:root{color-scheme:light;--paper:#fff;--page:#f6f5f1;--ink:#242b30;--muted:#657075;--line:#dedfd9;--orange:#ac491b;--orange-wash:#fcf0e6;--navy:#103c65;--note-fill:#eff7fc;--note-line:#c9dfed;--green:#37664e;--green-wash:#eff6f1;font:16px/1.6 Arial,Helvetica,sans-serif}
*{box-sizing:border-box}body{margin:0;background:var(--page);color:var(--ink)}button,input,select{font:inherit}button,summary,label.section-choice{cursor:pointer}a{color:inherit}button:focus-visible,a:focus-visible,summary:focus-visible,input:focus-visible,select:focus-visible{outline:3px solid #d36b31;outline-offset:4px}button{touch-action:manipulation}[hidden]{display:none!important}.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap;border:0}.skip-link{position:absolute;z-index:10;top:-100px;left:16px;background:var(--navy);color:#fff;padding:10px 18px;border-radius:5px}.skip-link:focus{top:12px}
.site-header{background:var(--paper);border-bottom:1px solid var(--line)}.header-inner{max-width:1180px;margin:auto;padding:22px 32px;display:flex;align-items:center;gap:23px}.brand{font-size:28px;font-weight:750;letter-spacing:-1.3px;line-height:1.1;text-decoration:none;white-space:nowrap}.brand>span{color:var(--orange)}.brand .brand-dot{font-size:32px}.header-divider{height:25px;width:1px;background:var(--line)}.site-label{font-size:13px;color:var(--muted)}.back-link{margin-left:auto;text-decoration:none;font-size:13px;font-weight:600;white-space:nowrap}.back-link:hover{color:var(--orange)}.back-link span{margin-left:7px;font-size:17px}
.page{max-width:1180px;margin:auto;padding:0 32px 56px}.intro{padding:40px 0 32px}.course-meta{display:flex;gap:12px;align-items:center;flex-wrap:wrap;font-size:12px;color:var(--muted)}.board-label{font-size:11px;font-weight:700;letter-spacing:.7px;background:var(--orange-wash);color:var(--orange);border-radius:4px;padding:4px 8px}.pilot-label{border-left:1px solid #c9cec9;padding-left:12px}.intro h1{font-size:clamp(31px,4vw,42px);letter-spacing:-1.1px;line-height:1.18;margin:16px 0 12px;font-weight:700}.intro-copy{margin:0;font-size:16px;color:var(--muted)}#course-picker-wrap{margin-top:15px}#course-picker-wrap label{display:block;font-size:13px}#course-picker{font-size:16px;border:1px solid var(--line);border-radius:5px;padding:9px;background:var(--paper);max-width:100%}
.study-layout{display:grid;grid-template-columns:250px minmax(0,1fr);align-items:start;gap:30px}.sidebar{min-width:0}.section-picker{border:1px solid var(--line);border-radius:9px;background:var(--paper);overflow:hidden}.section-picker>summary{display:flex;align-items:center;gap:8px;list-style:none;padding:17px 15px;font-size:14px;font-weight:700;min-height:54px}.section-picker>summary::-webkit-details-marker{display:none}.picker-count{font-size:11px;font-weight:400;color:var(--muted);margin-left:auto;white-space:nowrap}.chevron{height:7px;width:7px;border-right:1.5px solid currentColor;border-bottom:1.5px solid currentColor;transform:rotate(45deg);margin:0 3px 4px 3px;flex-shrink:0}.section-picker[open]>summary .chevron{transform:rotate(225deg);margin-bottom:0}.section-picker fieldset{border:0;padding:0 8px 8px;margin:0;min-width:0}.section-choice{display:flex;align-items:flex-start;gap:10px;padding:13px 10px;border-radius:5px;margin:2px 0;font-size:14px;line-height:1.45;min-height:70px}.section-choice:hover{background:#f6f6f2}.section-choice:has(input:checked){background:var(--orange-wash)}.section-choice input{appearance:auto;accent-color:var(--orange);width:18px;height:18px;flex:0 0 18px;margin:3px 0 0}.section-choice small{display:block;font-size:11px;color:var(--muted);margin-top:6px}.section-choice .choice-title{font-weight:500}.downloads-panel{margin-top:25px;padding:0 6px}.downloads-panel h2{font-size:12px;letter-spacing:.2px;margin:0 0 7px}.download-link{display:flex;align-items:center;gap:10px;text-decoration:none;padding:13px 0;border-bottom:1px solid var(--line);font-size:13px}.download-link>span:first-child{display:grid;place-items:center;border:1px solid #d4d7d0;background:#fff;border-radius:4px;width:29px;height:34px;font-size:17px;flex-shrink:0;color:var(--orange)}.download-link small{display:block;color:var(--muted);font-size:11px;margin-top:2px}.download-link:hover .download-label{text-decoration:underline;text-underline-offset:3px}.study-note{display:flex;gap:10px;margin:22px 6px 0;color:var(--muted)}.study-note p{font-size:12px;margin:0}.note-icon{font-size:24px;color:var(--orange);line-height:1.2}.loading-copy{font-size:13px;color:var(--muted);padding:10px}
.study-main{min-width:0;scroll-margin-top:20px}.results-toolbar{display:flex;align-items:center;justify-content:space-between;flex-wrap:wrap;gap:5px;margin:0 0 12px;min-height:25px;color:var(--muted);font-size:12px}.results-toolbar p{margin:0}.toolbar-hint{font-size:11px}.lesson{background:var(--paper);border:1px solid var(--line);border-radius:9px;margin-bottom:23px;overflow:hidden}.lesson-toggle>summary{padding:23px 26px;list-style:none;display:flex;align-items:center;gap:15px}.lesson-toggle>summary::-webkit-details-marker{display:none}.lesson-number{width:35px;height:35px;display:grid;place-items:center;font-size:14px;font-weight:700;border:1px solid var(--note-line);background:var(--note-fill);color:var(--navy);border-radius:6px;flex-shrink:0}.lesson-heading{min-width:0;flex:1}.lesson-heading h2{font-size:23px;line-height:1.3;letter-spacing:-.4px;margin:0;color:var(--navy);font-weight:700}.lesson-heading .lesson-meta{font-size:11px;color:var(--muted);margin-top:7px;display:flex;gap:10px;flex-wrap:wrap}.lesson-toggle>summary>.chevron{margin-left:5px;color:var(--muted)}.lesson-toggle[open]>summary>.chevron{transform:rotate(225deg);margin-bottom:0}.lesson-toggle[open]>summary{border-bottom:1px solid var(--line)}.lesson-objective{margin:22px 26px 0;padding:12px 15px;background:var(--note-fill);border:1px solid var(--note-line);border-radius:4px;font-size:13px;line-height:1.55}.lesson-objective strong{display:block;color:var(--navy);margin-bottom:5px;font-size:11px;letter-spacing:.4px}.lesson-body p{margin:8px 0 13px}.lesson-body ul,.lesson-body ol{padding-left:22px;margin:10px 0 15px}.lesson-body li{margin:7px 0}.lesson-body strong{font-weight:700}.cc-content,.cc-practice{padding:24px 26px}.lesson-body h3{display:inline-block;background:var(--navy);color:#fff;font-size:11px;letter-spacing:.8px;padding:5px 10px;margin:0 0 17px;border-radius:2px}.lesson-body h4{font-size:15px;color:var(--navy);margin:20px 0 10px}.cc-definitions{padding:14px 16px;background:var(--note-fill);border:1px solid var(--note-line);border-radius:3px;margin:0}.cc-definitions dt{font-weight:700;font-size:14px;margin-top:12px}.cc-definitions dt:first-child{margin-top:0}.cc-definitions dd{margin:3px 0 10px;font-size:14px}.cc-definitions dd:last-child{margin-bottom:0}.diagram-trigger{display:block;background:#fff;border:1px solid #ecece8;border-radius:6px;padding:12px;max-width:100%;margin:23px auto;color:var(--muted)}.diagram-trigger:hover{border-color:#cb8e6e}.diagram-trigger>span{font-size:11px;display:block;text-align:right;margin:5px 0 0}.cc-original-diagram{display:block;max-width:100%;width:470px;height:auto;margin:auto;background:#fff}.cc-equation{font-size:18px;font-weight:700;padding:12px 15px;text-align:center;color:var(--navy);border:1px solid var(--note-line);background:var(--note-fill);border-radius:3px}.cc-example{margin-top:24px;padding:16px;background:var(--note-fill);border:1px solid var(--note-line);border-radius:4px;font-size:14px}.cc-example-label{font-size:10px;font-weight:700;color:#366889;letter-spacing:.8px}.cc-example h4{margin:5px 0 10px}.cc-answer-strip{background:#e3eef5;padding:11px 13px;border-radius:3px;font-weight:700;color:var(--navy)}.cc-trap{padding:3px 0 3px 13px;border-left:3px solid #bf542d;font-size:13px;margin-top:22px}.cc-trap strong{display:block;color:#a44524;font-size:11px;letter-spacing:.5px;margin-bottom:5px}.cc-practice{border-top:1px solid var(--line)}.cc-practice h3{margin-bottom:8px}.cc-practice .practice-hint{font-size:12px;color:var(--muted);margin:0 0 21px}.cc-question-label{font-size:10px;color:var(--muted);letter-spacing:.5px;font-weight:700;margin-bottom:8px}.cc-question>p{font-size:15px}.cc-question+.cc-question{margin-top:25px;border-top:1px solid var(--line);padding-top:23px}.cc-marks{white-space:nowrap;font-weight:700;font-size:13px}.cc-question details{margin-top:13px}.cc-question summary{display:inline-flex;align-items:center;gap:10px;font-size:13px;min-height:44px;padding:9px 13px;border:1px solid #d9c7b9;border-radius:5px;color:var(--orange);background:#fffaf6;list-style:none;font-weight:700}.cc-question summary::-webkit-details-marker{display:none}.cc-question summary:after{content:'+';font-size:18px;line-height:1;font-weight:400;margin-left:4px}.cc-question details[open]>summary:after{content:'−'}.cc-question details[open]>summary{margin-bottom:10px}.cc-revealed{padding:13px 16px;border-left:3px solid var(--green);background:var(--green-wash);font-size:14px;border-radius:0 4px 4px 0}.cc-revealed p:last-child{margin-bottom:0}.cc-revealed ul{margin-top:0;margin-bottom:0}.cc-done{background:#f4f8f5;border-top:1px solid #dae7dd;padding:15px 26px;font-size:13px;color:var(--green)}.cc-done strong{display:block;font-size:11px;letter-spacing:.5px;margin-bottom:4px}.cc-particle-table{width:100%;border-collapse:collapse;font-size:14px;margin:0 0 17px}.cc-particle-table th,.cc-particle-table td{text-align:left;border-bottom:1px solid var(--note-line);padding:11px 9px}.cc-particle-table th{font-size:12px;background:var(--note-fill);color:var(--navy)}.inline-nuclide{display:inline-flex;align-items:center;white-space:nowrap;vertical-align:middle}.isotope-numbers{display:inline-flex;flex-direction:column;font-size:10px;line-height:1.1;margin-right:2px}.inline-nuclide>sup{align-self:flex-start;font-size:10px}
.empty-state,.load-error{border:1px solid var(--line);border-radius:9px;background:var(--paper);padding:38px 30px}.empty-state h2,.load-error h2{font-size:23px;letter-spacing:-.3px;margin:12px 0 8px}.empty-state p,.load-error p{color:var(--muted);max-width:440px;font-size:15px}.empty-mark{background:var(--orange-wash);color:var(--orange);width:40px;height:40px;border-radius:7px;display:grid;place-items:center;font-size:23px}.empty-state button,.load-error button{border:0;background:var(--navy);color:#fff;padding:11px 15px;border-radius:5px;min-height:44px;font-size:13px;margin-top:10px}.load-error>a{display:block;margin-top:16px;font-size:13px;color:var(--orange)}
.site-footer{border-top:1px solid var(--line);max-width:1116px;margin:0 auto;padding:22px 0 28px;display:flex;justify-content:space-between;align-items:center;gap:15px;font-size:12px;color:var(--muted)}.site-footer>div{display:flex;gap:16px;align-items:center;flex-wrap:wrap}.footer-brand{font-weight:700;color:var(--ink)}.site-footer>a{text-decoration:none}.site-footer>a:hover{text-decoration:underline}dialog{width:min(880px,calc(100% - 28px));max-height:90vh;overflow:auto;border:1px solid var(--line);border-radius:10px;padding:20px;background:white;color:var(--ink);box-shadow:0 15px 80px #0003}dialog::backdrop{background:#12202bbd}.dialog-header{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-bottom:20px}.dialog-header h2{font-size:17px;margin:0}.dialog-header button{min-height:44px;padding:6px 12px;border:1px solid var(--line);border-radius:5px;background:#f6f5f1;font-size:13px}.dialog-header button span{font-size:20px;margin-left:8px}#enlarged-diagram{display:block;width:100%;height:auto;background:#fff}#diagram-description{font-size:12px;color:var(--muted);margin:20px 0 0}
@media(min-width:1000px){.sidebar{position:sticky;top:24px}}
@media(max-width:900px){.page{padding-left:24px;padding-right:24px}.header-inner{padding:21px 24px;gap:16px}.study-layout{grid-template-columns:225px minmax(0,1fr);gap:22px}.lesson-toggle>summary{padding:20px}.lesson-heading h2{font-size:21px}.lesson-objective{margin:20px 20px 0}.cc-content,.cc-practice{padding:20px}.cc-done{padding:15px 20px}.site-footer{margin:0 24px}.site-label{font-size:12px}.brand{font-size:26px}.toolbar-hint{display:none}}
@media(max-width:680px){.header-inner{padding:18px 18px;gap:12px;flex-wrap:wrap}.brand{font-size:25px}.brand .brand-dot{font-size:28px}.header-divider,.site-label{display:none}.back-link{font-size:11px}.back-link span{margin-left:2px}.page{padding:0 16px 30px}.intro{padding:28px 2px 24px}.intro h1{font-size:32px;margin:14px 0 10px}.intro-copy{font-size:14px;line-height:1.65}.course-meta{font-size:11px;gap:9px}.pilot-label{font-size:10px;padding-left:9px}.study-layout{grid-template-columns:1fr;gap:24px}.sidebar{display:grid;grid-template-columns:1fr}.section-picker>summary{padding:14px 15px}.section-choice{min-height:62px;padding:11px 10px}.section-choice small{margin-top:3px}.downloads-panel{margin-top:16px;padding:0 3px}.downloads-panel h2{font-size:11px;margin-bottom:3px}#download-links{display:grid;grid-template-columns:1fr 1fr;gap:13px}.download-link{font-size:12px;padding:10px 0}.download-link>span:first-child{width:25px;height:30px;font-size:15px}.download-link small{font-size:10px}.study-note{display:none}.results-toolbar{margin-bottom:10px;font-size:11px}.toolbar-hint{display:block;font-size:10px}.lesson-toggle>summary{padding:18px 16px;gap:11px;align-items:flex-start}.lesson-number{width:29px;height:29px;border-radius:5px;font-size:12px}.lesson-heading h2{font-size:21px;line-height:1.32}.lesson-heading .lesson-meta{font-size:10px;gap:8px;margin-top:6px}.lesson-toggle>summary>.chevron{margin-top:10px;margin-right:2px}.lesson-objective{margin:17px 16px 0;padding:11px 12px;font-size:12px}.cc-content,.cc-practice{padding:20px 16px}.lesson-body{font-size:15px;line-height:1.65}.cc-definitions{padding:12px}.cc-definitions dt,.cc-definitions dd{font-size:13px}.cc-example{padding:13px;font-size:13px}.cc-example h4{font-size:14px}.cc-answer-strip{padding:10px 11px}.cc-equation{font-size:16px;padding:11px 8px}.cc-done{padding:14px 16px;font-size:12px}.cc-particle-table{font-size:13px}.cc-particle-table th,.cc-particle-table td{padding:9px 5px}.cc-particle-table th{font-size:11px}.cc-question>p{font-size:14px}.cc-question-label{font-size:10px}.cc-revealed{font-size:13px;padding:12px 13px}.cc-question summary{font-size:12px}.diagram-trigger{padding:9px}.site-footer{margin:0 18px;padding:20px 0 26px;align-items:flex-start;font-size:11px}.site-footer>div{gap:4px;flex-direction:column;align-items:flex-start}.site-footer>a{white-space:nowrap}.empty-state,.load-error{padding:27px 22px}.empty-state h2,.load-error h2{font-size:21px}dialog{padding:16px}}
@media(max-width:360px){.header-inner{padding:16px}.brand{font-size:23px}.back-link{font-size:10px}.page{padding-left:12px;padding-right:12px}.intro h1{font-size:29px}.course-meta{gap:7px}.pilot-label{font-size:10px}.download-link{gap:7px}.download-link small{font-size:9px}.lesson-heading h2{font-size:19px}.lesson-toggle>summary{padding:16px 13px;gap:9px}.lesson-number{width:26px;height:26px}.lesson-objective{margin-left:13px;margin-right:13px}.cc-content,.cc-practice{padding:18px 13px}}
@media(prefers-reduced-motion:no-preference){button,a,summary{transition:background-color .15s,border-color .15s,color .15s}}
.selection-actions{display:flex;gap:12px;padding:0 18px 8px}.selection-actions button{font-size:12px;border:0;background:transparent;color:var(--orange);text-decoration:underline;text-underline-offset:3px;padding:5px 0;min-height:34px}.section-picker fieldset{max-height:52vh;overflow-y:auto;overscroll-behavior:contain}.view-notes{display:block;padding:12px 16px;border-top:1px solid var(--line);font-size:13px;font-weight:700;text-decoration:none;color:var(--orange)}.view-notes:hover{background:var(--orange-wash)}.picker-count{font-size:10px}.section-picker>summary{gap:5px}.table-scroll{max-width:100%;overflow-x:auto;margin:15px 0}.table-scroll:focus-visible{outline:2px solid var(--orange);outline-offset:3px}.table-scroll .cc-particle-table{margin-bottom:0}.cc-equation,.cc-answer-strip{overflow-wrap:anywhere}.cc-original-diagram{width:100%;max-width:740px}.cc-question ol[type=a]{padding-left:26px}.question-total{font-size:12px!important;font-weight:700;color:var(--navy)}.teaching-video{margin:22px 0;border:1px solid #d9c7b9;border-radius:6px;background:#fffaf6;padding:0 14px}.teaching-video>summary{padding:14px 0;color:var(--orange);font-size:14px;font-weight:700;min-height:48px;list-style:none}.teaching-video>summary::-webkit-details-marker{display:none}.video-player iframe{display:block;width:100%;aspect-ratio:16/9;min-height:200px;border:0;background:#101820;border-radius:4px}.video-fallback{display:block;padding:12px 0;font-size:12px;color:var(--orange)}#course-picker-wrap label{font-weight:700;margin-bottom:5px}#course-picker{width:min(460px,100%)}.cc-question .diagram-trigger{margin:16px auto}
@media(max-width:680px){.section-picker fieldset{max-height:55vh}.selection-actions button{min-height:44px}.intro{padding-bottom:20px}.study-layout{gap:20px}.cc-original-diagram{min-width:0}.table-scroll .cc-particle-table{font-size:12px}.picker-count{font-size:11px}.section-picker>summary{gap:8px}}

.edit-videos-link{font-size:12px;font-weight:700;color:var(--orange);text-decoration:none;margin-left:auto;white-space:nowrap}.edit-videos-link+.back-link{margin-left:0}.draft-preview-banner{background:#fff0df;border-bottom:1px solid #e7c6a4;padding:14px 30px;display:flex;gap:18px;align-items:center;justify-content:center;font-size:13px}.draft-preview-banner a{font-weight:bold}.video-load-warning{color:#8a2823;font-size:13px}@media(max-width:680px){.draft-preview-banner{padding:12px 18px;flex-wrap:wrap;gap:5px 12px}.edit-videos-link{margin-left:auto}.edit-videos-link+.back-link{display:none}}
/* Compact video previews, shared by all lesson sections and draft previews. */
.teaching-video>.video-summary{display:flex;align-items:center;gap:14px;padding:12px 0;line-height:1.45}
.video-thumbnail{position:relative;display:block;width:96px;aspect-ratio:16/9;flex:0 0 96px;overflow:hidden;border-radius:4px;background:#e9ded3;box-shadow:inset 0 0 0 1px #0000000d}
.video-thumbnail img{display:block;width:100%;height:100%;object-fit:cover}
.video-thumbnail-play{position:absolute;inset:0;display:flex;align-items:center;justify-content:center;color:#fff;font-size:12px;line-height:1;padding-left:2px;isolation:isolate}
.video-thumbnail-play::before{content:"";position:absolute;width:28px;height:28px;background:#18242cdb;border:1px solid #ffffffcc;border-radius:50%;z-index:-1}
.video-caption{display:block;flex:1;min-width:0}
.video-prompt{display:block;font-size:11px;font-weight:400;color:var(--muted);margin-bottom:3px}
.video-title{display:block;font-size:14px;font-weight:700;overflow-wrap:anywhere}
.video-chevron{margin-left:auto;flex:0 0 7px;color:var(--orange)}
.teaching-video[open]>.video-summary .video-chevron{transform:rotate(225deg);margin-bottom:0}
.video-summary:hover .video-title{text-decoration:underline;text-underline-offset:3px}
@media(max-width:680px){.teaching-video>.video-summary{gap:10px}.video-thumbnail{width:80px;flex-basis:80px}.video-title{font-size:13px}.video-prompt{font-size:10px}.video-thumbnail-play::before{width:25px;height:25px}}
/* Reveal topic, subtopics and content types in reading order. */
.study-controls{margin:0 0 12px}
.study-controls #course-picker-wrap{margin:0;min-width:0}
.study-controls #course-picker{width:100%;min-height:44px}
.content-filters{border:0;padding:0;margin:12px 0 0;min-width:0}
.content-filters legend{font-size:13px;font-weight:700;padding:0;margin-bottom:5px}
.content-filter-options{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:5px}
.content-filter-options label{display:flex;align-items:center;justify-content:center;gap:5px;min-height:38px;padding:6px 4px;border:1px solid var(--line);border-radius:5px;background:var(--paper);font-size:12px;cursor:pointer}
.content-filter-options label:has(input:checked){background:var(--orange-wash);border-color:#cf9a7e;color:#873b19}
.content-filter-options input{width:16px;height:16px;margin:0;accent-color:var(--orange);flex:0 0 16px}
.lesson-videos{padding:4px 26px 10px}
.no-content-message{padding:22px 26px;color:var(--muted);font-size:14px}
@media(max-width:900px){.lesson-videos{padding:4px 20px 10px}}
@media(max-width:680px){.content-filter-options label{min-height:44px;font-size:13px}.lesson-videos{padding:2px 16px 6px}.no-content-message{padding:16px}}
/* One compact topic selector spans the original Atomic Structure booklets. */
.picker-heading{font-size:16px;line-height:1.35;margin:0 0 12px;font-weight:700;letter-spacing:-.2px}
.section-picker>summary{gap:12px;padding:10px 12px;font-size:14px;min-height:44px}
.section-picker>summary .chevron{margin-left:auto}
.section-picker fieldset{padding:0 5px 5px;max-height:none;overflow:visible}
.section-choice{align-items:center;min-height:0;padding:3px 8px;gap:9px;margin:0;font-size:13px;line-height:1.45}
.section-choice input{width:16px;height:16px;flex-basis:16px;margin:0}
.section-choice>span{min-width:0;overflow-wrap:anywhere}
.section-choice .choice-title{font-weight:400}
.selection-actions{padding:0 13px 3px;gap:16px}
.selection-actions button{min-height:28px;padding:3px 0}
.picker-footer{display:flex;align-items:center;flex-wrap:wrap;gap:8px 12px;padding:7px 12px;border-top:1px solid var(--line)}
.picker-footer .picker-count{font-size:11px;margin:0;white-space:normal}
.picker-footer .view-notes{font-size:11px;padding:0;border:0;margin-left:auto}
.lesson-part+.lesson-part{border-top:1px solid var(--line)}
.lesson-body .lesson-part-title{display:block;background:none;border-radius:0;letter-spacing:normal;font-size:19px;line-height:1.4;margin:0;padding:24px 26px 0;color:var(--navy);font-weight:700}
.lesson-part-title+.lesson-objective{margin-top:14px}
@media(min-width:901px){.study-layout{grid-template-columns:290px minmax(0,1fr)}}
@media(min-width:681px){.sidebar{position:static}}
@media(max-width:900px){.lesson-body .lesson-part-title{padding:20px 20px 0;font-size:18px}}
@media(max-width:680px){.picker-heading{margin-bottom:10px}.lesson-body .lesson-part-title{padding:20px 16px 0;font-size:18px}.picker-footer .view-notes{min-height:28px;display:flex;align-items:center}}
@media(pointer:coarse){.section-choice{min-height:0;padding-top:6px;padding-bottom:6px}.selection-actions button,.content-filter-options label{min-height:44px}}

.analytics-link{font-size:12px;font-weight:700;color:var(--orange);text-decoration:none;white-space:nowrap;margin-left:auto}.analytics-link+.edit-videos-link{margin-left:0}.analytics-settings{background:transparent;border:0;text-decoration:underline;font-size:12px;color:var(--muted);padding:8px}.analytics-choice{position:fixed;z-index:20;bottom:16px;left:16px;right:16px;max-width:900px;margin:auto;background:#fff;border:1px solid var(--line);box-shadow:0 8px 32px #15253426;border-radius:8px;padding:20px;display:flex;gap:24px;align-items:center}.analytics-choice p{font-size:12px;line-height:1.6;margin:5px 0 0}.analytics-choice strong{font-size:14px}.analytics-choice-actions{display:flex;gap:10px;flex-shrink:0}.analytics-choice button{padding:10px 14px;border:1px solid var(--orange);border-radius:5px;background:#fff;color:var(--orange);white-space:nowrap;font-size:13px;font-weight:bold}.analytics-choice button:last-child{background:var(--orange);color:#fff}.site-footer{flex-wrap:wrap}@media(max-width:680px){.analytics-choice{display:block;padding:16px;bottom:8px;left:8px;right:8px;max-height:60vh;overflow:auto}.analytics-choice-actions{margin-top:12px}.header-inner{flex-wrap:wrap;gap:14px}.analytics-link~.back-link{display:none}}

/* Reduce vertical gaps without shrinking lesson text or touch targets. */
.header-inner{padding-top:16px;padding-bottom:16px}
.intro{padding:26px 0 18px}.intro h1{margin:12px 0 8px}
#view-content{margin-top:4px;padding:7px 0;border:0;min-height:34px;font-size:12px}
.downloads-panel{margin-top:18px}.download-link{padding-top:10px;padding-bottom:10px}
.study-note{margin-top:16px}.lesson{margin-bottom:9px}
.lesson-toggle>summary{padding:18px 22px}
.lesson-objective{margin-top:16px}.cc-content,.cc-practice{padding-top:18px;padding-bottom:18px}
.lesson-body .lesson-part-title{padding-top:18px}.lesson-part-title+.lesson-objective{margin-top:12px}
.lesson-body p{margin-top:6px;margin-bottom:10px}.cc-example{margin-top:18px}
.diagram-trigger{margin-top:18px;margin-bottom:18px}
.cc-question+.cc-question{margin-top:20px;padding-top:18px}
.cc-done{padding-top:12px;padding-bottom:12px}
.empty-state,.load-error{padding:26px 24px}
@media(min-width:681px) and (max-width:900px){.study-layout{grid-template-columns:260px minmax(0,1fr)}}
@media(max-width:680px){.header-inner{padding-top:14px;padding-bottom:14px}.intro{padding:20px 2px 16px}.intro h1{margin:10px 0 7px}.study-layout{gap:16px}.lesson-toggle>summary{padding:14px 16px}.lesson-objective{margin-top:14px}.cc-content,.cc-practice{padding-top:16px;padding-bottom:16px}.lesson-body .lesson-part-title{padding-top:16px}.empty-state,.load-error{padding:22px 18px}#view-content{min-height:44px}.downloads-panel{margin-top:14px}}
@media(pointer:coarse){#view-content{min-height:44px}}

/* Full booklets follow the entire study area, never the selection controls. */
.page>.downloads-panel{margin:24px 0 0;padding:16px 0 0;border-top:1px solid var(--line)}
.page>.downloads-panel h2{font-size:16px;margin-bottom:6px}
#download-links{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:0 20px}
@media(max-width:900px){#download-links{grid-template-columns:repeat(2,minmax(0,1fr));gap:0 16px}}
@media(max-width:500px){#download-links{grid-template-columns:1fr}}

/* Original CrackingChem logo, with compact header spacing. */
.header-with-logo{padding-top:6px;padding-bottom:6px}
.header-with-logo .brand{display:block;flex-shrink:0;width:228px;max-width:100%}
.brand-logo{display:block;width:100%;height:auto}
@media(max-width:680px){.header-with-logo{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:0 12px}.header-with-logo .brand{grid-column:1;grid-row:1 / span 2;width:210px}.header-with-logo .analytics-link{grid-column:2;grid-row:1;margin-left:0}.header-with-logo .edit-videos-link{grid-column:2;grid-row:2;margin-left:0}.header-with-logo .analytics-link,.header-with-logo .edit-videos-link{display:flex;align-items:center;min-height:32px}}

.board-picker{border:0;margin:0 0 12px;padding:0;min-width:0}.board-picker legend{font-size:13px;font-weight:700;margin-bottom:5px;padding:0}.board-options{display:grid;grid-template-columns:1fr 1fr;gap:5px}.board-options label{display:flex;align-items:center;gap:8px;min-height:44px;padding:8px 12px;border:1px solid var(--line);border-radius:5px;background:var(--paper);cursor:pointer;font-size:14px}.board-options label:has(input:checked){background:var(--orange-wash);border-color:#cf9a7e;color:#873b19}.board-options input{margin:0;accent-color:var(--orange)}

.video-board-note{margin:8px 0 18px;padding:10px 12px;border-left:3px solid var(--orange);background:var(--orange-wash);color:var(--navy);font-size:13px;line-height:1.55;overflow-wrap:anywhere}

.signup-panel{margin-top:26px;padding:20px 22px;border:1px solid var(--note-line);border-radius:8px;background:var(--note-fill);display:flex;align-items:center;gap:22px}
.signup-panel>div{flex:1;min-width:0}.signup-panel h2{font-size:18px;line-height:1.35;color:var(--navy);margin:0 0 6px}.signup-panel p{font-size:13px;line-height:1.6;margin:0}
.signup-panel>a{display:flex;align-items:center;justify-content:center;min-height:44px;padding:10px 15px;background:var(--navy);color:#fff;border-radius:5px;font-size:13px;font-weight:700;text-decoration:none;text-align:center}
.signup-panel>a:hover{text-decoration:underline;text-underline-offset:3px}
@media(max-width:680px){.signup-panel{display:block;padding:18px}.signup-panel>a{margin-top:14px}}

/* Key chemistry remains easy to find in every topic and on small screens. */
.cc-definitions,.cc-equation,.cc-key-point{border:2px solid #2782b5;border-radius:8px;background:#eaf5fd;box-shadow:0 2px 0 #103c6508}
.cc-definitions{padding:15px 17px;margin:14px 0 18px}
.cc-definitions::before{content:"DEFINITIONS & KEY TERMS";display:block;color:var(--navy);font-size:10px;font-weight:700;letter-spacing:.8px;margin-bottom:10px}
.cc-definitions dt{color:var(--navy);font-size:15px}
.cc-definitions dd{font-size:14px;line-height:1.65}
.cc-equation{padding:13px 16px;margin:13px 0 17px;line-height:1.6;color:#073c69;overflow-wrap:anywhere}
.cc-working{margin:10px 0 14px;padding:0;border:0;background:none;box-shadow:none;text-align:left;font-size:1rem;font-weight:400;line-height:1.7;overflow-wrap:anywhere}
.cc-symbol-key{display:block;margin:7px 0 12px;font-size:13px;font-weight:400;line-height:1.65;color:#42586a;text-align:left}
.cc-equation>.cc-symbol-key{margin:9px 0 0;font-size:13px;font-weight:400}
.cc-working>.cc-symbol-key{margin:4px 0 0}
.cc-calculation-table{min-width:0;width:100%;table-layout:auto}
.cc-calculation-table th,.cc-calculation-table td{padding:6px 12px;line-height:1.45;vertical-align:top}
.cc-calculation-table th:first-child,.cc-calculation-table td:first-child{font-weight:600}
.cc-calculation-wide{min-width:540px}
.cc-calculation-wide th:first-child,.cc-calculation-wide td:first-child{min-width:160px}
.cc-key-point{padding:14px 17px;margin:14px 0 18px;overflow-wrap:anywhere}
.cc-key-label{display:block;font-size:11px;letter-spacing:.6px;color:var(--navy);margin-bottom:8px}
.cc-key-point>p:first-of-type{margin-top:0}.cc-key-point>p:last-child{margin-bottom:0}
.cc-key-point.cc-definition::before{content:"KEY DEFINITION";display:block;font-size:10px;letter-spacing:.7px;font-weight:700;color:var(--navy);margin-bottom:8px}
.cc-exception,.cc-trap{border:2px solid #b94c42;background:#fff2ee;border-radius:8px;padding:14px 17px;margin:16px 0 18px;color:var(--ink);box-shadow:0 2px 0 #71322608}
.cc-exception .cc-key-label,.cc-trap>strong{color:#922f29;font-size:11px;letter-spacing:.6px}
.cc-definitions.cc-exception::before{content:"EXCEPTIONS TO THE TREND";color:#922f29}
.cc-exception dt{color:#922f29}
.cc-key-point .table-scroll:last-child{margin-bottom:0}
@media(max-width:680px){.cc-definitions,.cc-key-point,.cc-trap{padding:12px 13px}.cc-equation{font-size:16px;padding:11px 12px}.cc-definitions dt{font-size:14px}}

/* Owner-approved teaching panels: navy examples, copper student questions. */
:root{--copper:#9f4b25;--copper-wash:#fff8f3}
.cc-example{--panel-ink:#103c65;margin:18px 0 22px;padding:0;border:0;border-radius:0;background:transparent;font-size:15px}
.cc-example-label{display:block;background:#103c65;color:#fff;font-weight:700}
.cc-example .cc-example-title{margin:0 0 8px;font-size:16px;line-height:1.45}
.cc-example .cc-worked-answer-heading{margin:17px 0 7px;padding:0;border:0;font-size:14px;line-height:1.5}
.cc-example-answer .cc-answer-strip{padding:0;border:0;border-radius:0;background:transparent;box-shadow:none}
.cc-example-question>p:last-child{margin-bottom:0}
.cc-practice{margin:4px 26px 20px;padding:0;border:0;background:transparent}
.cc-practice>h3{display:block;margin:0 0 12px;padding:10px 14px;border-radius:0;background:var(--copper);color:#fff;font-size:13px;line-height:1.5;letter-spacing:.35px}
.cc-question{--panel-ink:var(--copper);min-width:0;border:0;padding:0;background:transparent;overflow-wrap:anywhere}
.cc-question+.cc-question{margin-top:20px;border:0;padding-top:0}
.cc-question-label{display:block;font-size:13px;color:var(--copper);letter-spacing:0;font-weight:700;margin-bottom:8px}
.cc-example-question,.cc-question-prompt{min-width:0;padding:0 14px 14px;border:1.5px solid var(--panel-ink);border-radius:0;background:var(--paper);overflow-wrap:anywhere}
.cc-example-question>.cc-example-label,.cc-question-prompt>.cc-question-label{display:block;margin:0 -14px 12px;padding:10px 14px;border:0;border-radius:0;background:var(--panel-ink);color:#fff;font-size:13px;font-weight:700;line-height:1.5;letter-spacing:.35px;text-transform:uppercase}
.cc-example-question>p,.cc-question-prompt>p{margin:8px 0 13px;font-size:15px;line-height:1.6}
.cc-example-question>:last-child,.cc-question-prompt>:last-child{margin-bottom:0}
.cc-question>details{max-width:100%}
.cc-question summary{max-width:100%;white-space:normal;border-color:var(--copper);color:var(--copper);background:var(--copper-wash)}
.cc-figure{margin:15px 0}
.cc-figure>.diagram-trigger{margin-bottom:7px}
.cc-figure>.cc-symbol-key{margin-top:0}
@media(max-width:900px){.cc-practice{margin-left:20px;margin-right:20px}}
@media(max-width:680px){.cc-practice{margin-left:16px;margin-right:16px;padding:0}.cc-example-question,.cc-question-prompt{padding-left:12px;padding-right:12px}.cc-example-question>.cc-example-label,.cc-question-prompt>.cc-question-label{margin-left:-12px;margin-right:-12px}.cc-example-question>p,.cc-question-prompt>p{font-size:14px}.cc-calculation-table th,.cc-calculation-table td{padding:6px 10px}}
@media(max-width:360px){.cc-practice{margin-left:13px;margin-right:13px}}

/* One compact opener per main topic, independent of lesson filters. */
.topic-opener{display:flex;align-items:center;gap:18px;max-width:640px;margin:16px 0 20px;padding:12px 18px;background:var(--paper);border-left:3px solid var(--orange);border-radius:0 8px 8px 0}
.topic-opener img{width:96px;height:96px;object-fit:contain;flex:none}
.topic-opener-art{display:flex;align-items:center;justify-content:center;width:112px;height:96px;flex:none}
.topic-opener-illustration{display:block;width:100%;background-repeat:no-repeat}
.topic-opener p{min-width:0;overflow-wrap:break-word}
.section-opener{margin-top:0;max-width:100%}
.topic-opener p{margin:0;line-height:1.5;color:var(--navy)}
.topic-opener strong,.topic-opener span{display:block}
.topic-opener span{margin-top:4px;color:var(--ink)}
@media(max-width:480px){.topic-opener{gap:12px;padding:10px 12px}.topic-opener img{width:72px;height:72px}.topic-opener-art{width:80px;height:72px}.topic-opener p{font-size:14px}}