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/* Discrete mathematics additions */
:root{--green:#78dce0;--paper:#090d16;--card:#111a27;--soft:#172736}textarea{font:inherit}.hero-art{padding:24px;min-height:280px}.hero-art svg{max-height:280px}.hero h1{font-size:46px}.grid2{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}.topic-summary{border-top:1px solid var(--line);padding:18px 0}.topic-summary h3{margin:0 0 7px}.matrix{border-collapse:separate;border-spacing:5px;margin:16px 0}.matrix th{font-weight:500;font-size:12px;color:var(--muted)}.matrix button,.matrix td.bit{width:43px;height:42px;border:1px solid var(--line);border-radius:6px;background:#172331;text-align:center;font-family:monospace;font-size:17px}.matrix button.on{background:var(--green);color:#b5c5d5}.matrix td.added{background:#172331;border:2px solid #304055}.matrix button:hover{border-color:#304055}.status-grid{display:grid;grid-template-columns:repeat(3,1fr);gap:8px}.status-item{border:1px solid var(--line);border-radius:6px;padding:10px;font-size:12px}.status-item.yes{background:#172331}.status-item.no{background:#172331}.status-item span{display:block;font-size:10px;margin-top:5px}.lab-form{display:flex;gap:10px;flex-wrap:wrap;margin:15px 0;align-items:center}.lab-form input,.lab-form select,.field{background:var(--card);border:1px solid var(--line);border-radius:6px;padding:10px;color:var(--ink);max-width:100%}.lab-form input{flex:1;min-width:180px}.tool-note{font-size:12px;padding:14px;background:#172331;border-radius:7px}.tool-result{padding:18px 0}.table-wrap{overflow:auto}.graph-drawing{width:100%;max-height:330px;background:#172331;border-radius:9px}.graph-drawing text{font-size:15px;fill:var(--ink);font-family:Georgia}.graph-drawing line{stroke:#779080;stroke-width:2}.graph-drawing circle{fill:#fffdf4;stroke:#31574c;stroke-width:2}.graph-drawing .hl{stroke:#ab6e36;stroke-width:4}.stage-controls{display:flex;gap:10px;align-items:center;margin:14px 0}.answer-feedback{border-left:4px solid var(--green);background:#172331;padding:18px;margin:20px 0}.answer-feedback.incorrect{border-color:#304055;background:#172331}.quiz-select{width:100%;padding:12px;margin:18px 0;border:1px solid var(--line);background:var(--card);border-radius:6px}.summary-line{font-size:13px;display:flex;justify-content:space-between;gap:20px}.question-layout textarea{width:100%;min-height:110px;padding:12px;border:1px solid var(--line);border-radius:6px;background:#172331}.source-table{width:100%;border-collapse:collapse;font-size:12px}.source-table td,.source-table th{padding:9px;border-bottom:1px solid var(--line);text-align:left}.formula-list{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:12px}.formula-card{border:1px solid var(--line);background:var(--card);padding:18px;border-radius:8px}.formula-card strong{display:block;margin-bottom:8px}.formula-card .formula{font-size:13px}.formula-card p{font-size:12px;margin:8px 0}.article strong{color:#b5c5d5}.article table{font-size:12px}.reading .topic-title{font-size:36px}.article h3{font-size:23px}.article p:first-child{font-style:italic}.source-preview{max-width:100%;height:auto;border:1px solid var(--line);border-radius:8px;margin:18px 0}.mobile-only{display:none}.progressbar{height:5px;background:#172331;border-radius:10px;overflow:hidden;margin:10px 0}.progressbar span{display:block;height:100%;background:#172331}.reading-top .pill{white-space:normal}.article pre{white-space:pre-wrap}.nav a{font-size:12px}.sidebar .brand{font-size:16px}dialog{border:1px solid var(--line);border-radius:14px;padding:28px;background:var(--card);color:var(--ink);max-width:720px;width:calc(100% - 30px);max-height:85dvh;box-shadow:0 25px 100px #18281f38}dialog::backdrop{background:#172331}.dialog-close{float:right;font-size:25px;padding:0 5px}.search-box{width:100%;border:1px solid var(--line);padding:13px;background:#172331;border-radius:6px;font:inherit}.search-result{display:block;padding:14px 0;border-bottom:1px solid var(--line)}.search-result strong{display:block}.search-result:hover{color:var(--green)}.skip-link{position:fixed;top:-100px;left:20px;background:#172331;padding:12px;z-index:100}.skip-link:focus{top:10px}.error{color:#b5c5d5}.mobile-dim{display:none}
@media(max-width:1100px){.library{grid-template-columns:210px minmax(0,1fr)}.main{padding:28px}.topbar{padding:0 28px}.method-layout{grid-template-columns:1fr}.grid3,.methods-grid{grid-template-columns:repeat(2,1fr)}.hero h1{font-size:39px}}
@media(max-width:800px){.sidebar{transform:translateX(-100%);transition:transform .2s}.sidebar.open{transform:translateX(0)}.topbar,.main{margin-left:0}.menu-btn{display:block}.mobile-only{display:inline-flex}.topbar{height:68px;padding:0 18px}.main{padding:24px 18px}.top-right{gap:9px}.search-launch{width:auto}.search-launch kbd,.breadcrumb{display:none}.library{display:block}.course-list{display:none;margin-bottom:20px}.course-list.expanded{display:block}.reading{padding:22px}.hero{grid-template-columns:1fr}.hero-copy{padding:26px}.hero-art{min-height:190px;max-height:230px;padding:0 35px}.hero h1{font-size:39px}.lower-grid{grid-template-columns:1fr}.grid3,.methods-grid{grid-template-columns:repeat(2,1fr)}.formula-list{grid-template-columns:1fr}.grid2{grid-template-columns:1fr}.status-grid{grid-template-columns:repeat(2,1fr)}.page-intro{display:block}.quiz-card{padding:23px}.mobile-dim.shown{display:block;position:fixed;inset:0;background:#172331;z-index:14}}
@media(max-width:480px){.grid3,.methods-grid{grid-template-columns:1fr}.chapter-card{min-height:190px}.reading .topic-title{font-size:31px}.hero h1{font-size:36px}.topbar .pill{display:none}.matrix{border-spacing:3px}.matrix button,.matrix td.bit{width:37px;height:37px}.method-title{font-size:35px}.topic-footer{flex-wrap:wrap}.topbar .search-launch{font-size:11px}}
@media print{body{background:#172331;color:#b5c5d5}.sidebar,.topbar,.footer,.button,.filter-row,.no-print,.topic-footer{display:none!important}.main{margin:0;padding:0;max-width:none}.panel,.formula-card{box-shadow:none;border-color:#304055;break-inside:avoid}.formula-list{display:block}.formula-card{margin:10px 0}.article table{display:table;overflow:visible}.library{display:block}.course-list{display:none}.reading{border:0;padding:0}.article{font-size:11pt}.article h3{break-after:avoid}a[href]::after{content:none}}
.lesson-figure{margin:20px 0;padding:18px;background:#172331;border:1px solid var(--line);border-radius:9px}.lesson-figure svg{width:100%;max-height:350px;display:block}.lesson-figure figcaption{font-size:12px;line-height:1.6;color:var(--muted);margin:10px 0 0}.lesson-figure text{font-family:system-ui,sans-serif}

.footer a{text-decoration:underline;text-underline-offset:2px}.footer{font-size:12px}