/* ==========================================================
   S-AES Simulator — Design tokens
   Palette   : graphite/ink background, cipher-teal + signal-amber accents
   Type      : Space Grotesk (display) / Inter (body) / JetBrains Mono (data)
   Signature : the 2x2 nibble "state matrix" cell — every transformation
               is expressed as this same recurring visual unit.
   ========================================================== */

:root {
  --bg:            #0B0F14;
  --bg-alt:        #10151C;
  --surface:       #151B23;
  --surface-2:     #1B222C;
  --border:        #2A323D;
  --border-soft:   #212832;

  --text:          #E7ECF2;
  --text-dim:      #97A3B0;
  --text-faint:    #5C6774;

  --teal:          #4FE8C7;
  --teal-dim:      #2C8F7C;
  --amber:         #F2B84B;
  --amber-dim:     #8A6A2A;
  --danger:        #F0665E;

  --font-display:  'Space Grotesk', sans-serif;
  --font-body:     'Inter', sans-serif;
  --font-mono:     'JetBrains Mono', monospace;

  --radius: 6px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  line-height: 1.5;
  position: relative;
  min-height: 100vh;
}

/* faint circuit-grid backdrop, purely decorative */
.bg-grid {
  position: fixed;
  inset: 0;
  z-index: -1;
  background-image:
    linear-gradient(var(--border-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--border-soft) 1px, transparent 1px);
  background-size: 42px 42px;
  opacity: 0.35;
  mask-image: radial-gradient(ellipse 80% 60% at 50% 0%, black 40%, transparent 90%);
}

a { color: var(--teal); }

/* ---------------- Header ---------------- */
.site-header {
  padding: 2.5rem clamp(1rem, 4vw, 3rem) 1.5rem;
  border-bottom: 1px solid var(--border);
}

.brand { display: flex; align-items: center; gap: 1rem; }

.brand__mark {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  color: var(--teal);
  background: var(--surface);
  border: 1px solid var(--border);
  padding: 0.35rem 0.55rem;
  border-radius: var(--radius);
  letter-spacing: 0.15em;
}

.brand__text h1 {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 3vw, 2rem);
  margin: 0;
  font-weight: 700;
  letter-spacing: -0.01em;
}
.brand__text h1 span { color: var(--teal); font-weight: 500; }
.brand__text p {
  margin: 0.2rem 0 0;
  color: var(--text-dim);
  font-size: 0.85rem;
  font-family: var(--font-mono);
}

/* ---------------- Layout ---------------- */
.layout {
  max-width: 980px;
  margin: 0 auto;
  padding: 2.5rem clamp(1rem, 4vw, 3rem) 4rem;
  display: flex;
  flex-direction: column;
  gap: 1.75rem;
}

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 10px;
  padding: 1.75rem clamp(1rem, 3vw, 2rem);
}

.panel__title {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 600;
  margin: 0 0 1.25rem;
  display: flex;
  align-items: center;
  gap: 0.6rem;
  letter-spacing: 0.01em;
}

.panel__num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--bg);
  background: var(--teal);
  border-radius: 4px;
  padding: 0.15rem 0.45rem;
}

.hidden { display: none !important; }

/* ---------------- Form ---------------- */
.mode-switch {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.5rem;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 4px;
  width: max-content;
}
.mode-option {
  position: relative;
  cursor: pointer;
}
.mode-option input { position: absolute; opacity: 0; }
.mode-option span {
  display: block;
  padding: 0.45rem 1.1rem;
  border-radius: 4px;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-dim);
  transition: 0.15s ease;
}
.mode-option input:checked + span {
  background: var(--teal);
  color: var(--bg);
}

.field { margin-bottom: 1.1rem; }
.field label {
  display: block;
  font-size: 0.82rem;
  font-weight: 600;
  margin-bottom: 0.4rem;
  color: var(--text-dim);
}
.field input {
  width: 100%;
  background: var(--bg-alt);
  border: 1px solid var(--border);
  color: var(--text);
  font-family: var(--font-mono);
  font-size: 1rem;
  letter-spacing: 0.12em;
  padding: 0.7rem 0.85rem;
  border-radius: var(--radius);
  outline: none;
  transition: border-color 0.15s ease;
}
.field input:focus {
  border-color: var(--teal);
  box-shadow: 0 0 0 3px rgba(79, 232, 199, 0.15);
}
.field__hint {
  display: block;
  margin-top: 0.35rem;
  font-size: 0.75rem;
  color: var(--text-faint);
}

.error-box {
  background: rgba(240, 102, 94, 0.1);
  border: 1px solid var(--danger);
  color: #FFB4AF;
  padding: 0.7rem 0.9rem;
  border-radius: var(--radius);
  font-size: 0.85rem;
  margin-bottom: 1rem;
}

.btn-row { display: flex; gap: 0.75rem; margin-top: 1.4rem; }
.btn {
  font-family: var(--font-body);
  font-weight: 600;
  font-size: 0.88rem;
  padding: 0.65rem 1.4rem;
  border-radius: var(--radius);
  border: 1px solid transparent;
  cursor: pointer;
  transition: transform 0.1s ease, opacity 0.15s ease;
}
.btn:active { transform: scale(0.97); }
.btn--primary { background: var(--teal); color: var(--bg); }
.btn--primary:hover { opacity: 0.9; }
.btn--ghost { background: transparent; border-color: var(--border); color: var(--text-dim); }
.btn--ghost:hover { border-color: var(--text-faint); color: var(--text); }
.btn--outline {
  background: transparent;
  border-color: var(--border);
  color: var(--teal);
  width: 100%;
  margin-top: 1.25rem;
}
.btn--outline:hover { border-color: var(--teal); }

/* ---------------- Output ---------------- */
.output-caption {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--amber);
  margin: 0 0 0.75rem;
}
.output-display {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
}
@media (max-width: 560px) { .output-display { grid-template-columns: 1fr; } }

.output-display__item {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
}
.output-display__label {
  display: block;
  font-size: 0.72rem;
  color: var(--text-dim);
  margin-bottom: 0.35rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
}
.output-display__value {
  font-family: var(--font-mono);
  font-size: 1.25rem;
  color: var(--teal);
  letter-spacing: 0.08em;
  word-break: break-all;
}

/* ---------------- Steps ---------------- */
.steps-container {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.step-card {
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.1rem 1.2rem;
}
.step-card h4 {
  margin: 0 0 0.6rem;
  font-family: var(--font-display);
  font-size: 0.95rem;
  color: var(--text);
}
.step-note {
  font-size: 0.8rem;
  color: var(--text-dim);
  margin: 0.3rem 0 0.7rem;
}
.step-card--io { border-color: var(--teal-dim); }
.step-card--final { border-color: var(--amber); }

.ba-row {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
}
.ba-row--3 { justify-content: flex-start; }
.ba-arrow {
  font-family: var(--font-mono);
  color: var(--amber);
  font-size: 0.9rem;
  font-weight: 600;
}

/* ---- signature element: the 2x2 nibble state matrix ---- */
.state-block__title {
  font-size: 0.72rem;
  color: var(--text-faint);
  margin-bottom: 0.35rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.state-matrix {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 4px;
  width: max-content;
}
.nibble-cell {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: 4px;
  width: 64px;
  height: 52px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  font-family: var(--font-mono);
}
.nibble-cell--hl { border-color: var(--teal); }
.nibble-hex { font-size: 1.05rem; color: var(--teal); font-weight: 600; }
.nibble-bin { font-size: 0.62rem; color: var(--text-faint); margin-top: 2px; }

.word-grid {
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem;
  margin: 0.4rem 0 0.8rem;
}
.word-grid--keys { margin-top: 0.6rem; }
.word-chip {
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.45rem 0.7rem;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  display: flex;
  flex-direction: column;
  gap: 2px;
}
.word-chip__label { color: var(--text-faint); font-size: 0.68rem; text-transform: uppercase; letter-spacing: 0.06em; }
.word-chip__val { color: var(--teal); }
.word-chip__val em { color: var(--text-faint); font-style: normal; font-size: 0.68rem; margin-left: 0.3rem; }

hr { border: none; border-top: 1px dashed var(--border); margin: 0.8rem 0; }

/* GF trace */
.gf-col { margin-top: 0.5rem; font-size: 0.82rem; color: var(--text-dim); }
.gf-trace { margin: 0.4rem 0; }
.gf-trace summary {
  cursor: pointer;
  font-family: var(--font-mono);
  font-size: 0.78rem;
  color: var(--amber);
  padding: 0.3rem 0;
}
.gf-trace-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 0.4rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
}
.gf-trace-table th, .gf-trace-table td {
  border: 1px solid var(--border);
  padding: 0.35rem 0.5rem;
  text-align: center;
  color: var(--text-dim);
}
.gf-trace-table th { background: var(--surface-2); color: var(--text); }

/* ---------------- Reference tables ---------------- */
.ref-block { margin-bottom: 1.6rem; }
.ref-block h3 {
  font-family: var(--font-display);
  font-size: 0.9rem;
  margin: 0 0 0.6rem;
  color: var(--text);
}
.table-scroll { overflow-x: auto; }
.ref-table {
  border-collapse: collapse;
  font-family: var(--font-mono);
  font-size: 0.8rem;
  min-width: 100%;
}
.ref-table th, .ref-table td {
  border: 1px solid var(--border);
  padding: 0.45rem 0.65rem;
  text-align: center;
}
.ref-table th { background: var(--surface-2); color: var(--text-dim); font-weight: 500; }
.ref-table td { color: var(--teal); }

.ref-block--split {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.5rem;
}
@media (max-width: 640px) { .ref-block--split { grid-template-columns: 1fr; } }

.matrix-pre {
  font-family: var(--font-mono);
  background: var(--bg-alt);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.7rem 0.9rem;
  color: var(--teal);
  font-size: 0.85rem;
  margin: 0 0 0.9rem;
}
.ref-note { font-size: 0.78rem; color: var(--text-faint); }

/* ---------------- Footer ---------------- */
.site-footer {
  text-align: center;
  padding: 2rem 1rem 3rem;
  color: var(--text-faint);
  font-size: 0.78rem;
  font-family: var(--font-mono);
}

/* Focus visibility for accessibility */
button:focus-visible, input:focus-visible {
  outline: 2px solid var(--teal);
  outline-offset: 2px;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { transition: none !important; }
}