/* New first-lesson styles only; shared and archived lessons are untouched. */
.fl-page{--ex-paper:#edf4f1;--ex-ink:#20434b;--ex-muted:#57737b;--ex-teal:#197f70;--ex-line:#c0d4cb;font-size:17px}.fl-header{position:sticky;top:0;z-index:40;min-height:68px;padding:11px 24px;gap:19px;background:#0a101df5}.fl-course{display:flex;gap:14px;font-size:12px;color:#c6d4e2}.fl-course>span{color:#8fa8bd}.fl-header-tools{margin-left:auto;display:flex;gap:7px}.fl-header-tools button{font-size:12px;padding:7px 10px;min-height:36px;background:transparent}.fl-layout{display:grid;grid-template-columns:225px minmax(0,1fr);min-height:calc(100dvh - 140px)}.fl-outline{position:sticky;top:68px;height:calc(100dvh - 68px);overflow:auto;padding:24px 16px 95px;background:#0c1422;border-right:1px solid #29394e;align-self:start}.fl-outline-heading{padding:0 8px 18px}.fl-outline-heading>.eyebrow{font-size:9px;letter-spacing:.1em;margin:0 0 9px}.fl-outline-heading h2{font-size:22px;line-height:1.65;font-weight:500;margin:0}.fl-outline-heading>p:last-child{font-size:10px;color:#8fa9bd;margin:9px 0 0}.fl-period-group{margin-bottom:20px}.fl-period-heading{display:flex;justify-content:space-between;color:#a5d5c7;font-size:11px;margin:0 8px}.fl-period-heading strong{font-weight:500}.fl-period-heading span{font-size:10px;color:#7f9eac}.fl-period-title{font-size:11px;color:#879fb4;margin:3px 8px 8px}.fl-activity-link{display:grid;width:100%;grid-template-columns:20px minmax(0,1fr) 36px;align-items:center;gap:7px;border-color:transparent;text-align:left;background:transparent;padding:8px 7px;min-height:47px;font-size:12px;line-height:1.6;margin:3px 0}.fl-activity-link:hover{background:#142537}.fl-activity-link.active{color:#b7ebdb;border-color:#91d8c54a;background:#90d4c111}.fl-activity-number{font-size:10px;color:#708da4}.fl-activity-link small{font-size:9px;color:#8ca6b7;text-align:right}.fl-outline-foot{border-top:1px solid #29384c;padding:14px 7px;font-size:10px;color:#8bb3a6;margin-top:25px}.fl-outline-foot button{width:100%;font-size:11px;margin:10px 0}.fl-outline-foot a{display:block;font-size:11px;color:#9eb5c9;margin:10px 0}.fl-main{padding:25px 38px 120px;min-width:0;max-width:1500px}.fl-meta{display:flex;justify-content:space-between;gap:20px;align-items:center}.fl-meta>.eyebrow{font-size:10px;margin:0;letter-spacing:.07em}.fl-meta>#lesson-progress{font-size:11px;color:#8ba8bc}.fl-heading{margin:18px 0 22px}.fl-time{font-size:10px;color:#8da6bb;margin:0 0 7px}.fl-heading h1{font-size:36px;line-height:1.45;font-weight:600;letter-spacing:.01em;margin:0 0 10px}.fl-heading>p:last-child{font-size:17px;line-height:1.8;color:#bdcbdc;margin:0}.fl-stage{background:var(--ex-paper);color:var(--ex-ink);border:1px solid #bdd3c8;border-radius:16px;padding:23px;min-width:0;box-shadow:0 20px 80px #0002;overflow-wrap:anywhere}.fl-stage:empty{min-height:280px}.fl-stage h2{font-size:24px;font-weight:500;line-height:1.65;margin:0 0 12px}.fl-stage h3{font-size:20px;font-weight:500;line-height:1.6;margin:0 0 8px}.fl-stage p{line-height:1.85}.fl-stage :is(button,input,select,textarea):focus-visible{outline:3px solid #b87a3b;outline-offset:3px}.fl-stage button{color:#275c63;background:#fff;border:1px solid #b5ccc4;min-height:42px;font-size:14px;padding:8px 14px}.fl-stage button:hover{border-color:#4b8f7b;background:#dfeee6}.fl-stage button[aria-pressed=true],.fl-stage button.selected,.fl-stage button.active{color:#fff;background:#197f70;border-color:#197f70}.fl-stage button.ex-primary,.fl-stage button.primary{color:#fff;background:#197f70;border-color:#197f70;min-height:45px;font-size:15px}.fl-stage button:disabled{opacity:.45}.fl-stage :is(input,select,textarea){color:#244b50;background:#fff;border:1px solid #a7c3b7;border-radius:7px;padding:9px 12px;font-size:15px;max-width:100%;min-width:0}.fl-stage textarea{width:100%;line-height:1.8}.fl-stage input[type=range]{padding:0;background:transparent;border:0;accent-color:#197f70;min-height:30px;max-width:100%}.fl-stage input[type=checkbox]{accent-color:#197f70}.fl-stage figure{margin:0}.fl-stage img{max-width:100%;height:auto;display:block;border-radius:9px}.fl-stage svg{max-width:100%;display:block}.fl-stage svg text{font-family:"Microsoft YaHei","PingFang SC",system-ui,sans-serif}.fl-stage details{font-size:12px;color:#50726b;margin-top:12px}.fl-stage summary{cursor:pointer;min-height:30px;line-height:1.8}.fl-stage label{font-size:14px}.ex-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:22px}.ex-cards{display:grid;grid-template-columns:repeat(3,minmax(0,1fr));gap:15px}.ex-panel{background:#fff9;border:1px solid var(--ex-line);border-radius:10px;padding:18px;min-width:0}.ex-panel p{font-size:14px;color:var(--ex-muted);margin:5px 0}.ex-note{font-size:12px!important;line-height:1.85;padding:11px 14px;background:#dcebe3;border-left:3px solid #80a68e;color:#507066;margin:15px 0 0}.ex-question{font-size:22px;line-height:1.7;color:#1d6859;border-top:1px solid var(--ex-line);padding-top:15px;margin:20px 0 0}.ex-toolbar{display:flex;gap:9px;align-items:center;flex-wrap:wrap;margin:0 0 17px}.ex-flow{display:flex;align-items:center;justify-content:center;gap:18px;margin:18px 0}.ex-node{border:1px solid #9cbdaf;background:#f7faf7;border-radius:10px;padding:18px 22px;text-align:center;min-width:100px;font-size:19px}.ex-output{border-left:3px solid #70a290;background:#dcebe3;padding:16px 20px;margin:16px 0;color:#1c6b57;font-size:20px;line-height:1.7}.ex-reveal{border-top:1px solid var(--ex-line);padding-top:15px;margin-top:17px}.ex-badge{display:inline-block;border:1px solid #adc8ba;border-radius:5px;font-size:11px;color:#4e7567;padding:3px 8px;line-height:1.6}.ex-figure{text-align:center;min-width:0}.ex-figure svg{margin:auto}.ex-figure figcaption{font-size:12px;color:#5b7970;margin-top:7px}.ex-chip{display:inline-flex;align-items:center;justify-content:center;font-size:12px;padding:5px 11px;border-radius:20px;background:#dcebe3;color:#2b705d}.ex-strong{font-size:25px;font-weight:600;color:#1a7860}.fl-disclosure{font-size:10px;line-height:1.85;color:#839fac;margin:13px 3px}.fl-reflection{margin-top:17px;border-top:1px solid #2c4054;padding-top:13px;color:#a0bcbb;font-size:12px}.fl-reflection>summary{cursor:pointer;min-height:30px;line-height:1.8}.fl-reflection>summary span{font-size:10px;color:#738e9f;margin-left:12px}.fl-reflection-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px;margin-top:12px}.fl-reflection-grid label{font-size:12px;color:#a0b6c6}.fl-reflection-grid textarea{display:block;width:100%;background:#122030;color:#d6e4e5;border:1px solid #355160;border-radius:8px;padding:10px 13px;line-height:1.85;font-size:14px;margin-top:6px;resize:vertical}.fl-reflection-grid textarea::placeholder{color:#698a9b}.fl-teacher{background:#112a30;border:1px solid #477e72;border-radius:12px;padding:20px 24px;color:#bfdccf;font-size:14px;line-height:1.9;margin-top:20px}.fl-teacher h2{font-size:18px;font-weight:500;margin:0 0 8px}.fl-teacher p{margin:6px 0 13px}.fl-teacher small{font-size:11px;color:#8fb7a7}.fl-break{padding:13px 18px;background:#17332c;border:1px solid #52745c;border-radius:9px;margin:17px 0;color:#b8d9b8;font-size:13px}.fl-break strong{font-weight:500;display:block;font-size:17px}.fl-break span{display:block;margin-top:3px;font-size:12px;color:#96b5a2}.fl-resume{font-size:11px;color:#a8c9ba;margin:12px 0 0}.fl-storage-warning{color:#ffc4a8!important}.fl-controls{position:fixed;z-index:50;bottom:0;left:0;right:0;min-height:73px;padding:12px 27px;background:#0c1423f5;border-top:1px solid #33445a;backdrop-filter:blur(12px);display:flex;align-items:center;gap:20px}.fl-control-hint{font-size:12px;color:#94b1bf}.fl-navigation{display:flex;align-items:center;gap:16px;margin-left:auto}.fl-navigation button{font-size:13px;min-width:120px;min-height:44px}.fl-navigation>span{font-size:10px;color:#7e9bab}.fl-controls #lesson-menu{display:none}.fl-sr-only{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0,0,0,0);white-space:nowrap}.fl-toast{position:fixed;bottom:88px;left:50%;transform:translate(-50%,10px);max-width:90vw;z-index:80;background:#d9efe3;color:#1d5f4b;border:1px solid #89bca7;padding:10px 18px;border-radius:8px;font-size:13px;opacity:0;pointer-events:none;transition:.15s}.fl-toast.visible{opacity:1;transform:translate(-50%,0)}.fl-large .fl-heading h1{font-size:42px}.fl-large .fl-heading>p:last-child{font-size:20px}.fl-large .fl-stage{font-size:20px}.fl-large .fl-stage p{font-size:17px}.fl-large .fl-stage button{font-size:17px}.fl-large .ex-note{font-size:15px!important}.fl-large .ex-node{font-size:23px}.fl-large .ex-panel p{font-size:17px}.fl-page [hidden]{display:none!important}
.ex-grid2col{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:22px}
@media(max-width:650px){.ex-grid2col{grid-template-columns:1fr;gap:15px}}
@media(min-width:1600px){.fl-main{padding:30px 55px 120px}.fl-heading h1{font-size:43px}.fl-heading>p:last-child{font-size:20px}.fl-stage{padding:30px}.ex-panel{padding:23px}.ex-panel p{font-size:16px}.ex-question{font-size:25px}}
@media(max-width:1100px){.fl-layout{grid-template-columns:205px minmax(0,1fr)}.fl-main{padding:22px 25px 110px}.fl-header{gap:12px;padding-left:18px;padding-right:18px}.fl-header .brand img{width:108px;height:32px}.fl-header .preview-label{display:none}.fl-course{font-size:11px;gap:9px}.fl-heading h1{font-size:31px}.fl-stage{padding:19px}.ex-grid{gap:17px}.ex-cards{gap:11px}.ex-panel{padding:14px}.ex-question{font-size:20px}.ex-flow{gap:12px}.ex-node{padding:14px 17px;font-size:17px}}
@media(max-width:800px){.fl-layout{display:block}.fl-outline{display:none;position:fixed;top:67px;bottom:74px;left:0;width:292px;height:auto;z-index:45;box-shadow:30px 0 100px #0009;padding-bottom:25px}.fl-nav-open .fl-outline{display:block}.fl-main{padding:22px 5vw 110px}.fl-controls #lesson-menu{display:block;min-height:44px;font-size:12px}.fl-control-hint{display:none}.fl-navigation{gap:12px}.fl-navigation button{min-width:110px}.fl-heading h1{font-size:32px}.fl-reflection-grid{gap:12px}.ex-cards{grid-template-columns:repeat(2,minmax(0,1fr))}.ex-flow{flex-wrap:wrap}.ex-grid{gap:15px}.fl-course>span{display:none}}
@media(max-width:540px){.fl-header{padding:10px 4vw;gap:10px;min-height:66px;flex-wrap:nowrap}.fl-header .brand img{width:82px;height:26px}.fl-course{display:none}.fl-header-tools{gap:5px}.fl-header-tools button{font-size:10px;min-height:32px;padding:5px 7px}.fl-header-tools #lesson-font-toggle{display:none}.fl-meta>.eyebrow{font-size:9px;letter-spacing:.02em}.fl-meta>#lesson-progress{font-size:10px}.fl-heading{margin:15px 0 17px}.fl-heading h1{font-size:27px;line-height:1.5}.fl-heading>p:last-child{font-size:14px;line-height:1.85}.fl-time{font-size:9px;margin-bottom:7px}.fl-stage{padding:15px;border-radius:12px}.fl-stage h2{font-size:21px}.fl-stage h3{font-size:18px}.fl-stage button{font-size:12px;padding:8px 10px;min-height:40px}.fl-stage button.ex-primary,.fl-stage button.primary{font-size:13px;min-height:44px;padding:10px 13px}.fl-stage label{font-size:12px}.fl-stage :is(input,select,textarea){font-size:14px}.ex-grid{grid-template-columns:1fr;gap:15px}.ex-cards{grid-template-columns:repeat(2,minmax(0,1fr));gap:11px}.ex-panel{padding:13px}.ex-panel p{font-size:12px}.ex-note{font-size:11px!important;padding:9px 11px;margin-top:12px}.ex-question{font-size:18px;margin-top:16px;padding-top:13px}.ex-toolbar{gap:7px;margin-bottom:13px}.ex-flow{gap:9px;margin:14px 0}.ex-node{font-size:15px;padding:12px 14px;min-width:90px}.ex-output{font-size:17px;padding:13px 15px}.ex-reveal{margin-top:13px;padding-top:12px}.ex-figure figcaption{font-size:10px}.ex-badge{font-size:10px}.ex-strong{font-size:22px}.fl-disclosure{font-size:9px;line-height:1.8}.fl-reflection{font-size:11px}.fl-reflection>summary span{display:block;margin-left:15px;font-size:10px}.fl-reflection-grid{grid-template-columns:1fr}.fl-reflection-grid textarea{font-size:14px}.fl-teacher{padding:16px;font-size:13px}.fl-teacher small{font-size:10px}.fl-break{padding:12px 14px}.fl-break strong{font-size:16px}.fl-break span{font-size:11px}.fl-controls{padding:12px 4vw;gap:8px}.fl-controls #lesson-menu{padding:8px;font-size:11px}.fl-navigation{gap:7px}.fl-navigation button{min-width:93px;font-size:12px;padding:10px}.fl-navigation>span{display:none}.fl-large .fl-heading h1{font-size:31px}.fl-resume{font-size:10px;line-height:1.8}.fl-toast{font-size:12px}}
@media(prefers-reduced-motion:reduce){.fl-toast{transition:none}.fl-page{scroll-behavior:auto}}
@media print{.fl-header,.fl-outline,.fl-controls,.fl-reflection,.fl-toast,.fl-resume,.fl-break{display:none!important}.fl-layout{display:block}.fl-main{padding:0}.fl-page{color:#111;background:#fff}.fl-meta,.fl-heading>p:last-child,.fl-time,.fl-disclosure{color:#333}.fl-stage{box-shadow:none}.fl-teacher{display:none!important}}

/* Keep the experiment in view on classroom projectors; text remains readable. */
.fl-meta .fl-time{margin:0;font-size:10px;text-align:center}.fl-meta{flex-wrap:wrap;column-gap:15px;row-gap:3px}.fl-meta>#lesson-progress{margin-left:auto}
@media(min-width:1101px) and (min-height:700px) and (max-height:850px){
 .fl-main{padding-top:14px;padding-bottom:120px;position:relative}.fl-meta{min-height:24px;gap:9px}.fl-meta>.eyebrow{font-size:10px}.fl-meta .fl-time{font-size:10px;margin-left:auto}.fl-meta>#lesson-progress{margin-left:10px}
 .fl-heading{margin:9px 0 14px}.fl-heading h1{font-size:34px;line-height:1.35;margin-bottom:6px}.fl-heading>p:last-child{font-size:17px;line-height:1.7}.fl-stage{padding:17px 20px}.fl-stage .ex-question{margin-top:11px;padding-top:10px;line-height:1.6}.fl-stage .ex-output{padding:11px 15px;margin:11px 0;min-height:0;line-height:1.65}.fl-stage .ex-note{margin-top:10px;padding-top:8px;padding-bottom:8px}.fl-stage .ex-toolbar{margin-bottom:12px}.fl-disclosure{margin:9px 3px}.fl-reflection{margin-top:11px;padding-top:9px}
 .fl-main:has(.fl-break:not([hidden])) .fl-meta{padding-right:252px}.fl-break{position:absolute;right:38px;top:13px;display:flex;align-items:center;gap:9px;min-height:27px;margin:0;padding:3px 9px;border-radius:5px;white-space:nowrap}.fl-break strong{font-size:11px}.fl-break span{font-size:10px;margin:0}
 .fl-resume{position:fixed;left:28px;bottom:26px;z-index:51;margin:0;max-width:540px;font-size:10px;pointer-events:none}.fl-page:has(.fl-resume:not([hidden])) .fl-control-hint{visibility:hidden}
 .fl-outline{padding-top:19px}.fl-outline-heading{padding-bottom:11px}.fl-outline-heading h2{font-size:21px;line-height:1.5}.fl-outline-heading>p:last-child{margin-top:6px}.fl-period-group{margin-bottom:13px}.fl-activity-link{min-height:40px;padding-top:6px;padding-bottom:6px}
}
@media(max-width:540px){.fl-meta{gap:5px}.fl-meta .fl-time{order:3;flex-basis:100%;text-align:left;font-size:9px}.fl-meta>#lesson-progress{margin-left:auto}}
.fl-record-history{font-size:12px;color:#98b6b6;line-height:1.8;margin:12px 0}.fl-record-history summary{cursor:pointer;min-height:28px}.fl-record-history p{margin:7px 0}.fl-record-history>div{padding:9px 14px;border-left:2px solid #436b65;background:#10272b}

.fl-outline-foot .fl-outline-pending{display:block;font-size:11px;color:#8297a7;margin:10px 0;line-height:1.8}
@media(max-width:800px){.fl-page:not(.ai-presenting) .fl-outline{height:calc(100dvh - 141px);max-height:calc(100dvh - 141px);min-height:0;overflow-y:auto;overscroll-behavior:contain;}}