:root{--paper:#fffdf7;--ink:#123d2f;--muted:#49695c;--green:#20573f;--line:#dae1d6;--sage:#f0f7e8;--peach:#fff0e6;--blue:#e9f6ff;--lavender:#f0ebff;--radius:22px;--focus:#225fb1;--font:'Trebuchet MS',Arial,sans-serif}
*{box-sizing:border-box}body{margin:0;background:var(--paper);color:var(--ink);font-family:var(--font);font-size:19px;line-height:1.5}button,input,select,textarea{font:inherit}button,a{-webkit-tap-highlight-color:transparent}button{cursor:pointer;color:inherit}a{color:inherit;text-decoration:none}button:disabled{cursor:default;opacity:.52}button,select,input{min-height:46px}svg{width:24px;height:24px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;flex-shrink:0}h1,h2,h3,p{margin-top:0}h1{font-size:clamp(34px,4.6vw,64px);line-height:1.12;letter-spacing:-1.9px;margin-bottom:16px;font-weight:800}h2{font-size:30px;line-height:1.25;letter-spacing:-.6px;margin-bottom:12px}h3{font-size:31px;line-height:1.2;letter-spacing:-.65px;margin-bottom:8px}p{margin-bottom:16px}:focus-visible{outline:3px solid var(--focus);outline-offset:5px}main:focus{outline:none}main{max-width:1240px;margin:auto;padding:0 30px}button{border:0;background:none}.skip-link{position:fixed;top:-90px;left:10px;z-index:10;background:#fff;padding:10px}.skip-link:focus{top:10px}.topbar{height:76px;border-bottom:1px solid #e1e4dc;display:flex;align-items:center;justify-content:space-between;padding:0 40px;background:rgba(255,255,255,.36)}.brand{display:flex;align-items:center;gap:12px;font-size:22px;font-weight:800}.brand span{font-size:32px}.top-tools{display:flex;align-items:center;gap:28px;font-size:20px;font-weight:700}#stars{display:flex;align-items:center;gap:10px}#stars span{font-size:28px}.icon-button{display:grid;place-items:center;border-left:1px solid var(--line);padding-left:25px;min-width:60px}.icon-button svg{width:29px;height:29px}.welcome{position:relative;display:flex;align-items:center;min-height:243px;padding:34px 24px 28px}.welcome>div{z-index:1}.welcome h1{font-size:clamp(34px,4.4vw,62px);max-width:830px}.subtitle{font-size:clamp(22px,2.6vw,34px);color:var(--muted);margin:0;line-height:1.3;letter-spacing:.2px}.art{display:block;flex-shrink:0;background-image:url('assets/science-art.png');background-size:300% 200%;background-repeat:no-repeat;width:210px;height:210px}.art-living{background-position:0 0}.art-cycles{background-position:50% 0}.art-materials{background-position:100% 0}.art-magnets{background-position:0 100%}.art-hero{background-position:50% 100%}.art-sprout{background-position:100% 100%}.hero-art{width:290px;height:290px;position:absolute;right:-8px;top:0;z-index:0}.welcome>div{max-width:calc(100% - 200px)}.world-picker>h2{margin:0 24px 6px;font-size:34px}.intro{font-size:21px;color:var(--muted);margin-left:24px;margin-bottom:24px}.world-grid{display:grid;grid-template-columns:1fr 1fr;gap:18px}.world-card{position:relative;display:flex;align-items:center;min-height:202px;border:1.5px solid;padding:18px 58px 18px 4px;border-radius:var(--radius);transition:transform .18s,box-shadow .18s}.world-card:hover{transform:translateY(-3px);box-shadow:0 8px 20px #00000012}.sage{background:var(--sage);border-color:#a3bf90}.peach{background:var(--peach);border-color:#eeb296}.blue{background:var(--blue);border-color:#93c6e9}.lavender{background:var(--lavender);border-color:#b3a2dd}.world-card .art{width:185px;height:185px}.world-info{flex:1;min-width:0}.world-info>p{color:var(--muted);font-size:18px;line-height:1.35;min-height:49px;margin-bottom:18px}.world-progress{font-size:16px;font-weight:700;padding-right:10px}.progress-track{height:12px;background:#123d2f14;border-radius:8px;margin-top:9px;overflow:hidden}.progress-track>span{display:block;height:100%;background:var(--green);border-radius:8px}.world-arrow{position:absolute;right:20px;bottom:24px;width:48px;height:48px;display:grid;place-items:center;border-radius:50%;background:var(--green);color:white}.discovery-note{display:flex;gap:18px;align-items:center;justify-content:center;margin:27px 0 18px;color:var(--muted);font-size:18px}.discovery-note>span{font-size:42px}.discovery-note strong{font-size:20px;color:var(--ink)}.discovery-note p{margin:0}footer{text-align:center;color:#668777;padding:12px 20px 24px;font-size:15px;display:flex;align-items:center;justify-content:center;gap:16px}.resume-row{display:flex;align-items:center;justify-content:space-between;gap:12px;margin-top:22px;font-size:15px;color:var(--muted)}.text-button{color:var(--green);text-decoration:underline;text-underline-offset:4px;padding:8px 2px;font-size:17px;display:inline-flex;align-items:center;gap:10px}.text-button svg{width:19px}.primary,.secondary{display:inline-flex;align-items:center;justify-content:center;gap:12px;min-height:52px;padding:12px 24px;border-radius:13px;font-size:19px;line-height:1.3;font-weight:700;text-align:center}.primary{background:var(--green);color:white;border:2px solid var(--green)}.primary:hover:not(:disabled){background:#143e2d}.secondary{border:2px solid #83a28d;background:white}.back-link{display:inline-flex;align-items:center;min-height:48px;margin-top:22px;color:var(--muted);font-size:18px}.world-heading{display:flex;justify-content:space-between;align-items:center;margin-top:12px;padding:0 20px}.world-heading h1{font-size:44px}.world-heading .art{width:195px;height:195px}.world-heading p:last-child{font-size:17px;margin-top:20px}.activity-list{max-width:850px;margin:0 auto 30px;display:grid;gap:10px}.activity-row{display:flex;align-items:center;gap:20px;padding:17px 24px;border:1px solid var(--line);background:#fff;border-radius:17px}.activity-row:hover{border-color:#74a17f;background:#f5faef}.activity-number{width:46px;height:46px;border-radius:50%;background:#eef5e7;display:grid;place-items:center;font-weight:700;flex-shrink:0}.activity-row h2{font-size:22px;margin:0 0 2px}.activity-row p{font-size:15px;color:var(--muted);margin:0}.activity-row>span:last-child{margin-left:auto}.lesson-heading{text-align:center;margin-top:10px}.lesson-heading>p{font-size:16px;color:var(--muted);margin-bottom:8px}.lesson-heading h1{font-size:38px;margin-bottom:25px}.stepper{list-style:none;display:flex;justify-content:center;margin:0 auto 26px;padding:0;gap:23px;max-width:860px}.stepper li{display:flex;align-items:center;gap:8px;color:#506459;font-size:16px;line-height:1.2}.stepper li>span{width:30px;height:30px;background:#e7ebe1;border-radius:50%;display:grid;place-items:center;font-size:14px;font-weight:700;flex-shrink:0}.stepper .current{color:var(--ink);font-weight:800}.stepper .current>span{background:var(--green);color:white}.stepper .finished>span{background:#dceccc;color:var(--green)}.lesson-panel{max-width:960px;margin:auto;border:1.5px solid;border-radius:24px;padding:28px 36px;background:#fffefb}.phase-label{font-size:15px;text-transform:uppercase;letter-spacing:1.6px;color:var(--muted);font-weight:700;margin-bottom:12px}.question-heading{display:flex;align-items:flex-start;gap:18px}.question-heading h2{flex:1;font-size:28px;margin:0 0 10px}.speech-line{display:flex;align-items:flex-start;gap:14px}.speech-line p{flex:1}.instruction{color:var(--muted);font-size:19px;line-height:1.6}.speaker{display:grid;place-items:center;border:1px solid #a9bfaa;background:#fff;min-width:46px;width:46px;height:46px;border-radius:50%;flex-shrink:0}.speaker:hover{background:#edf5e7}.speaker svg{width:21px}.lesson-visual{display:flex;align-items:center;justify-content:center;min-height:125px;font-size:clamp(40px,6vw,72px);line-height:1.6;letter-spacing:8px;padding:14px;margin:14px 0 20px;border-radius:15px;background:#edf5e9}.interaction-help{font-size:15px;color:var(--muted);margin:8px 0 18px}.choices{display:grid;gap:12px;margin:14px 0 22px}.choice{display:flex;align-items:center;text-align:left;gap:12px;border:2px solid #d4ded0;border-radius:15px;background:#fff;padding:16px 20px;font-size:20px;min-height:62px}.choice.selected{border-color:var(--green);background:#edf6e6}.choice:hover:not(:disabled){border-color:#7e9c7b}.choice-tick{margin-left:auto;min-width:20px;color:var(--green);font-size:24px}.image-choices{grid-template-columns:repeat(3,1fr)}.image-choices .choice{flex-direction:column;text-align:center;padding:20px 10px;font-size:19px;gap:9px}.choice-picture{font-size:54px;line-height:1.5}.image-choices .choice-tick{margin:0;height:24px}.check{margin:4px 0 12px}.feedback{padding:15px 18px;border-radius:12px;border:1px solid #dec48a;background:#fff6da;color:#60441c;font-size:18px;margin:8px 0 20px}.feedback.success{border-color:#a5c795;background:#edf8e4;color:var(--ink)}.lesson-bottom{margin-top:26px;padding-top:20px;border-top:1px solid var(--line);display:flex;align-items:center;justify-content:space-between;gap:16px}.vocab-row{display:flex;flex-wrap:wrap;align-items:center;gap:8px;font-size:15px;max-width:60%}.vocab-row>span{width:100%;color:var(--muted)}.vocab-word{display:flex;align-items:center;gap:5px}.word-button{min-height:46px;padding:8px 12px;border-radius:10px;background:#ecf3e6;text-decoration:underline;text-underline-offset:3px}.vocab-word .speaker{width:44px;min-width:44px;height:44px}.next{flex-shrink:0}.save-note{text-align:center;font-size:14px;color:var(--muted);margin:18px 0 22px}.sort-pool{display:flex;flex-wrap:wrap;gap:10px;min-height:58px;margin:12px 0 18px}.sort-item{padding:10px 15px;border:2px solid #b5c5ae;border-radius:12px;background:#fff;font-size:18px;cursor:grab}.sort-item.selected{background:#edf6e6;border-color:var(--green)}.sort-groups{display:grid;grid-template-columns:repeat(2,1fr);gap:14px;margin-bottom:20px}.sort-group{border:2px dashed #a1b797;border-radius:14px;min-height:180px;padding:12px}.group-target{width:100%;text-align:left;font-size:19px;font-weight:700;padding:6px 10px;background:#edf3e8;border-radius:8px;min-height:48px}.group-target span{float:right}.placed-items{display:flex;flex-wrap:wrap;gap:8px;padding-top:12px}.sequence{list-style:none;padding:0;margin:16px 0;display:grid;gap:10px}.sequence li{display:flex;align-items:center;gap:14px;border:1px solid #b9cab0;background:#fff;padding:10px 15px;border-radius:13px;cursor:grab}.stage-number{display:grid;place-items:center;border-radius:50%;background:#ebf3e3;width:34px;height:34px;flex-shrink:0;font-size:17px}.stage-label{flex:1;font-size:20px}.move-buttons{display:flex;gap:8px}.move-buttons button{height:46px;width:46px;border:1px solid #a5b59e;background:#f5f8ef;border-radius:10px;font-size:24px}.matching{display:grid;gap:12px;margin:18px 0}.match-row{display:grid;grid-template-columns:1fr 1.2fr;align-items:center;gap:18px}.match-row label{font-weight:700;font-size:18px}select{border:2px solid #b9cbb0;background:white;padding:10px 12px;border-radius:12px;width:100%;font-size:18px}.sentence-output{padding:19px;border:2px dashed #a1b49a;background:#f4f8ef;border-radius:14px;min-height:90px;font-size:23px;line-height:1.6;margin:18px 0}.sentence-blocks{display:flex;flex-wrap:wrap;gap:10px}.sentence-blocks button{padding:12px 18px;border:2px solid #b4c8a7;background:#fff;border-radius:12px;font-size:19px;text-align:left}.builder-tools{display:flex;gap:20px;margin:12px 0}.scaffold{border:0;padding:0;margin:12px 0 20px;display:flex;flex-wrap:wrap;gap:9px}.scaffold legend{font-size:16px;color:var(--muted);margin-bottom:10px}.scaffold button{font-size:15px;padding:10px 14px;border:1px solid #b5c3ab;border-radius:10px;background:#fff}.scaffold button.active{background:var(--green);color:white;border-color:var(--green)}.partial-prompt{font-size:24px;font-weight:700;padding:18px 20px;background:#eef5e7;border-radius:12px}.partial-prompt span{letter-spacing:1px}textarea{width:100%;border:2px solid #a7bd9c;border-radius:13px;background:#fff;padding:14px;resize:vertical;font-size:20px;line-height:1.5;display:block;margin-top:9px}.model,.observation{padding:18px 20px;border-radius:14px;background:#edf5e6;margin:18px 0}.model>p{font-size:17px}.compare-check{display:flex;align-items:center;gap:10px;font-size:17px}.compare-check input{width:24px;height:24px;min-height:24px;accent-color:var(--green);flex-shrink:0}.completion{text-align:center;max-width:850px;margin:70px auto}.completion h1{font-size:45px}.completion>p{font-size:22px;color:var(--muted)}.celebration{font-size:100px;line-height:1.5;animation:pop .8s ease}.earned-star{font-size:20px;background:#fbf2cd;border:1px solid #e3cf85;border-radius:15px;padding:15px;display:inline-block;margin:15px 0}.completion-actions{display:flex;flex-wrap:wrap;justify-content:center;gap:15px;margin:25px 0}.completion-actions>.text-button{flex-basis:100%;justify-content:center}.world-badge{font-size:26px;background:#edf5e5;padding:22px;border-radius:18px;margin:18px auto;max-width:650px}.world-badge span{font-size:17px}.storage-status{padding:10px 20px;background:#fff3d5;font-size:15px;text-align:center}dialog{border:1px solid #b6c9ab;border-radius:22px;padding:30px;max-width:540px;width:calc(100% - 36px);background:var(--paper);color:var(--ink)}dialog::backdrop{background:#123d2f65;backdrop-filter:blur(3px)}dialog h2{font-size:29px}dialog p{font-size:18px}dialog .primary,dialog .secondary{margin:16px 8px 0 0}.chinese-help{margin:20px 0;font-size:18px}.chinese-help summary{cursor:pointer;min-height:48px;padding:10px 14px;border:1px solid #b5c8ab;border-radius:12px;width:max-content;background:#eef5e8}.chinese-help p{margin:16px 0}.toast{position:fixed;bottom:20px;left:50%;transform:translateX(-50%);width:max-content;max-width:calc(100% - 32px);background:#234f3d;color:white;padding:14px 20px;z-index:8;border-radius:14px;box-shadow:0 6px 20px #0002;font-size:17px;pointer-events:none}[hidden]{display:none!important}@keyframes pop{0%{transform:scale(.6) rotate(-12deg);opacity:0}65%{transform:scale(1.12) rotate(8deg)}100%{transform:scale(1);opacity:1}}@media(min-width:1400px){.welcome{min-height:275px}.hero-art{width:315px;height:315px}.world-card{min-height:218px}.world-card .art{width:200px;height:200px}.discovery-note{margin-top:30px}}
@media(max-width:1100px){main{padding:0 26px}.welcome{min-height:235px;padding-left:10px}.welcome h1{font-size:47px}.hero-art{width:240px;height:240px;right:-10px}.world-card{padding-right:45px;min-height:200px}.world-card .art{width:130px;height:160px;background-size:300% 200%}.world-info h3{font-size:25px}.world-info>p{font-size:17px}.world-progress{font-size:15px}.world-arrow{width:40px;height:40px;right:14px;bottom:19px}.world-arrow svg{width:22px}.world-picker>h2{font-size:29px;margin-left:10px}.intro{margin-left:10px;font-size:20px}.world-card .art{height:130px}.stepper{gap:16px}.lesson-panel{padding:25px 28px}}
@media(max-width:760px){body{font-size:18px}.topbar{height:68px;padding:0 20px}.top-tools{gap:15px;font-size:17px}.icon-button{padding-left:15px;min-width:45px}.brand{font-size:19px;gap:8px}.brand span{font-size:27px}main{padding:0 20px}.welcome{min-height:215px;padding:28px 0}.welcome h1{font-size:39px;max-width:500px}.welcome>div{max-width:calc(100% - 145px)}.subtitle{font-size:24px}.hero-art{width:185px;height:185px;top:20px;right:-10px}.world-grid{grid-template-columns:1fr;gap:13px}.world-picker>h2{font-size:27px;margin-left:0}.intro{margin-left:0;font-size:18px}.world-card{min-height:184px;padding:15px 60px 15px 8px}.world-card .art{width:155px;height:155px}.world-info h3{font-size:28px}.world-info>p{font-size:18px;min-height:0;margin-bottom:18px}.world-arrow{width:44px;height:44px;right:18px;bottom:22px}.discovery-note{align-items:flex-start;font-size:16px;margin-top:25px}.discovery-note strong{font-size:18px}.resume-row{display:block}.resume-row>span{display:block}.world-heading{padding:0}.world-heading h1{font-size:34px}.world-heading .art{width:130px;height:130px}.world-heading .subtitle{font-size:21px}.world-heading p:last-child{font-size:15px}.lesson-heading h1{font-size:31px}.stepper{gap:7px;justify-content:space-between}.stepper li{flex-direction:column;gap:6px;font-size:12px}.stepper li>span{width:28px;height:28px}.lesson-panel{padding:22px 20px}.question-heading h2{font-size:25px}.lesson-bottom{flex-direction:column;align-items:stretch}.vocab-row{max-width:100%}.next{align-self:stretch}.match-row{grid-template-columns:1fr;gap:6px;border-bottom:1px solid var(--line);padding-bottom:12px}.completion{margin:50px auto}.completion h1{font-size:34px}.sort-item{font-size:16px}.group-target{font-size:17px}.stage-label{font-size:18px}.sequence li{padding:10px}.move-buttons{gap:5px}.move-buttons button{width:44px}.image-choices .choice{font-size:16px}.choice-picture{font-size:44px}.activity-row{padding:14px;gap:13px}.activity-row h2{font-size:20px}.completion-actions{flex-direction:column}.builder-tools{gap:12px}}
@media(max-width:430px){main{padding:0 16px}.topbar{padding:0 16px}.brand{font-size:17px}.top-tools{gap:12px;font-size:15px}#stars span{font-size:23px}.welcome{min-height:190px;align-items:flex-start}.welcome>div{max-width:75%}.welcome h1{font-size:35px;line-height:1.15;letter-spacing:-1.2px;max-width:265px}.welcome .subtitle{font-size:20px;max-width:230px}.hero-art{width:127px;height:127px;top:48px;right:-6px}.world-picker>h2{font-size:25px}.world-card .art{width:115px;height:115px}.world-card{padding-left:4px;padding-right:47px;min-height:173px}.world-info h3{font-size:23px;letter-spacing:-.4px}.world-info>p{font-size:16px;margin-bottom:14px;min-height:43px}.world-progress{font-size:14px}.world-arrow{width:36px;height:36px;right:10px;bottom:18px}.world-arrow svg{width:19px}.world-heading .art{display:none}.lesson-panel{padding:20px 16px}.question-heading{gap:9px}.question-heading h2{font-size:23px}.speech-line{gap:9px}.instruction{font-size:17px}.choice{font-size:18px;padding:14px}.image-choices{gap:7px}.image-choices .choice{padding:12px 6px;font-size:15px}.choice-picture{font-size:36px}.sort-groups{gap:8px}.sort-group{padding:8px}.group-target{font-size:15px;padding:6px}.sort-item{font-size:15px;padding:8px}.stage-number{width:26px;height:26px;font-size:15px}.sequence li{gap:8px;padding:8px}.stage-label{font-size:16px}.move-buttons button{width:44px;font-size:22px}.sentence-blocks button{font-size:18px;padding:10px 13px}.sentence-output{font-size:20px}.scaffold button{font-size:14px;padding:10px}.back-link{font-size:16px}.discovery-note{gap:12px}.discovery-note>span{font-size:35px}}
@media(prefers-reduced-motion:reduce){*,*::before,*::after{animation:none!important;transition:none!important;scroll-behavior:auto!important}}
h1,h2,h3,.brand{font-family:ui-rounded,'Arial Rounded MT Bold','Trebuchet MS',Arial,sans-serif}
.sort-item[draggable="true"],.sequence li[draggable="true"]{-webkit-user-drag:element;user-select:none}
.sort-item{display:inline-flex;align-items:center;padding:0 9px 0 4px!important}.sort-select{padding:10px 7px;font-size:inherit;border:0;background:transparent;min-height:46px;-webkit-user-drag:none}.drag-handle{display:grid;place-items:center;width:22px;height:46px;cursor:grab}.drag-handle svg{width:16px;height:24px;fill:#6b8963;stroke:none}
.drag-handle{touch-action:none;-webkit-user-drag:none}.dragging{background:#e5f4d8;box-shadow:0 0 0 3px #20573f33}.dragging .drag-handle{cursor:grabbing}
.sort-item{max-width:100%;min-width:0}.sort-select{min-width:0;overflow-wrap:anywhere}.drag-handle{flex-shrink:0}
@media(min-width:1101px){.discovery-note{margin:20px 0 0}footer{padding:8px 20px 12px}}
@media(min-width:1101px){main{max-width:1400px}.welcome{min-height:237px}.welcome h1{font-size:76px}.welcome .subtitle{font-size:38px}.hero-art{width:310px;height:310px;top:-5px;right:-10px}.welcome>div{max-width:calc(100% - 290px)}.world-picker>h2{font-size:38px}.world-picker>.intro{font-size:25px}.world-card{min-height:232px}.world-card .art{width:195px;height:195px}.world-info h3{font-size:36px}.world-info>p{font-size:22px}.world-progress{font-size:19px}.world-arrow{width:54px;height:54px}.discovery-note{font-size:20px}.discovery-note strong{font-size:23px}}

/* V0.2 bilingual hierarchy: English leads; the paired Chinese line sits directly below. */
.en{display:block;min-width:0;overflow-wrap:anywhere}
.zh{display:block;min-width:0;margin-top:.12em;color:#315344;font-size:max(.86em,16px);font-weight:500;line-height:1.38;overflow-wrap:anywhere}
body[data-language="english"] .zh{display:none!important}
h1 .zh{font-size:clamp(19px,.47em,28px);font-weight:600;letter-spacing:0;margin-top:.2em}
h2 .zh,h3 .zh{font-size:clamp(18px,.65em,22px);font-weight:600;letter-spacing:0}
.subtitle .zh{font-size:.72em;font-weight:500}
button .zh,a .zh{font-size:max(.82em,16px)}
.stepper .zh,.phase-label .zh,.world-progress .zh,.activity-number .zh{font-size:15px}
.choice{min-width:0;align-items:flex-start}.choice>.en,.choice>.zh{flex:1;min-width:0}.choice-tick{margin-left:auto}
.image-choices .choice{align-items:center;flex-wrap:wrap}.image-choices .choice>span:not(.choice-picture):not(.choice-tick){min-width:0;flex:1}
.image-choices .choice>span .en,.image-choices .choice>span .zh{display:block}
.speech-line p{min-width:0}.sentence-output .en{font-weight:700}.sentence-output .zh{font-weight:500}
.word-button{text-align:left}.word-button .en{font-weight:700}.word-button .zh{font-size:15px}
.language-switch{border:1px solid #a9beb0;border-radius:9px;padding:5px 9px;min-height:40px;background:#f4f8f1;color:#174e3c;font-size:14px;font-weight:700;white-space:nowrap}
.language-switch[aria-pressed="true"]{background:#e7efe7}.language-switch:hover{background:#dcebdd}
#stars>.en,#stars>.zh{display:block}
#stars .en,#stars .zh{font-size:14px;line-height:1.15}
.vocab-row{flex-wrap:wrap}
.vocabulary{max-width:420px;max-height:min(75vh,560px);overflow-y:auto;box-shadow:0 8px 24px #0002}
.vocabulary h2{font-size:27px}.vocabulary h2 .zh{font-size:20px}
.vocabulary .word-detail{margin:12px 0 18px}.vocabulary .word-detail strong{display:block;margin-top:10px}.vocabulary .word-detail p{margin:4px 0 8px}
.vocabulary .speaker{margin-right:12px}
.match-row label .zh{font-size:16px}
.sort-select .en,.sort-select .zh,.group-target .en,.group-target .zh,.stage-label .en,.stage-label .zh{display:block}
@media(max-width:700px){
  .topbar{padding:0 14px;gap:8px}.top-tools{gap:8px}.brand{gap:5px;font-size:17px}.brand span{font-size:22px}
  #stars{gap:4px;font-size:13px;line-height:1.15}#stars span{font-size:13px}#stars>span:first-child{font-size:19px}
  .icon-button{min-width:39px;padding-left:8px}.icon-button svg{width:22px;height:22px}.language-switch{font-size:12px;padding:4px 6px}
  .stepper li{min-width:0}.stepper .zh{font-size:13px}
  .world-card .zh{font-size:16px}.world-info>p{min-height:0}
  .choice .zh,.sort-select .zh,.group-target .zh{font-size:16px}
  .vocabulary{max-height:65vh}
}
@media(max-width:700px){
  .brand{white-space:nowrap;flex-shrink:0;font-size:15px;letter-spacing:-.2px}
  .top-tools{flex-shrink:0}
  #stars{min-width:48px;white-space:nowrap;gap:3px}
  #stars .en,#stars .zh{font-size:11px;white-space:nowrap;overflow-wrap:normal}
  .language-switch{white-space:nowrap}
}
@media(max-width:700px){#stars{min-width:30px;font-size:16px}#stars .en,#stars .zh{display:none}}
.stepper .step-label{min-width:0;text-align:center}
.stepper .step-label .en,.stepper .step-label .zh{display:block;overflow-wrap:normal;word-break:normal}
@media(max-width:700px){
  .stepper{justify-content:flex-start;overflow-x:auto;scrollbar-width:none;gap:6px;padding-bottom:5px}
  .stepper::-webkit-scrollbar{display:none}
  .stepper li{flex:0 0 73px;font-size:14px}
  .stepper .step-label .en{font-size:14px;white-space:nowrap}
  .stepper .step-label .zh{font-size:14px;white-space:nowrap}
}
@media(max-width:700px){
  .stepper{justify-content:space-around;overflow:visible;gap:6px;margin-bottom:18px}
  .stepper li{flex:0 0 auto}
  .stepper .step-label{display:none}
}
.choice-label{flex:1;min-width:0;text-align:left}
.choice-label .en,.choice-label .zh{display:block}
.bilingual-label{display:block;min-width:0}
.group-target{display:flex;align-items:center;gap:4px}
.group-target span{float:none}
.group-target>.bilingual-label{flex:1;text-align:left}
.group-target>.bilingual-label .en,.group-target>.bilingual-label .zh{display:block}
.primary .zh{color:#e9f5ea}
.primary:disabled .zh{color:#f5faf5}

/* V0.3 optional Science Challenge Lab: the four core world cards stay unchanged. */
.challenge-home-card{display:flex;align-items:center;gap:18px;margin:22px 0 8px;padding:20px 24px;border:2px solid #91c4bc;border-radius:20px;background:#eaf7f5;min-height:122px}
.challenge-home-card:hover{background:#dff1ee}
.challenge-icon{font-size:46px;line-height:1;flex-shrink:0}
.challenge-home-copy{display:grid;gap:5px;flex:1;min-width:0}
.challenge-home-copy strong{font-size:25px;line-height:1.2}
.challenge-home-copy>span:nth-child(2){font-size:17px}
.challenge-home-copy small{font-size:14px;color:#23584d;font-weight:700}
.challenge-home-count{display:grid;gap:4px;font-size:15px;text-align:right;color:#23584d}
.challenge-home-count b{font-size:25px;color:#123d2f}
.challenge-heading{display:flex;align-items:center;gap:22px;margin:28px 0 24px;padding:22px 24px;border-radius:20px;background:#eaf7f5;border:1px solid #91c4bc}
.challenge-heading h1{font-size:clamp(32px,4vw,48px);margin:0 0 8px}
.challenge-heading p{margin:0 0 6px;font-size:18px}
.challenge-optional{font-weight:700;color:#23584d}
.challenge-collections{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}
.challenge-collection{padding:22px;border:1px solid var(--line);border-radius:18px;background:#fff}
.challenge-collection h2{font-size:27px;margin-bottom:8px}
.challenge-collection>p{font-size:17px;margin-bottom:8px}
.challenge-progress{font-weight:700;color:var(--green)}
.challenge-activity-list{display:grid;gap:8px;margin-top:15px}
.challenge-activity-list a{display:flex;align-items:center;gap:12px;padding:12px;border-radius:11px;background:#f3f8f5;min-height:55px}
.challenge-activity-list a:hover{background:#e8f3ed}
.challenge-activity-list a>span:first-child{width:25px;text-align:center;color:var(--green);font-weight:800}
.challenge-activity-list a>strong{flex:1;min-width:0;font-size:17px}
.challenge-journal-link{margin:25px 0;display:inline-flex}
.challenge-lesson-heading{margin:25px auto 18px;max-width:950px}
.challenge-lesson-heading>p:first-child{font-size:17px;font-weight:700;color:var(--green)}
.challenge-lesson-heading h1{font-size:clamp(32px,4vw,48px);margin-bottom:10px}
.challenge-lesson-heading>p:last-child{font-size:19px;color:var(--muted)}
.challenge-observe,.challenge-work{max-width:950px;margin:16px auto;padding:24px;border-radius:20px;border:1px solid #adc9bf;background:#f4faf8}
.challenge-work{background:#fff;border-color:var(--line)}
.challenge-observe h2,.challenge-work h2{font-size:27px}
.challenge-observe>p,.challenge-work>p{font-size:18px}
.challenge-table-wrap{width:100%;overflow-x:auto;margin:16px 0}
.challenge-table{width:100%;border-collapse:collapse;background:#fff;border:1px solid #b6cfc5;font-size:18px}
.challenge-table th,.challenge-table td{padding:11px 13px;border:1px solid #c9dbd2;text-align:left;vertical-align:top}
.challenge-table th{background:#e3f1e9}
.challenge-table .zh{font-size:16px}
.challenge-sort,.challenge-trials,.challenge-sequence{display:grid;gap:12px;margin:16px 0}
.challenge-sort-row,.challenge-trial,.challenge-sequence li{padding:14px;border:1px solid #c4d7cb;border-radius:12px;background:#f7fbf8}
.challenge-sort-row strong{display:block;margin-bottom:9px}
.challenge-sort-row>div{display:flex;flex-wrap:wrap;gap:7px}
.challenge-sort-row button,.challenge-scaffold button{padding:10px 13px;border:1px solid #a6c2b2;border-radius:10px;background:white;min-height:48px;text-align:left}
.challenge-sort-row button[aria-pressed="true"],.challenge-scaffold button[aria-pressed="true"]{background:#20573f;color:#fff;border-color:#20573f}
.challenge-sort-row button[aria-pressed="true"] .zh,.challenge-scaffold button[aria-pressed="true"] .zh{color:#e9f5ea}
.challenge-sequence{list-style:none;padding:0}
.challenge-sequence li{display:flex;align-items:center;gap:12px}
.challenge-sequence li>span{flex:1}
.challenge-sequence li>div{display:flex;gap:6px}
.challenge-sequence button{width:46px;height:46px;border:1px solid #a6c2b2;border-radius:9px;background:#fff}
.challenge-sequence button:disabled{opacity:.4}
.challenge-trial p{margin-bottom:9px}
.challenge-trial strong{display:block;color:var(--green)}
.challenge-task-check{margin-top:8px}
.challenge-hints{margin:20px 0}
.challenge-hints button{margin-bottom:8px}
.challenge-hints p{padding:9px 12px;margin:6px 0;border-left:3px solid #82b1a2;background:#f2f8f4;font-size:17px}
.challenge-scaffold{display:grid;gap:16px;margin:22px 0}
.challenge-scaffold fieldset{border:1px solid #bdd5c5;border-radius:14px;padding:15px;min-width:0}
.challenge-scaffold legend{font-weight:800;padding:0 7px}
.challenge-scaffold fieldset>div{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:9px}
.challenge-scaffold button .en{font-weight:700}
.challenge-scaffold button .zh{font-size:16px}
.challenge-model{margin-top:20px;padding:20px;border-radius:14px;background:#eaf5eb;border:1px solid #bad0bd}
.challenge-model h2{font-size:25px}
.challenge-model p{font-size:19px}
.challenge-model .speaker{margin:7px 0}
.challenge-saved{color:var(--green);font-weight:700}
.challenge-vocab{max-width:950px;margin:15px auto 35px;display:flex;align-items:center;flex-wrap:wrap;gap:9px}
.challenge-vocab>span{font-weight:700;font-size:17px}
.challenge-vocab button{padding:8px 12px;border:1px solid #b6cbbc;border-radius:10px;background:white;text-align:left}
.virtual-scene{display:flex;align-items:center;justify-content:center;gap:20px;margin:15px auto;padding:18px;background:#fff;border:1px solid #b6cfc5;border-radius:15px;min-height:160px}
.compass-scene{position:relative;max-width:300px}
.compass-scene>span:not(.bar-magnet){position:absolute;font-weight:800;color:#20573f}
.compass-n{top:8px}.compass-s{bottom:8px}.compass-e{right:12px}.compass-w{left:12px}
.bar-magnet{display:flex;width:115px;height:42px;transform:rotate(35deg);transition:transform .65s ease;border:2px solid #35594a;border-radius:8px;overflow:hidden;text-align:center}
.bar-magnet.settled{transform:rotate(90deg)}
.bar-magnet b{width:50%;display:grid;place-items:center;background:#d8e9eb}
.bar-magnet b:first-child{background:#f5d9ce}
.coil-scene{font-size:37px}.coil-wire{font-size:38px;color:#668777}.coil-wire.powered{color:#20573f}
.journal-list{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:15px;margin-bottom:30px}
.journal-entry{padding:20px;border:1px solid #bdd5c5;border-radius:16px;background:#fff}
.journal-entry h2{font-size:24px}.journal-entry p{font-size:15px;color:var(--muted)}
.journal-entry>div{display:grid;margin:10px 0;gap:4px}.journal-entry>div strong{font-size:16px}
.journal-entry>a{text-decoration:underline;color:var(--green)}
.challenge-empty{font-size:18px;margin:25px 0}
@media(max-width:700px){
  .challenge-home-card{padding:16px;gap:10px;align-items:flex-start;flex-wrap:wrap}.challenge-icon{font-size:35px}
  .challenge-home-copy{flex-basis:calc(100% - 55px)}.challenge-home-copy strong{font-size:21px}
  .challenge-home-count{width:100%;display:flex;justify-content:space-between;align-items:center;text-align:left;border-top:1px solid #b9d8cb;padding-top:8px}
  .challenge-home-count b{font-size:21px}
  .challenge-collections,.journal-list{grid-template-columns:1fr}
  .challenge-heading{padding:18px;gap:12px}.challenge-heading h1{font-size:32px}
  .challenge-observe,.challenge-work{padding:17px;margin:14px 0}
  .challenge-scaffold fieldset>div{grid-template-columns:1fr}
  .challenge-table,.challenge-table tbody,.challenge-table tr,.challenge-table td{display:block;width:100%}
  .challenge-table thead{display:none}
  .challenge-table tr{margin:10px 0;border:1px solid #bed4c6;border-radius:11px;overflow:hidden;background:#fff}
  .challenge-table td{border:0;border-bottom:1px solid #e2eee6;padding:9px 12px}
  .challenge-table td:last-child{border-bottom:0}
  .challenge-table td::before{content:attr(data-label);display:block;font-size:14px;font-weight:800;color:#315344}
}

/* Learning Loop: native cream cards, gentle feedback, one review at a time. */
.learning-home-card{display:flex;align-items:center;justify-content:space-between;gap:24px;padding:26px 30px;margin:10px 0 14px;background:#edf3e8;border:1px solid #b7c8b4;border-radius:18px}
.learning-home-card h2{margin:0 0 10px}.learning-home-card p{margin:6px 0}.learning-home-card .primary{flex-shrink:0}
.learning-links{display:flex;flex-wrap:wrap;gap:16px 28px;margin-bottom:34px}.learning-links a{min-height:44px;display:inline-flex;align-items:center;font-weight:700;color:#174e3c}
.learning-domain-grid{display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px;margin:24px 0 32px}
.learning-domain,.learning-mistake,.learning-practice{background:#fffdf7;border:1px solid #d5dcca;border-radius:16px;padding:24px;min-width:0}
.learning-domain h2{font-size:24px;margin:0 0 18px}.learning-badge{display:inline-block;padding:7px 12px;border-radius:10px;background:#edf3e8;color:#174e3c;font-weight:700}
.learning-mistakes{display:grid;gap:22px;margin:24px 0}.learning-mistake h2{font-size:24px}.learning-mistake dt{font-weight:700;margin-top:20px}.learning-mistake dd{margin:8px 0 0;overflow-wrap:anywhere}.learning-mistake .secondary{margin-top:24px}
.learning-practice-row{display:flex;align-items:center;justify-content:space-between;gap:18px;padding:18px 0;border-bottom:1px solid #dfe4d6}.learning-practice-row:last-child{border-bottom:0}.learning-practice-row .secondary{flex-shrink:0}
.learning-review{margin-top:20px}.learning-review .challenge-observe{padding:20px;margin:18px 0}.learning-review .challenge-scaffold{margin:16px 0}.learning-review .feedback{background:#eff3e6;border-color:#c0ceb7;color:#174e3c}
.learning-hints{margin:22px 0}.learning-hints p{margin:16px 0;padding:16px;background:#f4f5e9;border-radius:12px}.learning-result:not(:empty){border-top:1px solid #ced9c4;margin-top:22px;padding-top:20px}.learning-outcome{font-weight:800;color:#174e3c;font-size:21px}.learning-result .primary,.learning-result .secondary{margin:12px 12px 0 0}
.learning-finish{max-width:760px;margin:24px auto;padding:28px;background:#fffdf7;border-radius:18px;border:1px solid #d5dcca}.learning-empty{padding:24px;background:#edf3e8;border-radius:14px}
.learning-review .challenge-table{min-width:0;width:100%;table-layout:fixed}.learning-review .challenge-table th,.learning-review .challenge-table td{overflow-wrap:anywhere}
@media(max-width:700px){.learning-home-card{align-items:flex-start;flex-direction:column;padding:22px}.learning-home-card .primary{width:100%;text-align:center}.learning-domain-grid{grid-template-columns:1fr}.learning-domain,.learning-mistake,.learning-practice{padding:20px}.learning-practice-row{align-items:flex-start;flex-direction:column}.learning-review .challenge-observe{padding:14px}.learning-links{gap:14px 22px}.learning-finish{padding:22px}}
.learning-cell-label{display:none}
@media(max-width:700px){.learning-review .challenge-table td::before{display:none}.learning-cell-label{display:block;font-weight:800;margin-bottom:6px;font-size:16px}.learning-cell-label .zh{font-size:16px}}