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@media(min-width:1450px){.site-header{max-width:1330px}.app{max-width:1270px}.workspace-grid{grid-template-columns:minmax(0,1fr) 305px}.subject-tabs{gap:34px}.promo{min-height:126px}.promo-art{width:108px;height:108px}.chapter-toggle{padding:26px 0}}
@media(max-width:1000px){.app{padding:20px 24px 60px}.site-header{padding:0 26px}.workspace-grid{grid-template-columns:minmax(0,1fr) 240px;gap:18px}.desktop-nav{margin-right:0;gap:25px}.subject-tabs{gap:23px}.search-form{width:270px}.page-heading h1{font-size:28px}.page-heading p{font-size:13px}.search-wrap{gap:12px}.counter{min-width:55px}.chapter-title h3{font-size:17px}.panel-header{padding:21px}.chapter-list{padding:0 21px 5px}.promo{padding:22px 15px}.promo strong{font-size:19px}.promo small{font-size:12px}.promo-art{width:80px;height:80px}.side-card{padding:20px}.brand-sub{display:none}}
@media(max-width:760px){body{background:linear-gradient(180deg,#cee5fc 0,#eaf2f8 140px,#f4f6f9 285px)}.site-header{height:68px;padding:0 20px}.brand{gap:7px}.brand strong{font-size:22px}.brand-mark{width:32px;height:34px;border-radius:10px}.brand-mark img{width:24px}.brand-sub{display:block;font-size:12px;padding-left:9px}.desktop-nav,.profile-link{display:none}.app{padding:8px 16px 106px}.page-heading{margin:4px 0 20px;display:block}.heading-copy{display:none}.search-wrap{gap:20px}.counter{min-width:68px;font-size:12px}.counter strong{font-size:25px}.search-form{width:auto;flex:1;height:44px;padding:0 14px;gap:8px}.search-form input{font-size:13px}.search-form .icon{width:22px}.subject-row{margin-bottom:14px;gap:12px}.subject-tabs{gap:23px;padding-bottom:10px}.subject-tab{font-size:18px}.subject-tab.active{font-size:22px}.settings-btn{font-size:12px;padding:6px 9px;gap:6px;background:#ffffff38}.settings-btn .icon{width:15px}.workspace-grid{display:block}.sidebar{display:none}.quick-grid{gap:8px;padding:5px 0 28px}.quick-icon{width:36px;height:40px;border-radius:9px}.quick-icon img{width:24px;height:24px}.quick-item{gap:8px;font-size:13px}.promo-grid{gap:11px;margin-bottom:19px}.promo{min-height:91px;border-radius:16px;padding:20px 13px}.promo strong{font-size:18px}.promo small{font-size:12px;margin-top:5px;max-width:100%}.promo-art{width:70px;height:70px;top:-16px;right:-5px}.panel{border-radius:21px}.panel-header{padding:19px 18px 12px}.panel-header h2{font-size:21px}.panel-header p{font-size:13px}.panel-header .pill{font-size:11px;padding:3px 6px}.chapter-list{padding:0 18px 4px}.chapter-toggle{gap:12px;padding:23px 0}.chapter-num{width:22px;height:22px;font-size:11px}.chapter-title h3{font-size:17px}.chapter-meta{font-size:12px;gap:9px;margin-top:9px}.progress-track{width:46px;height:5px}.chapter-detail{padding-left:34px;font-size:13px}.chapter-detail-footer span{font-size:11px}.source-note{padding:13px 9px 0;font-size:12px}.bottom-nav{display:flex;align-items:center;justify-content:space-around;position:fixed;left:0;right:0;bottom:0;padding:9px 12px max(12px,env(safe-area-inset-bottom));height:calc(67px + env(safe-area-inset-bottom));z-index:10;background:#ffffffed;border-top:1px solid #eff1f5;backdrop-filter:blur(18px)}.bottom-nav a{display:flex;align-items:center;justify-content:center;flex-direction:column;gap:3px;min-width:60px;min-height:45px;color:#8893a2;font-size:11px}.bottom-nav img{width:26px;height:26px;opacity:.64}.bottom-nav a.active{color:#258af1;font-weight:600}.bottom-nav a.active img{opacity:1;filter:invert(46%) sepia(97%) saturate(2245%) hue-rotate(190deg) brightness(101%) contrast(92%)}.section-top{margin:10px 0 22px}.section-top h1{font-size:26px}.section-top p{font-size:13px}.section-top .secondary{padding:8px 11px;font-size:12px}.list-card{padding:17px;gap:12px;border-radius:16px;align-items:flex-start}.list-card h3{font-size:15px}.list-card p{font-size:12px}.card-actions{flex-direction:column;gap:3px}.list-card .small-primary{font-size:12px;padding:6px 9px}.filter-row{gap:7px}.filter-chip{font-size:12px;padding:5px 12px}.quiz-grid{display:flex;flex-direction:column;gap:16px}.quiz-main,.quiz-side{width:100%}.quiz-side{padding:20px}.quiz-side .question-index{grid-template-columns:repeat(10,1fr);gap:7px;margin:15px 0}.index-dot{font-size:12px}.question-card{padding:23px 19px;border-radius:20px}.question-stem{font-size:18px;margin-bottom:23px;line-height:1.9}.question-info{margin-bottom:20px}.option{font-size:15px;padding:13px 12px;gap:11px}.option-letter{width:27px;height:27px;font-size:13px}.quiz-actions{margin-top:24px;gap:9px}.quiz-actions .primary{padding:11px 14px}.hint-button{font-size:13px}.quiz-nav .secondary{padding:10px 14px}.answer-analysis{padding:17px}.answer-analysis p{font-size:14px}.result-hero{padding:23px;align-items:flex-start;gap:13px}.result-score{font-size:38px}.result-score span{font-size:17px}.result-hero h2{font-size:19px}.result-hero p{font-size:12px}.result-actions{gap:7px}.result-actions .primary,.result-actions .secondary{font-size:12px;padding:9px 11px}.stats-grid{gap:10px}.stat-card{padding:18px 13px;border-radius:17px}.stat-card strong{font-size:26px}.stat-card span{font-size:12px}.study-panel{padding:21px 18px}.study-row h3{font-size:15px}.study-row p{font-size:12px}.empty{padding:48px 22px}.empty p{font-size:13px}.profile-hero{margin:8px 0 24px}.profile-hero h1{font-size:25px}.menu-panel{padding:3px 19px}.menu-row{padding:18px 0}.back-button{margin-bottom:12px}.modal{padding:24px}.modal h2{font-size:20px}.setting-choice{font-size:13px}.question-info .pill{font-size:11px}.quiz-bottom-meta{font-size:11px}.eyebrow{font-size:12px}}
@media(max-width:370px){.brand-sub{display:none}.app{padding-left:12px;padding-right:12px}.subject-tabs{gap:19px}.subject-tab{font-size:17px}.settings-btn{padding:6px}.settings-btn span{font-size:11px}.quick-item{font-size:12px}.promo strong{font-size:16px}.promo small{font-size:11px}.chapter-title h3{font-size:16px}.chapter-meta{gap:7px}.chapter-list{padding:0 15px 4px}.panel-header{padding-left:15px;padding-right:15px}.quiz-side .question-index{grid-template-columns:repeat(5,1fr)}.search-wrap{gap:12px}.counter{min-width:56px}.chapter-detail-footer{align-items:flex-start;flex-direction:column}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!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}[hidden]{display:none!important}
/* Keep the mobile rhythm close to the supplied compact study-app reference. */
.promo{overflow:visible}.promo-art{right:2px}
@media(max-width:760px){.site-header{height:52px}.page-heading{margin-bottom:12px}.quick-grid{padding-top:0;padding-bottom:22px}.quick-item{padding:0}.promo{min-height:88px;padding-top:17px;padding-bottom:17px}.panel-header{display:block;position:relative}.panel-header .pill{position:absolute;top:18px;right:18px;margin:0}.panel-header p{padding-right:0}.chapter-toggle{padding-top:17px;padding-bottom:17px}.subject-row{margin-bottom:10px}.promo-art{top:-14px;right:1px}}

/* Consumer app dialogs: touch-first sheets and focused confirmation cards. */
body.dialog-open{overflow:hidden}
.modal{width:min(440px,calc(100% - 40px));padding:28px;border-radius:30px;background:linear-gradient(155deg,#eaf6ff 0,#fff 165px);max-height:calc(100dvh - 48px);overscroll-behavior:contain;box-shadow:0 24px 100px #183d6629;scrollbar-width:thin}
.modal::backdrop{background:rgba(26,43,64,.32);backdrop-filter:blur(7px)}
.modal[open]{animation:dialog-in .22s cubic-bezier(.2,.8,.2,1)}
.sheet-handle{display:none}.modal-header{align-items:flex-start;margin-bottom:8px;gap:12px}.modal-header h2{font-size:23px;line-height:1.4;letter-spacing:-.4px;margin-top:7px}.modal-eyebrow{font-size:11px;font-weight:600;letter-spacing:1.4px;color:#78a0c1}.modal .icon-button{width:32px;height:32px;background:#fff9;flex-shrink:0}.modal .icon-button:hover{background:#e4edf5}.modal-intro{font-size:13px;color:#8999aa;margin:8px 0 25px}.setting-section{margin-top:24px}.setting-section h3{font-size:14px;font-weight:650;margin-bottom:12px}.quantity-options{gap:10px}.modal .setting-choice{border:1.5px solid transparent;background:#f4f6f9;border-radius:17px;padding:17px 8px;transition:background .15s,border-color .15s}.quantity-options strong{display:block;font-size:27px;line-height:1.2;letter-spacing:-.6px}.quantity-options small{font-size:12px;font-weight:500}.quantity-options span{display:block;font-size:11px;color:#8b99a9;margin-top:8px}.modal .setting-choice.active{background:#edf7ff;border-color:#60b4ff;color:#218bea}.quantity-options .active span{color:#62a0d1}.setting-footnote{font-size:11px;color:#96a2b0;line-height:1.7;margin:11px 0 0}.mode-options{display:grid;gap:10px}.modal .mode-choice{display:flex;align-items:center;text-align:left;gap:12px;padding:15px}.mode-icon{width:39px;height:42px;background:#fff;border-radius:12px;display:grid;place-items:center;flex-shrink:0}.mode-icon .icon{width:23px;opacity:.65}.mode-copy{flex:1;min-width:0}.mode-copy strong{display:block;font-size:14px}.mode-copy>span{display:block;font-size:11px;color:#8e9bac;margin-top:5px}.choice-check{width:19px;height:19px;border-radius:50%;border:1.5px solid #d7e0e8;display:grid;place-items:center;flex-shrink:0}.choice-check .icon{width:13px;visibility:hidden}.active .choice-check{background:#349af6;border-color:#349af6}.active .choice-check .icon{visibility:visible;filter:brightness(0) invert(1)}.modal-footer{margin-top:25px}.modal .primary.full{min-height:49px;border-radius:25px;background:linear-gradient(100deg,#45b0fc,#278cf5);box-shadow:0 6px 16px #2894f52b;margin-top:18px;font-size:15px}.modal-footer .primary.full{margin-top:0}.modal-footer>p{text-align:center;color:#a2adba;font-size:11px;margin:11px 0 0}.modal .message-text{margin-top:10px;background:#f3f7fb;border:0;border-radius:19px;padding:17px;font-size:15px;min-height:150px;resize:none}.modal .record-actions .secondary{border:0;background:#eff6fd;color:#5385b0;border-radius:20px}.modal .modal-note{color:#7e8e9f;line-height:1.9}.modal .list-card{background:transparent}.modal--confirm{width:min(340px,calc(100% - 48px));padding:28px 24px 24px;text-align:center}.modal--confirm .modal-header{justify-content:center}.modal--confirm .modal-header h2{font-size:21px}.modal--confirm .icon-button{display:none}.modal--confirm .modal-note{font-size:14px;margin:18px 0 23px}.modal--confirm .result-actions{display:grid;grid-template-columns:1fr 1fr;gap:10px}.modal--confirm .result-actions button{border:0;border-radius:24px;min-height:46px;font-size:14px;padding:10px}.modal--confirm .secondary{background:#edf2f7;color:#788b9f}.modal--confirm .primary{background:#319af6}.modal--confirm .sheet-handle{display:none}
@keyframes dialog-in{from{opacity:0;transform:translateY(14px) scale(.97)}to{opacity:1;transform:none}}
@keyframes sheet-in{from{opacity:0;transform:translateY(45px)}to{opacity:1;transform:none}}
@media(max-width:760px){.modal--sheet{width:100%;max-width:100%;margin:auto 0 0;padding:12px 24px max(25px,env(safe-area-inset-bottom));border-radius:28px 28px 0 0;max-height:calc(100dvh - 24px)}.modal--sheet[open]{animation:sheet-in .25s cubic-bezier(.2,.8,.2,1)}.modal--sheet .sheet-handle{display:block;width:34px;height:4px;border-radius:3px;background:#cbdbe7;margin:0 auto 21px}.modal-header h2{font-size:22px}.modal--confirm{padding:28px 24px 24px}.modal--confirm .modal-header h2{font-size:21px}.modal--sheet .modal-footer{padding-bottom:2px}}
@media(prefers-reduced-motion:reduce){.modal[open]{animation:none}.modal .setting-choice{transition:none}}

/* Narrow screens, touch controls and safe-area resilience. */
.workspace-grid>*,.quiz-grid>*,.search-wrap,.search-form,.chapter-title,.list-card .content{min-width:0}
.question-stem,.answer-analysis,.list-card h3,.modal-note,.mode-copy,.study-row .content{overflow-wrap:anywhere}
audio,video{max-width:100%}
@media(max-width:768px){
 .app{padding-bottom:calc(108px + env(safe-area-inset-bottom))}
 .site-header{padding-left:max(16px,env(safe-area-inset-left));padding-right:max(16px,env(safe-area-inset-right))}
 .search-form input,.fill-input,.modal .message-text{font-size:16px}
 .search-wrap{gap:12px}.search-form{padding-right:6px}.search-form button{min-width:44px;min-height:44px}
 .settings-btn,.subject-tab,.filter-chip,.small-primary,.back-button,.hint-button,.bookmark-button,.modal .icon-button{min-height:44px}
 .bookmark-button,.modal .icon-button{min-width:44px}
 .quiz-side .question-index{grid-template-columns:repeat(auto-fit,minmax(44px,1fr))}.index-dot{min-height:44px;aspect-ratio:auto}
 .quiz-actions,.quiz-nav,.chapter-detail-footer,.section-top{flex-wrap:wrap}
 .chapter-meta{flex-wrap:wrap}.chapter-detail-footer{gap:12px}
 .result-hero{flex-direction:column}.result-score{order:-1}.result-actions button{min-height:44px}
 .study-row{flex-wrap:wrap}.study-row .content{min-width:140px}
 .modal .message-text{scroll-margin-bottom:30px}
 .modal--sheet{max-height:calc(100dvh - 16px)}
 .bottom-nav{padding-left:max(12px,env(safe-area-inset-left));padding-right:max(12px,env(safe-area-inset-right))}
 .promo{min-height:108px;padding-top:32px}.promo-art{width:58px;height:58px;top:-13px}.promo small{line-height:1.6}
}
@media(max-width:370px){.counter{min-width:49px}.search-wrap{gap:8px}.search-form{padding-left:10px;gap:4px}.search-form>img{display:none}.stats-grid{gap:7px}.stat-card{padding:16px 9px}.stat-card span{font-size:11px}.modal--sheet{padding-left:18px;padding-right:18px}.modal-header h2{font-size:20px}.chapter-detail{padding-left:0}.card-actions{flex-direction:row}.list-card{flex-wrap:wrap}.list-card>.content{flex-basis:100%}}
@media(max-height:500px) and (max-width:900px){.modal{max-height:calc(100dvh - 16px)}.sheet-handle{margin-bottom:10px}.modal-header{margin-bottom:5px}}