:root{
  --ink:#14274E; --ink-soft:#48546E; --paper:#F6F8FB; --paper-card:#FFFFFF;
  --rule:#DCE3EC; --rule-strong:#B7C3D6; --tick:#2C5697; --tick-soft:#E7EEF7;
  --amber:#C9A227; --amber-ink:#4A3900; --pen-red:#A33B33;
  --amber-soft:#F6EFD8; --pen-red-soft:#F5E3E1;
  --shadow: 0 18px 40px -18px rgba(20,39,78,0.28);
}
*{box-sizing:border-box;}
body{margin:0; background:var(--paper); color:var(--ink); font-family:'IBM Plex Sans',sans-serif; -webkit-font-smoothing:antialiased;}
h1,h2,h3{font-family:'IBM Plex Serif',serif; margin:0; line-height:1.15; letter-spacing:-0.01em;}
a{color:inherit; text-decoration:none;}
.mono{font-family:'IBM Plex Mono',monospace;}
.wrap{max-width:1372px; margin:0 auto; padding:0 32px;}

.rebuild-banner{background:var(--ink); color:var(--paper); overflow:hidden; white-space:nowrap; border-bottom:1px solid rgba(255,255,255,0.12);}
.rebuild-banner .track{display:flex; width:max-content; animation:rebuildScroll 22s linear infinite;}
.rebuild-banner .track span{display:inline-block; padding:12px 40px; font-family:'IBM Plex Mono',monospace; font-size:18px; font-weight:600; letter-spacing:.03em; white-space:nowrap; color:var(--paper);}
@keyframes rebuildScroll{0%{transform:translateX(0);}100%{transform:translateX(-50%);}}

.hero-window-note{display:flex; align-items:center; gap:9px; background:var(--ink); color:var(--paper); border-radius:8px 8px 6px 6px; padding:10px 16px; margin-bottom:18px; box-shadow:0 10px 24px -14px rgba(20,39,78,0.45);}
.hero-window-note .wdot{width:8px; height:8px; border-radius:50%; flex-shrink:0;}
.hero-window-note .wdot-red{background:#B23A2E;}
.hero-window-note .wdot-amber{background:#F2AE00;}
.hero-window-note .wdot-green{background:#1F7A4D;}
.hero-window-note .hero-window-text{font-family:'IBM Plex Mono',monospace; font-size:13.5px; font-weight:600; letter-spacing:.01em; color:var(--paper); margin-left:4px; line-height:1.4;}

header.site{position:sticky; top:0; z-index:50; background:var(--ink); border-bottom:1px solid rgba(255,255,255,0.14);}
nav.wrap{display:flex; align-items:center; justify-content:space-between; height:76px;}
.logo{display:flex; align-items:center; gap:10px; font-family:'IBM Plex Serif',serif; font-weight:600; font-size:21px; color:var(--paper);}
.logo .mark{width:30px; height:30px; border-radius:3px; background:var(--paper); color:var(--ink); display:flex; align-items:center; justify-content:center; font-family:'IBM Plex Mono',monospace; font-size:15px; font-weight:600; transform:rotate(-4deg);}
.nav-links{display:flex; align-items:center; gap:26px; font-size:16.5px; font-weight:500; color:rgba(255,255,255,0.78);}
.nav-links a{position:relative; padding:4px 0;}
.nav-links a:hover{color:var(--paper);}
.nav-links a::after{content:""; position:absolute; left:0; right:100%; bottom:-2px; height:2px; background:var(--amber); transition:right .18s ease;}
.nav-links a:hover::after{right:0;}
.nav-cta{display:flex; align-items:center; gap:14px;}
.nav-cta .btn-outline{color:var(--paper); border-color:rgba(255,255,255,0.5);}
.nav-cta .btn-outline:hover{border-color:var(--paper);}
.nav-cta .btn-primary{background:var(--paper); color:var(--ink);}
.nav-cta .mono{color:rgba(255,255,255,0.78) !important;}

.nav-toggle{display:none; flex-direction:column; justify-content:center; align-items:center; gap:5px; width:38px; height:38px; border:1px solid rgba(255,255,255,0.4); border-radius:3px; background:var(--paper); cursor:pointer; padding:0; flex-shrink:0;}
.nav-toggle span{display:block; width:18px; height:2px; background:var(--ink); border-radius:1px; transition:transform .22s ease, opacity .22s ease;}
.nav-toggle.is-active span:nth-child(1){transform:translateY(7px) rotate(45deg);}
.nav-toggle.is-active span:nth-child(2){opacity:0;}
.nav-toggle.is-active span:nth-child(3){transform:translateY(-7px) rotate(-45deg);}

.mobile-nav{display:none; flex-direction:column; max-height:0; overflow:hidden; background:var(--paper-card); border-top:1px solid var(--rule); transition:max-height .28s ease;}
.mobile-nav.open{max-height:520px;}
.mobile-nav a{padding:15px 32px; font-size:17px; font-weight:500; color:var(--ink); border-bottom:1px solid var(--rule);}
.mobile-nav a:active{background:var(--tick-soft);}
.mobile-nav-cta{padding:18px 32px 24px; display:flex; flex-direction:column; gap:12px;}

.btn{display:inline-flex; align-items:center; gap:8px; padding:11px 20px; border-radius:2px; font-weight:600; font-size:16.5px; cursor:pointer; border:1.5px solid transparent; transition:transform .18s ease, box-shadow .18s ease;}
.btn-primary{background:var(--ink); color:var(--paper);}
.btn-primary:hover{transform:translateY(-2px); box-shadow:var(--shadow);}
.btn-amber{background:var(--amber); color:var(--amber-ink);}
.btn-outline{background:transparent; color:var(--ink); border-color:var(--ink-soft);}
.btn-outline:hover{border-color:var(--ink);}
.btn-block{width:100%; justify-content:center;}

main{min-height:60vh;}
.page-head{padding:56px 0 40px; border-bottom:1px solid var(--rule); background:var(--paper-card);}
.eyebrow{font-family:'IBM Plex Mono',monospace; font-size:14px; font-weight:600; letter-spacing:.08em; color:var(--tick); margin-bottom:12px;}
.page-head h1{font-size:clamp(32px,4vw,46px);}
.page-head p{margin-top:12px; color:var(--ink-soft); font-size:18px; max-width:60ch;}

.hero-grid{display:grid; grid-template-columns:1.05fr .95fr; gap:48px; align-items:center;}
.hero-visual{position:relative; display:flex; justify-content:center;}
.hero-mock{width:100%; max-width:380px; background:var(--paper); border:1px solid var(--rule); border-radius:10px; box-shadow:0 30px 60px -24px rgba(23,32,51,0.32); transform:rotate(1.4deg); overflow:hidden;}
.hero-mock .mock-bar{display:flex; align-items:center; gap:6px; padding:11px 14px; background:var(--ink); border-bottom:1px solid rgba(255,255,255,0.08);}
.hero-mock .mock-bar span{width:8px; height:8px; border-radius:50%; background:rgba(244,246,245,0.35);}
.hero-mock .mock-bar span:nth-child(1){background:#B23A2E;}
.hero-mock .mock-bar span:nth-child(2){background:#F2AE00;}
.hero-mock .mock-bar span:nth-child(3){background:#1F7A4D;}
.hero-mock .mock-body{padding:20px;}
.hero-mock .mock-head{display:flex; justify-content:space-between; font-family:'IBM Plex Mono',monospace; font-size:12.5px; color:var(--ink-soft); margin-bottom:10px;}
.hero-mock .mock-q{font-family:'IBM Plex Serif',serif; font-style:italic; font-size:16.5px; color:var(--ink); line-height:1.5; margin-bottom:14px;}
.hero-mock .mock-line{height:9px; border-radius:2px; background:var(--rule); margin-bottom:8px;}
.hero-mock .mock-line.short{width:62%;}
.hero-mock .mock-solve{display:inline-flex; align-items:center; gap:6px; font-size:14.5px; font-weight:600; color:var(--tick); margin-top:6px;}
.hero-mock .mock-badge{position:absolute; top:-14px; right:18px; background:var(--amber); color:var(--amber-ink); font-family:'IBM Plex Mono',monospace; font-size:13px; font-weight:700; padding:7px 12px; border-radius:20px; box-shadow:0 8px 18px -8px rgba(242,174,0,0.6); transform:rotate(-3deg);}
section{padding:60px 0;}
.section-label{font-family:'IBM Plex Mono',monospace; font-size:14px; font-weight:600; color:var(--ink-soft); letter-spacing:.08em; text-transform:uppercase; margin-bottom:12px; display:block;}

.trust-strip{background:var(--tick-soft); color:var(--ink);}
.trust-row{display:grid; grid-template-columns:repeat(3,1fr);}
.trust-item{padding:4px 18px; text-align:center; border-right:1px solid var(--rule-strong);}
.trust-item:last-child{border-right:none;}
.trust-item .num{font-family:'IBM Plex Mono',monospace; font-weight:600; font-size:24px; color:var(--ink); white-space:nowrap;}
.trust-item .label{margin-top:4px; font-size:15.5px; color:var(--ink-soft); letter-spacing:.02em; max-width:26ch; margin-left:auto; margin-right:auto;}

.info-grid .tile{cursor:default; padding:26px 22px 24px; background:var(--tick-soft); border:none;}
.info-grid .tile.accent-amber{background:var(--amber-soft);}
.info-grid .tile.accent-red{background:var(--pen-red-soft);}
.info-grid .tile:hover{transform:none; box-shadow:none; border-color:transparent;}
.info-grid .tile .icon{width:26px; height:26px; color:var(--tick); margin-bottom:16px; display:block;}
.info-grid .tile.accent-amber .icon{color:var(--amber-ink);}
.info-grid .tile.accent-red .icon{color:var(--pen-red);}
.info-grid .tile h3{font-size:18.5px; white-space:nowrap; overflow:hidden; text-overflow:ellipsis;}

.problem-grid{display:grid; grid-template-columns:0.95fr 1.05fr; gap:56px; align-items:start;}
.problem-grid h2{font-size:clamp(28px,3.2vw,36px); max-width:11ch;}
.problem-grid .body p{font-size:18.5px; line-height:1.75; color:var(--ink-soft); max-width:54ch;}
.problem-grid .body p strong{color:var(--ink); font-weight:600;}
.problem-grid .body p + p{margin-top:16px;}

.card-grid{display:grid; grid-template-columns:repeat(3,1fr); gap:20px;}
.card-grid-4{grid-template-columns:repeat(4,1fr);}
.tile{position:relative; background:var(--paper-card); border:1px solid var(--rule); border-radius:6px; padding:28px 24px 26px; box-shadow:0 1px 2px rgba(23,32,51,0.05); transition:transform .2s ease, box-shadow .2s ease, border-color .2s ease; overflow:hidden;}
.tile::before{content:""; position:absolute; top:0; left:0; right:0; height:3px; background:var(--tick); opacity:.85;}
.tile.accent-amber::before{background:var(--amber);}
.tile.accent-red::before{background:var(--pen-red);}
.tile:hover{transform:translateY(-4px); box-shadow:var(--shadow); border-color:var(--rule-strong);}
.tile .tag{display:inline-flex; align-items:center; gap:6px; font-family:'IBM Plex Mono',monospace; font-size:13px; font-weight:600; color:var(--tick); background:var(--tick-soft); padding:4px 9px; border-radius:2px; margin-bottom:14px;}
.tile .tag svg{width:12px; height:12px; flex-shrink:0;}
.tile.disabled{opacity:.55;}
.tile.disabled::before{background:var(--rule-strong);}
.tile.disabled .tag{background:var(--rule); color:var(--ink-soft);}
.tile h3{font-size:20px; margin-bottom:7px;}
.tile p{color:var(--ink-soft); font-size:16px; line-height:1.55;}
.tile:focus-visible, .btn:focus-visible, a:focus-visible{outline:2px solid var(--tick); outline-offset:2px;}

.topic-row{display:flex; align-items:center; justify-content:space-between; padding:18px 22px; background:var(--paper-card); border:1px solid var(--rule); border-radius:3px; margin-bottom:12px;}
.topic-row .name{font-weight:600; font-size:17.5px;}
.topic-row .meta{font-size:14.5px; color:var(--ink-soft); margin-top:3px;}
.lock-badge{font-family:'IBM Plex Mono',monospace; font-size:13px; font-weight:600; padding:4px 9px; border-radius:20px;}
.lock-badge.free{color:var(--tick); background:var(--tick-soft);}
.lock-badge.locked{color:var(--pen-red); border:1px solid var(--pen-red);}

.locked-banner{background:var(--ink); color:var(--paper); border-radius:4px; padding:32px 28px; text-align:center; margin:24px 0;}
.locked-banner h3{color:var(--paper); font-size:24px; margin-bottom:10px;}
.locked-banner p{color:rgba(244,246,245,0.75); margin-bottom:20px;}

.qcard{background:var(--paper-card); border:1px solid var(--rule); border-radius:4px; padding:24px; margin-bottom:18px;}
.qcard .qhead{display:flex; justify-content:space-between; font-family:'IBM Plex Mono',monospace; font-size:14px; color:var(--ink-soft); margin-bottom:12px;}
.qcard .qtext{font-family:'Inter','IBM Plex Sans',-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif; font-style:normal; font-size:18px; margin-bottom:14px; white-space:pre-line;}
.qcard details summary{cursor:pointer; font-weight:600; color:var(--tick); font-size:16px;}
.qcard details .sol{margin-top:12px; padding-top:12px; border-top:1px dashed var(--rule-strong); font-size:16.5px; color:var(--ink-soft); line-height:1.6; white-space:pre-line;}
mjx-container{font-style:normal !important;}
.qtext, .qtext *:not(mjx-container):not(mjx-container *),
.sol, .sol *:not(mjx-container):not(mjx-container *) {
  font-family:'Inter','IBM Plex Sans',-apple-system,BlinkMacSystemFont,'Segoe UI',Roboto,sans-serif !important;
  font-style:normal !important;
}
.qtext table, .sol table{border-collapse:collapse; margin:12px 0; font-style:normal; width:auto; white-space:normal;}
.qtext table th, .sol table th{background:var(--ink); color:var(--paper); padding:8px 14px; font-family:'IBM Plex Mono',monospace; font-size:14px; text-transform:uppercase; letter-spacing:.03em;}
.qtext table td, .sol table td{padding:8px 14px; border:1px solid var(--rule); font-size:16px; white-space:normal;}
.qtext table tr:nth-child(even) td, .sol table tr:nth-child(even) td{background:var(--paper-card);}

.auth-box{max-width:420px; margin:60px auto; background:var(--paper-card); border:1px solid var(--rule); border-radius:4px; padding:36px 32px;}
.auth-box h1{font-size:28px; margin-bottom:6px;}
.auth-box p.sub{color:var(--ink-soft); font-size:16.5px; margin-bottom:24px;}
.field{margin-bottom:18px;}
.field label{display:block; font-size:15px; font-weight:600; margin-bottom:6px;}
.field input{width:100%; padding:11px 12px; border:1px solid var(--rule-strong); border-radius:3px; font-size:17px; font-family:inherit;}
.field input:focus{outline:none; border-color:var(--tick);}
.alert{padding:12px 14px; border-radius:3px; font-size:16px; margin-bottom:18px;}
.alert.error{background:#FBEAE8; color:var(--pen-red); border:1px solid rgba(178,58,46,0.3);}
.alert.success{background:var(--tick-soft); color:var(--tick); border:1px solid rgba(31,122,77,0.3);}
.auth-switch{margin-top:18px; font-size:16px; text-align:center; color:var(--ink-soft);}
.auth-switch a{color:var(--tick); font-weight:600;}

.pricing-grid{display:grid; grid-template-columns:repeat(2,1fr); gap:24px; max-width:820px; margin:0 auto;}
.plan-card{background:var(--paper-card); border:1px solid var(--rule-strong); border-radius:4px; overflow:hidden;}
.plan-card .top{padding:26px 26px 18px;}
.plan-card .name{font-family:'IBM Plex Mono',monospace; font-size:14px; letter-spacing:.06em; text-transform:uppercase; color:var(--ink-soft);}
.plan-card .price{font-family:'IBM Plex Serif',serif; font-size:30px; font-weight:600; margin-top:6px;}
.plan-card .price span{font-family:'IBM Plex Sans',sans-serif; font-size:15px; font-weight:400; color:var(--ink-soft);}
.plan-card .annual-note{margin-top:8px; font-size:14.5px; color:var(--tick);}
.plan-card ul{list-style:none; margin:16px 0; padding:0 26px;}
.plan-card li{font-size:15.5px; color:var(--ink-soft); padding-left:20px; position:relative; margin-bottom:9px;}
.plan-card li::before{content:"✓"; position:absolute; left:0; color:var(--tick); font-weight:600;}
.plan-card .bottom{padding:0 26px 26px;}

table.plain{width:100%; border-collapse:collapse; margin:20px 0;}
table.plain th, table.plain td{text-align:left; padding:10px 12px; border-bottom:1px solid var(--rule); font-size:16.5px;}
table.plain th{font-family:'IBM Plex Mono',monospace; font-size:13.5px; text-transform:uppercase; color:var(--ink-soft);}

.faq-item{border-bottom:1px solid var(--rule); padding:18px 0;}
.faq-item summary{cursor:pointer; font-weight:600; font-size:17.5px;}
.faq-item .a{margin-top:10px; color:var(--ink-soft); font-size:16.5px; line-height:1.6;}

footer.site{background:var(--paper-card); border-top:1px solid var(--rule); padding:56px 0 28px; margin-top:60px;}
.foot-grid{display:grid; grid-template-columns:1.4fr 1fr 1fr 1fr; gap:36px; margin-bottom:44px;}
.foot-brand .logo{margin-bottom:14px;}
.foot-brand p{font-size:15.5px; color:var(--ink-soft); line-height:1.6; max-width:32ch;}
.foot-col h4{font-family:'IBM Plex Mono',monospace; font-size:14px; letter-spacing:.06em; text-transform:uppercase; color:var(--ink-soft); margin-bottom:14px;}
.foot-col a{display:block; font-size:16px; color:var(--ink); margin-bottom:10px; opacity:.85;}
.foot-col a:hover{opacity:1; color:var(--tick);}
.foot-bottom{border-top:1px solid var(--rule); padding-top:22px; display:flex; justify-content:space-between; flex-wrap:wrap; gap:16px; font-size:14.5px; color:var(--ink-soft);}
.foot-bottom .copy{white-space:nowrap;}
.disclaimer{max-width:680px; line-height:1.6; opacity:.85;}

.subject-groups{display:grid; grid-template-columns:repeat(3,1fr); gap:22px; align-items:start;}
.subject-group{background:var(--paper-card); border:1px solid var(--rule); border-radius:8px; padding:26px 24px 22px; box-shadow:0 1px 2px rgba(23,32,51,0.05); transition:box-shadow .2s ease, border-color .2s ease;}
.subject-group:hover{box-shadow:var(--shadow); border-color:var(--rule-strong);}
.subject-group-head{display:flex; align-items:center; gap:11px; margin-bottom:18px;}
.subject-group-icon{width:34px; height:34px; border-radius:7px; background:var(--tick-soft); color:var(--tick); display:flex; align-items:center; justify-content:center; flex-shrink:0;}
.subject-group-icon svg{width:18px; height:18px;}
.subject-group-head h3{font-size:19.5px;}
.level-grid{display:grid; grid-template-columns:1fr 1fr; gap:10px;}
.level-grid.level-grid-1{grid-template-columns:1fr;}
.level-pill{display:flex; align-items:center; justify-content:space-between; gap:8px; padding:11px 13px; background:var(--paper); border:1px solid var(--rule); border-radius:5px; transition:transform .15s ease, border-color .15s ease, background-color .15s ease;}
.level-pill:hover{border-color:var(--tick); background:var(--tick-soft); transform:translateY(-1px);}
.level-pill .level-name{font-weight:600; font-size:15px; color:var(--ink);}
.level-pill .tag{margin-bottom:0; font-family:'IBM Plex Mono',monospace; font-size:10.5px; font-weight:600; color:var(--tick); background:var(--paper-card); padding:3px 7px; border-radius:2px; letter-spacing:.03em; flex-shrink:0;}
.level-pill:hover .tag{background:var(--paper);}
.subject-group-note{margin-top:16px; font-size:14px; color:var(--ink-soft);}

@media (max-width:900px){
  .card-grid, .card-grid-4{grid-template-columns:1fr 1fr;}
  .subject-groups{grid-template-columns:1fr 1fr;}
  .pricing-grid{grid-template-columns:1fr;}
  .problem-grid{grid-template-columns:1fr; gap:26px;}
  .foot-grid{grid-template-columns:1fr 1fr; gap:28px;}
}
@media (max-width:640px){
  .nav-links{display:none;}
  .nav-cta{display:none;}
  .nav-toggle{display:flex;}
  .mobile-nav{display:flex;}
  .card-grid, .card-grid-4{grid-template-columns:1fr;}
  .subject-groups{grid-template-columns:1fr;}
  .hero-grid{grid-template-columns:1fr !important;}
  .hero-visual{margin-top:32px;}
  .trust-row{grid-template-columns:1fr;}
  .trust-item{border-right:none; border-bottom:1px solid var(--rule-strong);}
  .trust-item:last-child{border-bottom:none;}
  .foot-grid{grid-template-columns:1fr; gap:30px;}
}