---------- Module grid (landing) ---------- */
.module-grid {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--border);
  border: 1px solid var(--border);
  margin: 0;
}

.module-card {
  background: var(--surface);
  padding: 34px;
  text-decoration: none;
  color: var(--text);
  display: flex;
  flex-direction: column;
  gap: 12px;
  transition: background 0.15s ease;
}

.module-card:hover {
  background: var(--surface-2);
}

.module-card-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.module-badge {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--bg);
  background: var(--teal);
  padding: 3px 8px;
  border-radius: 4px;
  letter-spacing: 0.04em;
  margin-left: 12px;
}

.module-code {
  font-family: var(--font-mono);
  color: var(--muted-2);
  font-size: 12px;
  letter-spacing: 0.08em;
}

.module-card h2 {
  font-family: var(--font-display);
  font-size: 22px;
  margin: 0;
}

.module-card p {
  color: var(--muted);
  font-size: 14px;
  margin: 0;
  flex-grow: 1;
}

.module-card-foot {
  display: flex;
  justify-content: space-between;
  font-size: 12px;
  color: var(--muted-2);
  font-family: var(--font-mono);
  padding-top: 8px;
  border-top: 1px solid var(--border);
}

.module-card .arrow {
  color: var(--teal);
}

/* ---------- How it works ---------- */
.how-it-works {
  padding: 70px 40px;
  max-width: 1100px;
  margin: 0 auto;
}

.how-it-works h2 {
  font-family: var(--font-display);
  font-size: 24px;
  margin-bottom: 34px;
}

.steps-row {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 24px;
}

.how-step {
  border-left: 2px solid var(--teal);
  padding-left: 18px;
}

.how-num {
  font-family: var(--font-mono);
  color: var(--teal);
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

.how-step p {
  color: var(--muted);
  font-size: 14px;
  margin: 8px 0 0;
}

/* ---------- Module header ---------- */
.module-header {
  padding: 50px 40px 30px;
  max-width: 1100px;
  margin: 0 auto;
}

.module-header h1 {
  font-family: var(--font-display);
  font-size: 32px;
  margin: 0 0 14px;
  display: flex;
  align-items: center;
  gap: 14px;
}

/* ---------- Workbench ---------- */
.workbench {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 40px 40px;
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 26px;
}

.panel-title {
  font-family: var(--font-mono);
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted-2);
  margin-bottom: 18px;
}

.mode-toggle {
  display: flex;
  background: var(--surface-2);
  border-radius: 8px;
  padding: 4px;
  margin-bottom: 22px;
}

.mode-btn {
  flex: 1;
  background: transparent;
  border: none;
  color: var(--muted);
  font-family: var(--font-mono);
  font-size: 13px;
  padding: 9px 0;
  border-radius: 6px;
  cursor: pointer;
  transition: all 0.15s ease;
}

.mode-btn.active {
  background: var(--teal);
  color: #06110F;
  font-weight: 600;
}

.mode-btn[data-mode="decrypt"].active {
  background: var(--amber);
  color: #2A1E05;
}

.field-label {
  display: block;
  font-size: 13px;
  color: var(--muted);
  margin: 16px 0 8px;
}

.field-input {
  width: 100%;
  background: var(--surface-2);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 12px 14px;
  border-radius: 8px;
  font-size: 15px;
  letter-spacing: 0.03em;
  outline: none;
  transition: border-color 0.15s ease;
}

.field-input:focus {
  border-color: var(--teal);
}

.field-hint {
  display: block;
  font-size: 12px;
  color: var(--muted-2);
  margin-top: 4px;
  min-height: 16px;
}

.field-hint.error { color: var(--rose); }

.btn-row {
  display: flex;
  gap: 10px;
  margin-top: 22px;
  flex-wrap: wrap;
}

.btn {
  font-family: var(--font-mono);
  font-size: 13px;
  padding: 11px 18px;
  border-radius: 8px;
  border: 1px solid var(--border);
  cursor: pointer;
  background: transparent;
  color: var(--text);
  transition: all 0.15s ease;
}

.btn:focus-visible {
  outline: 2px solid var(--teal);
  outline-offset: 2px;
}

.btn-primary {
  background: var(--teal);
  color: #06110F;
  border-color: var(--teal);
  font-weight: 600;
}

.btn-primary:hover { filter: brightness(1.08); }

.btn-ghost:hover { border-color: var(--muted-2); }

.btn-outline {
  border-color: var(--teal);
  color: var(--teal);
  width: 100%;
}

.btn-outline:hover { background: var(--teal-dim); }

.btn:disabled {
  opacity: 0.4;
  cursor: not-allowed;
}

.form-error {
  margin-top: 16px;
  background: rgba(251, 113, 133, 0.1);
  border: 1px solid var(--rose);
  color: var(--rose);
  padding: 10px 14px;
  border-radius: 8px;
  font-size: 13px;
}

/* ---------- Result panel ---------- */
.result-panel {
  display: flex;
  flex-direction: column;
}

.result-empty {
  color: var(--muted-2);
  font-size: 14px;
  margin: auto 0;
  text-align: center;
  padding: 40px 0;
}

.result-label {
  font-family: var(--font-mono);
  font-size: 12px;
  color: var(--teal);
  text-transform: uppercase;
  letter-spacing: 0.08em;
}

.result-hex {
  margin-top: 14px;
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--muted);
}

/* ---------- Bit boxes (signature element) ---------- */
.bit-row {
  display: flex;
  flex-wrap: wrap;
  gap: 6px;
  margin-top: 10px;
}

.bit-box {
  width: 30px;
  height: 34px;
  display: flex;
  align-items: center;
  justify-content: center;
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 5px;
  font-family: var(--font-mono);
  font-size: 14px;
  color: var(--muted);
  animation: bitFlip 0.35s ease both;
}

.bit-box.on {
  background: var(--teal-dim);
  border-color: var(--teal);
  color: var(--teal);
}

.bit-row-lg .bit-box {
  width: 36px;
  height: 40px;
  font-size: 16px;
}

.bit-box.grp-start { margin-left: 10px; }
.bit-box.grp-start:first-child { margin-left: 0; }

@keyframes bitFlip {
  from { transform: rotateX(90deg); opacity: 0; }
  to { transform: rotateX(0deg); opacity: 1; }
}

/* ---------- Solution / steps ---------- */
.solution-section {
  max-width: 1100px;
  margin: 0 auto;
  padding: 0 40px 80px;
}

.solution-steps {
  margin-top: 20px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.step-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
}

.step-title {
  font-family: var(--font-mono);
  font-size: 13px;
  color: var(--amber);
  margin: 0 0 14px;
  letter-spacing: 0.02em;
}

.step-field {
  margin-bottom: 12px;
}

.step-field:last-child { margin-bottom: 0; }

.step-field-label {
  font-size: 12px;
  color: var(--muted);
  margin-bottom: 4px;
}

.step-table {
  width: 100%;
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 13px;
}

.step-table th, .step-table td {
  border: 1px solid var(--border);
  padding: 7px 10px;
  text-align: center;
}

.step-table th {
  background: var(--surface-2);
  color: var(--muted);
  font-weight: 500;
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

.step-matrix-wrap {
  display: flex;
  gap: 20px;
  flex-wrap: wrap;
}

.step-matrix {
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 14px;
}

.step-matrix td {
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--teal);
  width: 36px;
  height: 34px;
  text-align: center;
}

.step-text {
  font-size: 14px;
  color: var(--muted);
  margin: 0;
}

.step-kv {
  display: flex;
  gap: 24px;
  flex-wrap: wrap;
}

.step-kv-item .step-field-label { margin-bottom: 4px; }
.step-kv-item .step-kv-value {
  font-family: var(--font-mono);
  color: var(--teal);
  font-size: 15px;
}

.step-note {
  font-size: 12px;
  color: var(--muted-2);
  margin-top: 4px;
}

/* ---------- Responsive ---------- */
@media (max-width: 860px) {
  .site-header { padding: 16px 20px; }
  .site-nav { gap: 16px; }
  .hero { padding: 60px 20px 50px; }
  .hero h1 { font-size: 32px; }
  .module-grid { grid-template-columns: 1fr; }
  .steps-row { grid-template-columns: 1fr; }
  .workbench { grid-template-columns: 1fr; padding: 0 20px 30px; }
  .module-header { padding: 34px 20px 20px; }
  .solution-section { padding: 0 20px 60px; }
  .how-it-works { padding: 50px 20px; }
}