:root{--accent:#168ce9;--ink:#222;--muted:#777;--line:#dedede}*{box-sizing:border-box}body{margin:0;background:#f5f5f5;color:var(--ink);font-family:-apple-system,BlinkMacSystemFont,'Apple SD Gothic Neo','Malgun Gothic',Arial,sans-serif;word-break:keep-all;overflow-wrap:break-word}button,input,select{font:inherit}button{cursor:pointer;color:inherit}button:disabled{cursor:default;opacity:.55}button:focus-visible,select:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #f5bc4e;outline-offset:3px}h1,h2,h3,p{margin:0}p{line-height:1.8}button{border:0;background:none}button:hover{color:#086dbb}button:disabled:hover{color:inherit}.course-app{max-width:760px;margin:auto;min-height:100vh;background:#fff;border-left:1px solid #eee;border-right:1px solid #eee;padding-bottom:55px}.in-lesson .course-app{padding-bottom:100px}.app-header{height:62px;background:#ffffffF7;display:grid;grid-template-columns:1fr 1.2fr 1fr;align-items:center;border-bottom:1px solid var(--line);position:sticky;top:0;z-index:3;padding:0 23px;backdrop-filter:blur(10px)}.app-header h1{font-size:20px;letter-spacing:-.02em;text-align:center;font-weight:650}.app-header button{font-size:17px;padding:10px 0;text-align:left;font-weight:400;color:var(--accent)}.app-header button:last-child{text-align:right}.course-intro{padding:28px 30px;color:var(--muted);font-size:14px;border-bottom:1px solid #eee}.course-intro strong{font-size:17px;color:#444;font-weight:500}.course-intro p{margin-top:5px}.course-intro .availability{font-size:12px;margin-top:17px;line-height:1.7;color:#8b8b8b}.level-group>summary{list-style:none;background:#f8f8f8;padding:21px 30px;display:flex;justify-content:space-between;align-items:center;color:#666;font-size:22px;cursor:pointer;border-top:1px solid #e7e7e7;border-bottom:1px solid #eee}.level-group>summary::-webkit-details-marker{display:none}.level-code{font-size:14px;color:#888;display:flex;gap:18px;align-items:center}.chevron{font-size:20px}.level-goal{font-size:13px;color:var(--muted);padding:15px 30px;border-bottom:1px solid #eee;background:#fcfcfc}.chapter-row{width:100%;display:grid;grid-template-columns:86px 46px 1fr 20px;gap:20px;align-items:center;padding:25px 30px;text-align:left;border-bottom:1px solid var(--line);min-height:133px;color:#222}.chapter-row:hover{background:#fafcff}.chapter-symbol{display:grid;place-items:center;min-height:65px;font-size:27px;color:#acc2d1;letter-spacing:-.05em;font-weight:300}.chapter-number{font-size:48px;font-weight:300;color:var(--accent);line-height:1}.chapter-info>span{font-size:19px;display:block}.chapter-info small{display:block;font-size:13px;line-height:1.7;margin-top:5px;color:#777}.chapter-info .ready,.ready{color:#629746}.chapter-info .planned,.planned{color:#999}.row-chevron{font-size:24px;color:#bbb}.course-note{padding:25px 30px;color:#999;font-size:11px;line-height:1.8}.chapter-intro{padding:28px 30px 23px;background:#fafafa;border-bottom:1px solid var(--line)}.chapter-intro>span{font-size:12px;color:#888}.chapter-intro h2{font-size:24px;font-weight:550;margin:9px 0}.chapter-intro p{font-size:13px;color:#888}.lesson-row{display:grid;grid-template-columns:1fr 55px;border-bottom:1px solid var(--line);padding:0 25px}.lesson-open{text-align:left;padding:24px 5px;display:grid;gap:9px;min-height:125px}.lesson-open>span{font-size:22px;font-weight:400}.lesson-open small{font-size:14px;color:#777}.lesson-open .ready{font-size:12px;color:#629746}.lesson-open .planned{font-size:12px;color:#999}.info-button{font-size:28px;color:var(--accent);font-weight:300;padding:0}.review-row{display:grid;width:100%;gap:10px;text-align:left;background:#fafafa;border-bottom:1px solid var(--line);padding:27px 30px;color:#222}.review-row>span{font-size:22px}.review-row small{font-size:13px;color:#888}.lesson-context{padding:15px 25px 10px;font-size:12px;color:#aaa}.lesson-tabs{position:fixed;bottom:0;left:50%;transform:translateX(-50%);width:min(100%,760px);display:grid;grid-template-columns:repeat(4,1fr);padding:10px 8px calc(12px + env(safe-area-inset-bottom));border-top:1px solid #ddd;background:#ffffffF5;z-index:5;backdrop-filter:blur(10px)}.lesson-tabs button{display:flex;align-items:center;flex-direction:column;gap:5px;color:#aaa;font-size:12px;padding:3px}.lesson-tabs button.active{color:var(--accent)}.lesson-tabs svg{width:29px;height:29px}.sr-only{position:absolute;width:1px;height:1px;margin:-1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}.tutor-feed{padding:8px 25px 20px}.tutor-step{display:grid;grid-template-columns:24px 1fr;gap:9px;margin:13px 0;scroll-margin:80px 0 100px;transition:opacity .2s}.is-playing .tutor-step:not(.current){opacity:.22}.step-replay{padding:0;color:#b8b8b8;font-size:24px;line-height:1;width:24px;height:30px;align-self:center}.current .step-replay{color:var(--accent)}.speech-bubble{position:relative;background:#e4e4e4;padding:16px 19px;border-radius:6px}.speech-bubble:before{content:'';position:absolute;left:-8px;top:14px;border-top:8px solid #e4e4e4;border-left:9px solid transparent}.step-text{font-size:18px;line-height:1.75}.example .speech-bubble{background:#168bf0;color:white}.example .speech-bubble:before{border-top-color:#168bf0;left:auto;right:-8px;border-left:0;border-right:9px solid transparent}.example .step-text{font-size:22px;line-height:1.6;word-break:normal}.step-meaning{color:#fff;margin:10px 0 0;padding-top:10px;border-top:1px solid #ffffff4d;font-size:14px;line-height:1.65}.step-meaning[hidden]{display:none}.current .speech-bubble{box-shadow:0 0 0 3px #dceeff}.practice .speech-bubble{background:#f3eee1}.practice .speech-bubble:before{border-top-color:#f3eee1}.practice-time{display:block;font-size:12px;color:#857245;margin-top:12px}.tutor-end{border-top:1px solid #eee;margin:30px 0 0 33px;padding:24px 0}.tutor-end h3{font-size:15px;font-weight:500;margin-bottom:10px}.tutor-end button,.tutor-footer button{padding:5px 0;font-weight:400;font-size:14px;color:var(--accent)}.tutor-footer{display:flex;justify-content:space-between;align-items:center;color:#aaa;font-size:11px;margin-left:33px;padding:18px 0}.audio-error{font-size:13px;padding:14px 24px;background:#fff2e7;line-height:1.7}.audio-error[hidden]{display:none}.sheet{padding:25px 30px 40px}.small-label{font-size:12px;color:#999;margin-bottom:8px}.objective{font-size:20px;line-height:1.65}.prereq{font-size:12px;color:#999;margin:15px 0 30px}.summary-point{padding:23px 0;border-top:1px solid #eee}.summary-point h2{font-size:19px;font-weight:550;margin-bottom:10px}.summary-point p{font-size:15px;color:#666}.practice-box{padding:20px;background:#f8f5ee;border-radius:8px;margin:15px 0 25px}.practice-box h2{font-size:17px;margin-bottom:10px}.practice-box p{font-size:15px}.practice-box small{display:block;color:#999;margin-top:12px;font-size:11px;line-height:1.7}.next-button{color:var(--accent);padding:12px 0;font-size:17px}.vocab-row{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:25px 30px;border-bottom:1px solid var(--line)}.vocab-row h2{font-size:25px;font-weight:450}.vocab-row p{font-size:15px;color:#777;margin:8px 0}.vocab-row small{font-size:13px;color:#aaa}.vocab-row button{color:var(--accent);display:grid;justify-items:center;gap:4px;font-size:12px;padding:12px}.vocab-row svg{width:25px;height:25px}.quiz-intro{font-size:13px;color:#888;margin-bottom:25px}.question{border:0;border-bottom:1px solid #eee;padding:20px 0;margin:0 0 25px;min-width:0}.question legend{font-size:17px;line-height:1.8;padding:0;font-weight:500}.answer-options{display:grid;gap:9px;margin:16px 0}.answer-option{display:flex;align-items:flex-start;gap:12px;border:1px solid #e3e3e3;border-radius:6px;padding:14px;font-size:15px;line-height:1.6;cursor:pointer}.answer-option input{margin-top:6px;accent-color:var(--accent);flex-shrink:0}.answer-option.correct{background:#f0f6ed;border-color:#b8ceac}.answer-option.wrong{background:#fff0ed;border-color:#edc0b6}.answer-explanation{font-size:13px;line-height:1.8;color:#707070}.listen-question{font-size:14px;color:var(--accent);padding:12px 0}.quiz-result{padding:22px;background:#f4f7fa;border-radius:8px}.quiz-result h2{font-size:22px}.quiz-result p{font-size:14px;color:#777;margin:12px 0}.quiz-result button{font-size:15px;padding:12px 14px 12px 0;color:var(--accent)}.small-note{color:#999;font-size:12px;line-height:1.8;margin:12px 0}.setting-row{display:flex;justify-content:space-between;align-items:center;margin:22px 0;font-size:14px;gap:15px}.setting-row select{font-size:14px;border:1px solid #ddd;padding:8px;border-radius:5px;background:white}.setting-row input{width:19px;height:19px;accent-color:var(--accent)}.menu-link{display:block;width:100%;text-align:left;padding:18px 0;border-bottom:1px solid #eee;color:var(--accent);font-size:15px}dialog{border:1px solid #ddd;border-radius:14px;max-width:500px;width:calc(100% - 32px);padding:27px;background:white;color:#333}dialog::backdrop{background:#18202e66;backdrop-filter:blur(3px)}dialog h2{font-size:22px;font-weight:550;margin:7px 0 18px}dialog p{font-size:15px;margin:12px 0}#close-detail{display:block;color:var(--accent);font-size:17px;padding:15px 0 0;margin-top:12px;width:100%}#toast{position:fixed;bottom:105px;left:50%;transform:translateX(-50%);background:#30363e;color:white;border-radius:8px;padding:12px 20px;z-index:10;max-width:90%;display:none;font-size:13px;line-height:1.7}#toast.visible{display:block}@media(max-width:650px){body{background:white}.course-app{border:0}.app-header{height:55px;padding:0 18px}.app-header h1{font-size:18px}.app-header button{font-size:16px}.course-intro{padding:23px 20px}.course-intro strong{font-size:16px}.level-group>summary{padding:18px 20px;font-size:21px}.level-code{font-size:12px;gap:12px}.level-goal{padding:14px 20px;font-size:12px}.chapter-row{grid-template-columns:48px 32px 1fr 12px;gap:13px;padding:22px 18px;min-height:120px}.chapter-symbol{font-size:22px;min-height:50px}.chapter-number{font-size:43px}.chapter-info>span{font-size:17px;line-height:1.5}.chapter-info small{font-size:11px}.course-note{padding:25px 20px}.chapter-intro{padding:23px 20px}.chapter-intro h2{font-size:22px}.lesson-row{padding:0 18px;grid-template-columns:1fr 40px}.lesson-open{min-height:122px;padding:21px 2px}.lesson-open>span{font-size:21px}.lesson-open small{font-size:13px}.info-button{font-size:27px}.review-row{padding:25px 20px}.review-row>span{font-size:21px}.review-row small{font-size:12px}.lesson-context{padding:13px 20px 6px;font-size:11px}.tutor-feed{padding:6px 16px 20px}.tutor-step{grid-template-columns:20px 1fr;gap:7px;margin:11px 0}.step-replay{font-size:21px;width:20px}.speech-bubble{padding:13px 15px}.step-text{font-size:16px;line-height:1.75}.example .step-text{font-size:20px}.step-meaning{font-size:13px}.tutor-footer,.tutor-end{margin-left:27px}.tutor-footer{font-size:10px}.sheet{padding:22px 20px 35px}.objective{font-size:19px}.summary-point h2{font-size:18px}.summary-point p{font-size:14px}.vocab-row{padding:23px 20px}.vocab-row h2{font-size:24px}.vocab-row p{font-size:14px}.vocab-row small{font-size:12px}.question legend{font-size:16px}.answer-option{font-size:14px;padding:13px}.lesson-tabs{padding-top:9px}.lesson-tabs svg{width:28px;height:28px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}
:root{--accent:#ff4b3c}.tutor-app{background:#f1f1f1}.tutor-feed{padding-top:24px}.tutor-step{display:block;position:relative;margin:13px 0}.speech-bubble{display:block;width:100%;border:0;text-align:left;color:var(--ink);font-weight:400;background:#d9d9d9;cursor:pointer;position:relative;z-index:1;touch-action:manipulation}.speech-bubble:hover{color:var(--ink)}.speech-bubble:before{border-top-color:#d9d9d9}.step-text,.step-meaning{display:block}.current .speech-bubble{box-shadow:none}.is-playing .tutor-step.current:before{content:'';position:absolute;inset:-6px -25px;background:white;z-index:0}.example .speech-bubble:hover{color:white}.tutor-end{margin-left:0}.tutor-footer{margin-left:0}@media(max-width:650px){.tutor-feed{padding-top:24px}.tutor-step{display:block;margin:12px 0}.is-playing .tutor-step.current:before{left:-16px;right:-16px}.speech-bubble{padding:14px 17px}.tutor-footer,.tutor-end{margin-left:0}}
@media(max-width:650px){.tutor-feed{padding-left:24px;padding-right:24px}.is-playing .tutor-step.current:before{left:-24px;right:-24px}}
.subject-switch{float:right;color:var(--accent);font-size:13px;padding:0 0 12px 12px}.catalog-intro h2{font-size:30px;font-weight:550;line-height:1.5;letter-spacing:-.04em}.catalog-intro>p:last-child{margin-top:15px;color:#777;font-size:14px}.subject-row{display:block;width:100%;text-align:left;padding:28px 30px;border-top:1px solid var(--line)}.subject-row h2{font-size:24px;font-weight:500;margin:5px 0 10px}.subject-row p{color:#777;font-size:14px}.subject-action{display:block;margin-top:15px;color:var(--accent);font-size:15px}.concept-tabs{display:flex;border-bottom:1px solid var(--line);background:white;position:sticky;top:62px;z-index:2}.concept-tabs button{flex:1;padding:16px;font-size:15px;color:#888;border-bottom:2px solid transparent}.concept-tabs [aria-current]{color:var(--accent);border-color:var(--accent)}.concept-feed{padding:10px 30px 30px}.concept-block{padding:27px 0;border-bottom:1px solid #e4e4e4;scroll-margin-top:130px}.concept-block h2{font-size:21px;font-weight:550;margin:7px 0 15px}.concept-block>p:not(.small-label){font-size:16px;color:#555}.concept-block.explanation{background:#f5f5f5;padding:24px;margin:20px -8px;border:0;border-radius:6px}.concept-choice{border:0;padding:0;margin:0;min-width:0}.concept-choice legend{font-size:16px;line-height:1.8;padding:0;margin-bottom:18px}.concept-choice .answer-option{margin-bottom:10px}.concept-feedback{font-size:14px;background:#f1f5f7;padding:15px;margin-top:15px;color:#485e6d;line-height:1.8}.evaporation-figure{margin:20px 0 0;border:1px solid #e0e6e8;border-radius:6px;overflow:hidden;background:#fafcfd}.condition-control{display:flex;gap:6px;padding:12px;border-bottom:1px solid #e0e6e8}.condition-control button{flex:1;font-size:13px;padding:10px 6px;border-radius:4px;color:#73818b}.condition-control button[aria-pressed=true]{background:#e4eef3;color:#23485c}.evaporation-scene{width:100%;height:auto;display:block}.evaporation-figure figcaption{padding:20px;background:white;font-size:14px}.evaporation-figure strong{font-weight:550}.evaporation-figure p{margin:8px 0}.evaporation-figure small{display:block;font-size:11px;line-height:1.7;color:#999}.reasoning{padding-left:23px;color:#555;font-size:15px;line-height:1.9}.reasoning li{padding:5px 0}.concept-finish{padding:25px 0;font-size:14px;color:#777}.concept-sources{padding:25px 0;font-size:12px;color:#888;line-height:1.8}.concept-sources summary{cursor:pointer}.concept-sources a{display:block;color:#6c8190;margin:12px 0}.concept-sources p{font-size:11px}@media(max-width:650px){.subject-row{padding:25px 20px}.catalog-intro h2{font-size:27px}.concept-feed{padding:8px 24px 25px}.concept-tabs{top:55px}.concept-block h2{font-size:20px}.concept-block>p:not(.small-label),.concept-choice legend{font-size:15px}.concept-block.explanation{padding:20px;margin:18px -5px}.condition-control{gap:2px;padding:8px}.condition-control button{font-size:12px}.evaporation-figure figcaption{padding:16px}}
.lesson-picture{display:block;margin-top:16px;background:white;border-radius:4px;overflow:hidden;color:#333}.lesson-picture img{display:block;width:100%;height:auto;object-fit:contain}.picture-caption{display:block;padding:12px 14px;font-size:13px;line-height:1.7;background:#fff;color:#666;font-weight:400}.form-visual{display:block;margin-top:15px;padding:6px 14px;background:#ffffffed;border-radius:4px;color:#354454}.form-visual>span{display:flex;justify-content:space-between;gap:20px;padding:10px 0;border-bottom:1px solid #e3e8ec;font-size:17px}.form-visual>span:last-child{border-bottom:0}.form-visual b{font-weight:500}.form-visual>span>span{color:#1474b7}@media(max-width:650px){.lesson-picture{margin-top:13px}.picture-caption{font-size:12px;padding:10px 12px}.form-visual>span{font-size:16px}}
/* Screenshot reference: quiet chapter list, speech bubbles, coral reveal menu. */
:root{--accent:#ff4b3c;--menu-coral:#ee5545;--ink:#111}html{min-height:100%;background:#f5f5f5}body{font-weight:400}button{touch-action:manipulation;-webkit-tap-highlight-color:transparent}button:hover{color:var(--accent)}.course-app{position:relative;z-index:2;border:0;transition:transform 380ms cubic-bezier(.22,.8,.25,1);transform-origin:left center;min-height:100dvh}.app-header{height:64px;padding:0 20px;grid-template-columns:1fr 1fr 1fr;background:#fff;backdrop-filter:none}.app-header h1{font-size:21px;font-weight:600;white-space:nowrap}.app-header button{font-size:20px;font-weight:400;white-space:nowrap}.level-picker{height:48px;display:grid;place-items:center;background:#fafafa;border-bottom:1px solid #f4f4f4}.level-picker select{border:0;background:transparent;color:#626262;font-size:22px;font-weight:400;text-align:center;text-align-last:center;max-width:90%;padding:4px 18px;appearance:none;cursor:pointer}.chapter-row{display:grid;grid-template-columns:82px 42px 1fr;gap:16px;min-height:86px;padding:9px 14px 9px 4px;border-bottom:1px solid #d5d5d5;align-items:center}.chapter-row:hover{background:#fafafa;color:inherit}.chapter-row:active{background:#eee}.chapter-art{display:grid;place-items:center;height:70px;color:#aaa}.chapter-art img{display:block;width:78px;height:68px;object-fit:contain}.chapter-art svg{width:30px;height:38px}.chapter-number{font-size:48px;font-weight:200;color:#ef5545;line-height:1}.chapter-info>span{font-size:18px;line-height:1.25}.chapter-info small{font-size:15px;margin-top:4px;line-height:1.3;color:#666}.chapter-info small.chapter-name{font-size:11px;color:#888;margin-top:4px}.chapter-info .ready,.chapter-info .planned{color:#666;display:flex;align-items:center;gap:8px}.chapter-info i{display:inline-block;border-radius:50%;width:12px;height:12px;background:#83c83e;flex-shrink:0}.chapter-info .planned i{background:#aaa}.tutor-app{background:#f2f2f2}.tutor-feed{padding:26px 24px 22px}.tutor-step{margin:0 0 10px;scroll-margin:85px 0 110px}.speech-bubble{border-radius:4px;background:#d9d9d9;padding:10px 10px;color:#080808}.speech-bubble:before{left:-19px;top:10px;border-top:12px solid #d9d9d9;border-left:20px solid transparent}.step-text{font-size:18px;line-height:1.4;letter-spacing:0;font-weight:400}.example .speech-bubble,.practice .speech-bubble{background:#d9d9d9;color:#080808}.example .speech-bubble:hover{color:#080808}.example .speech-bubble:before,.practice .speech-bubble:before{left:-19px;right:auto;border-top:12px solid #d9d9d9;border-left:20px solid transparent;border-right:0}.example .step-text{font-size:19px;line-height:1.4}.step-meaning{color:#626262;border-color:#bfbfbf;font-size:15px;line-height:1.5;margin-top:9px;padding-top:8px}.practice-time{color:#666}.is-playing .tutor-step:not(.current){opacity:.48}.is-playing .tutor-step.current:before{inset:-5px -24px;background:white}.in-lesson .course-app{padding-bottom:100px}.lesson-tabs{background:#fafafa;backdrop-filter:none;padding:6px 10px calc(12px + env(safe-area-inset-bottom));min-height:78px}.lesson-tabs button{font-size:12px;gap:4px;font-weight:400;color:#999}.lesson-tabs svg{width:31px;height:31px}.lesson-tabs button.active{color:var(--accent)}.app-menu{position:fixed;inset:0;max-width:760px;margin:auto;z-index:1;background:var(--menu-coral);color:white;padding:42px 24px calc(28px + env(safe-area-inset-bottom));display:flex;flex-direction:column}.app-menu[hidden]{display:none}.menu-brand{display:flex;width:68%;align-items:center;justify-content:space-between;gap:16px}.menu-brand strong{font-size:25px;font-weight:650;white-space:nowrap}.menu-brand button{color:white;font-size:34px;font-weight:200;padding:0}.menu-main{display:grid;gap:20px;margin:auto 0;width:65%;transform:translateY(-10px)}.menu-main button{text-align:left;color:white;font-size:25px;font-weight:300;padding:4px 6px}.menu-main button:hover,.menu-bottom button:hover,.menu-brand button:hover{color:white;opacity:.8}.menu-bottom{display:flex;justify-content:space-between;width:68%;gap:12px}.menu-bottom button{color:white;font-size:39px;line-height:1;display:grid;justify-items:center;gap:15px;padding:0}.menu-bottom span{font-size:12px;font-weight:600;white-space:nowrap}.menu-return{position:fixed;left:72%;right:0;top:18.5dvh;height:63dvh;z-index:4}.menu-return[hidden]{display:none}body.menu-open{overflow:hidden;background:var(--menu-coral)}.menu-open .course-app{position:fixed;left:max(0px,calc((100vw - 760px)/2));top:0;width:min(100vw,760px);height:100dvh;overflow:hidden;transform:translateX(72%) scale(.63);box-shadow:none;pointer-events:none}.menu-open .app-header{position:relative}.menu-open .lesson-tabs{position:absolute;left:0;transform:none}.menu-open #toast{display:none}dialog{max-height:80dvh;overflow:auto}.lesson-picture{margin-top:12px}.tutor-footer{padding-bottom:18px}@media(min-width:651px){.chapter-row{min-height:130px;grid-template-columns:130px 68px 1fr;gap:25px;padding:16px 24px}.chapter-art{height:95px}.chapter-art img{width:120px;height:95px}.chapter-number{font-size:64px}.chapter-info>span{font-size:25px}.chapter-info small{font-size:20px}.chapter-info small.chapter-name{font-size:14px}.tutor-feed{padding:30px 40px}.step-text{font-size:23px}.example .step-text{font-size:25px}.speech-bubble{padding:16px 20px}.menu-return{left:calc(50% + 167px);right:max(0px,calc((100vw - 760px)/2))}}@media(max-width:360px){.app-header{padding:0 12px}.app-header button{font-size:17px}.chapter-row{grid-template-columns:66px 34px 1fr;gap:10px}.chapter-art img{width:62px}.chapter-info>span{font-size:17px}.menu-brand strong{font-size:22px}.menu-main button{font-size:23px}.menu-bottom span{font-size:10px}}@media(prefers-reduced-motion:reduce){.course-app{transition:none}}