/* ============================================================
   CipherLab — Design tokens
   ============================================================ */
:root{
  --bg:            #0A0E14;
  --bg-alt:        #0F141C;
  --surface:       #131A24;
  --surface-2:     #1A2230;
  --border:        #232D3D;
  --border-soft:   #1C2530;
  --text:          #E7ECF3;
  --text-muted:    #8A93A6;
  --text-dim:      #5B6577;
  --accent:        #5EEAD4;   /* cyan - primary signal   */
  --accent-dim:    #2C7A70;
  --accent-2:      #F5A524;   /* amber - XOR / key ops   */
  --accent-3:      #F97066;   /* red   - errors / delete */
  --accent-4:      #7C9CFF;   /* blue  - permutation ops */
  --radius:        10px;
  --radius-sm:     6px;
  --mono: 'JetBrains Mono', ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  --sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --disp: 'Space Grotesk', var(--sans);
}

*{ box-sizing:border-box; margin:0; padding:0; }

html{ scroll-behavior:smooth; }

body{
  background:var(--bg);
  color:var(--text);
  font-family:var(--sans);
  line-height:1.55;
  min-height:100vh;
  background-image:
    radial-gradient(circle at 15% 0%, rgba(94,234,212,0.06), transparent 40%),
    radial-gradient(circle at 85% 20%, rgba(124,156,255,0.05), transparent 45%);
  background-attachment:fixed;
}

a{ color:inherit; text-decoration:none; }

::selection{ background:var(--accent); color:#04110E; }

/* ---- Layout shells --------------------------------------- */
.wrap{ max-width:1120px; margin:0 auto; padding:0 24px; }

header.site{
  position:sticky; top:0; z-index:50;
  background:rgba(10,14,20,0.85);
  backdrop-filter:blur(10px);
  border-bottom:1px solid var(--border-soft);
}
header.site .bar{
  display:flex; align-items:center; justify-content:space-between;
  padding:16px 24px; max-width:1120px; margin:0 auto;
}
.brand{ display:flex; align-items:center; gap:10px; font-family:var(--disp); font-weight:600; font-size:1.05rem; letter-spacing:0.01em; }
.brand .dot{
  width:10px; height:10px; border-radius:2px; background:var(--accent);
  box-shadow:0 0 12px rgba(94,234,212,0.8);
  animation:blink 2.4s ease-in-out infinite;
}
@keyframes blink{ 0%,100%{opacity:1;} 50%{opacity:0.25;} }

nav.top a{
  color:var(--text-muted); font-size:0.88rem; margin-left:22px; font-family:var(--mono);
  transition:color .15s;
}
nav.top a:hover{ color:var(--accent); }
nav.top a.active{ color:var(--accent); }

/* ---- Typography -------------------------------------------*/
h1,h2,h3{ font-family:var(--disp); font-weight:600; letter-spacing:-0.01em; }
.eyebrow{
  font-family:var(--mono); text-transform:uppercase; letter-spacing:0.14em;
  font-size:0.72rem; color:var(--accent); display:flex; align-items:center; gap:8px;
}
.eyebrow::before{ content:''; width:16px; height:1px; background:var(--accent); display:inline-block; }

p.lead{ color:var(--text-muted); font-size:1.05rem; max-width:60ch; }

/* ---- Buttons -------------------------------------------- */
.btn{
  display:inline-flex; align-items:center; gap:8px;
  font-family:var(--mono); font-size:0.85rem; font-weight:500;
  padding:11px 20px; border-radius:var(--radius-sm);
  border:1px solid var(--border); background:var(--surface);
  color:var(--text); cursor:pointer; transition:all .15s;
}
.btn:hover{ border-color:var(--accent); color:var(--accent); transform:translateY(-1px); }
.btn.primary{ background:var(--accent); color:#04110E; border-color:var(--accent); font-weight:600; }
.btn.primary:hover{ background:#7ff2e0; color:#04110E; }
.btn.ghost{ background:transparent; }
.btn.danger:hover{ border-color:var(--accent-3); color:var(--accent-3); }
.btn:disabled{ opacity:0.4; cursor:not-allowed; transform:none; }
.btn:focus-visible, a:focus-visible, input:focus-visible, select:focus-visible, button:focus-visible{
  outline:2px solid var(--accent); outline-offset:2px;
}

/* ---- Cards / surfaces ------------------------------------*/
.card{
  background:var(--surface); border:1px solid var(--border);
  border-radius:var(--radius); padding:24px;
}
.card + .card{ margin-top:20px; }

/* ---- Landing hero ------------------------------------------*/
.hero{ padding:88px 0 64px; }
.hero-grid{ display:grid; grid-template-columns:1.1fr 0.9fr; gap:48px; align-items:center; }
.hero h1{ font-size:2.6rem; line-height:1.08; margin:14px 0 18px; }
.hero h1 .hl{ color:var(--accent); }

.bitfield{
  font-family:var(--mono); font-size:0.95rem; line-height:1.9;
  background:var(--bg-alt); border:1px solid var(--border); border-radius:var(--radius);
  padding:20px; color:var(--text-dim); overflow:hidden; position:relative;
}
.bitfield .row{ display:flex; gap:6px; flex-wrap:wrap; margin-bottom:4px; }
.bitfield .bit{
  display:inline-flex; align-items:center; justify-content:center;
  width:22px; height:22px; border-radius:4px; background:var(--surface-2);
  color:var(--text-muted); font-size:0.78rem; transition:all .5s;
}
.bitfield .bit.on{ background:rgba(94,234,212,0.14); color:var(--accent); }
.bitfield .cap{ font-size:0.72rem; color:var(--text-dim); margin-top:10px; }

/* ---- Module grid on landing --------------------------------*/
.modules{ padding:20px 0 90px; }
.section-head{ margin-bottom:34px; }
.section-head h2{ font-size:1.7rem; margin-top:8px; }

.mod-grid{ display:grid; grid-template-columns:repeat(4,1fr); gap:18px; }
@media (max-width:920px){ .mod-grid{ grid-template-columns:repeat(2,1fr); } .hero-grid{ grid-template-columns:1fr; } }
@media (max-width:560px){ .mod-grid{ grid-template-columns:1fr; } }

.mod-card{
  background:var(--surface); border:1px solid var(--border); border-radius:var(--radius);
  padding:24px 20px; position:relative; overflow:hidden; transition:all .18s;
  display:flex; flex-direction:column; gap:10px; min-height:190px;
}
.mod-card:hover{ border-color:var(--accent); transform:translateY(-3px); box-shadow:0 12px 30px rgba(0,0,0,0.35); }
.mod-card .tag{ font-family:var(--mono); font-size:0.7rem; color:var(--text-dim); letter-spacing:0.08em; }
.mod-card h3{ font-size:1.3rem; }
.mod-card p{ color:var(--text-muted); font-size:0.88rem; flex:1; }
.mod-card .meta{ font-family:var(--mono); font-size:0.72rem; color:var(--accent-4); display:flex; gap:14px; }
.mod-card .go{ font-family:var(--mono); font-size:0.8rem; color:var(--accent); }

.mod-card.c-des{ border-left:3px solid var(--accent-4); }
.mod-card.c-sdes{ border-left:3px solid var(--accent); }
.mod-card.c-aes{ border-left:3px solid var(--accent-2); }
.mod-card.c-saes{ border-left:3px solid var(--accent-3); }

/* ---- Footer -------------------------------------------------*/
footer.site{ border-top:1px solid var(--border-soft); padding:28px 0; }
footer.site .wrap{ display:flex; justify-content:space-between; align-items:center; flex-wrap:wrap; gap:10px; }
footer.site span{ color:var(--text-dim); font-family:var(--mono); font-size:0.78rem; }

/* ---- Module page layout -------------------------------------*/
.module-header{ padding:36px 0 8px; }
.module-header h1{ font-size:1.9rem; margin-top:10px; }
.module-header p.lead{ margin-top:8px; }
.badge{
  display:inline-block; font-family:var(--mono); font-size:0.7rem; padding:3px 9px;
  border-radius:20px; border:1px solid var(--border); color:var(--text-muted); margin-right:8px;
}

.panel{ padding:26px 0 70px; display:grid; grid-template-columns:380px 1fr; gap:22px; align-items:start; }
@media (max-width:920px){ .panel{ grid-template-columns:1fr; } }

.form-group{ margin-bottom:16px; }
.form-group label{
  display:block; font-family:var(--mono); font-size:0.78rem; color:var(--text-muted);
  margin-bottom:6px; letter-spacing:0.03em;
}
.form-group .hint{ font-size:0.72rem; color:var(--text-dim); margin-top:5px; }
input[type=text], select, textarea{
  width:100%; background:var(--bg-alt); border:1px solid var(--border); color:var(--text);
  font-family:var(--mono); font-size:0.92rem; padding:11px 12px; border-radius:var(--radius-sm);
}
input[type=text]:focus, select:focus{ border-color:var(--accent); }
input.err{ border-color:var(--accent-3); }
.err-msg{ color:var(--accent-3); font-size:0.72rem; margin-top:5px; font-family:var(--mono); display:none; }
.err-msg.show{ display:block; }

.mode-toggle{ display:flex; gap:8px; }
.mode-toggle button{
  flex:1; padding:10px; border-radius:var(--radius-sm); border:1px solid var(--border);
  background:var(--bg-alt); color:var(--text-muted); font-family:var(--mono); font-size:0.82rem; cursor:pointer;
  transition:all .15s;
}
.mode-toggle button.active{ background:rgba(94,234,212,0.1); border-color:var(--accent); color:var(--accent); }

.actions{ display:flex; gap:10px; margin-top:20px; }

/* ---- Result box ------------------------------------------- */
.result-box{
  background:var(--bg-alt); border:1px solid var(--border); border-radius:var(--radius);
  padding:20px; margin-bottom:20px;
}
.result-box .label{ font-family:var(--mono); font-size:0.72rem; color:var(--text-dim); text-transform:uppercase; letter-spacing:0.1em; margin-bottom:10px; }
.chip-row{ display:flex; flex-wrap:wrap; gap:6px; }
.chip{
  font-family:var(--mono); font-size:0.95rem; background:var(--surface-2); color:var(--accent);
  border:1px solid var(--border); border-radius:6px; padding:6px 9px; min-width:30px; text-align:center;
}
.chip.group-sep{ margin-right:10px; }
.result-hex{ font-family:var(--mono); font-size:1.3rem; color:var(--accent); letter-spacing:0.05em; word-break:break-all; margin-top:8px; }

/* ---- Steps / accordion -------------------------------------*/
.steps{ display:flex; flex-direction:column; gap:10px; }
.step{
  border:1px solid var(--border); border-radius:var(--radius); background:var(--surface); overflow:hidden;
}
.step-head{
  display:flex; align-items:center; justify-content:space-between; padding:14px 18px; cursor:pointer;
  user-select:none;
}
.step-head:hover{ background:var(--surface-2); }
.step-head .idx{
  font-family:var(--mono); font-size:0.72rem; color:var(--bg); background:var(--accent);
  border-radius:5px; padding:2px 7px; margin-right:10px; font-weight:700;
}
.step-title{ display:flex; align-items:center; font-family:var(--disp); font-size:0.95rem; }
.step-chevron{ color:var(--text-dim); transition:transform .18s; font-family:var(--mono); }
.step.open .step-chevron{ transform:rotate(90deg); }
.step-body{ display:none; padding:0 18px 18px; border-top:1px solid var(--border-soft); }
.step.open .step-body{ display:block; }
.step-body table{ width:100%; border-collapse:collapse; margin:10px 0; font-family:var(--mono); font-size:0.82rem; }
.step-body td, .step-body th{ border:1px solid var(--border); padding:6px 8px; text-align:center; }
.step-body th{ color:var(--text-muted); background:var(--bg-alt); font-weight:500; }
.step-body .row-label{ text-align:left; color:var(--text-muted); font-family:var(--mono); font-size:0.78rem; }
.step-note{ color:var(--text-muted); font-size:0.86rem; margin:8px 0; }
.calc-line{ font-family:var(--mono); font-size:0.86rem; color:var(--text); background:var(--bg-alt); border-radius:6px; padding:8px 10px; margin:4px 0; word-break:break-all; }
.calc-line .op{ color:var(--accent-2); }
.calc-line .arrow{ color:var(--text-dim); margin:0 6px; }
.calc-line .val{ color:var(--accent); }

.solution-toggle{ display:flex; align-items:center; justify-content:space-between; margin:26px 0 14px; }
.solution-toggle h2{ font-size:1.2rem; }

.state-grid{ display:inline-grid; gap:3px; font-family:var(--mono); }
.state-grid .cell{
  background:var(--surface-2); border:1px solid var(--border); border-radius:5px;
  min-width:42px; height:36px; display:flex; align-items:center; justify-content:center; color:var(--accent);
  font-size:0.8rem;
}

.grid4{ grid-template-columns:repeat(4,1fr); }
.grid2{ grid-template-columns:repeat(2,1fr); }

.hidden{ display:none !important; }

.empty-note{ color:var(--text-dim); font-family:var(--mono); font-size:0.85rem; padding:30px 0; text-align:center; border:1px dashed var(--border); border-radius:var(--radius); }

@media (prefers-reduced-motion: reduce){
  *{ animation:none !important; transition:none !important; }
}