:root{--ink:#253e38;--muted:#61766e;--green:#246d54;--green-dark:#18543f;--mint:#e8f2ea;--paper:#f6f7f2;--line:#e2e8de;--gold:#f3c064;--orange:#b15d23;--white:#fff;--radius:24px;font-family:ui-rounded,"PingFang SC","Microsoft YaHei",system-ui,sans-serif;color:var(--ink);background:var(--paper);font-synthesis:none}
*{box-sizing:border-box}body{margin:0}button,input{font:inherit}button{cursor:pointer;border:0;touch-action:manipulation;-webkit-tap-highlight-color:transparent}button:disabled{cursor:default;opacity:.48}button:focus-visible,a:focus-visible,input:focus-visible,summary:focus-visible{outline:3px solid #bc6d22;outline-offset:4px}button{transition:background .15s,transform .15s}button:active:not(:disabled){transform:translateY(1px)}[hidden]{display:none!important}a{color:inherit}.app-shell{max-width:1280px;margin:auto;padding:0 36px calc(12px + env(safe-area-inset-bottom))}.topbar{min-height:90px;display:flex;align-items:center;justify-content:space-between;gap:20px;border-bottom:1px solid var(--line)}.brand{display:flex;align-items:center;gap:11px;text-decoration:none;font-size:22px;font-weight:800;letter-spacing:-.6px}.brand small{display:block;font-size:11px;color:var(--muted);font-weight:500;letter-spacing:2px;margin-top:2px}.brand-mark{display:flex;align-items:center;justify-content:center;position:relative;width:42px;height:46px;background:var(--green);color:#fff;border-radius:14px 14px 14px 4px;font-size:35px;line-height:1;font-family:Georgia,serif}.brand-mark span{position:absolute;top:4px;right:4px;font-size:16px;color:var(--gold)}.grade-tag{background:#edf0e8;color:#506452;border:1px solid var(--line);border-radius:99px;padding:9px 17px;font-size:13px;white-space:nowrap}.grade-tag span{padding:0 8px;color:#96a08d}.account{display:flex;align-items:center;gap:10px;font-size:14px}.avatar{display:grid;place-items:center;background:#f3dfb8;border-radius:50%;width:34px;height:34px;font-size:25px;color:#7e5727}.text-button{background:transparent;color:var(--muted);font-size:13px;min-height:44px;padding:8px 10px;border-radius:10px}.text-button:hover{background:var(--mint);color:var(--green)}.intro{display:flex;align-items:center;justify-content:space-between;gap:20px;padding:27px 0 23px}.eyebrow{font-size:11px;letter-spacing:2px;color:var(--green);font-weight:700;margin:0 0 9px}h1{font-size:30px;letter-spacing:1px;line-height:1.3;margin:0 0 8px}.intro p:not(.eyebrow){font-size:14px;color:var(--muted);margin:0}.progress-summary{font-size:12px;line-height:1.9;text-align:right;color:var(--muted);max-width:300px}.progress-summary strong{color:var(--green);font-size:22px;padding:0 4px}.practice-settings{display:flex;align-items:center;gap:22px;background:#fff;border:1px solid var(--line);border-radius:18px;padding:13px 16px;margin-bottom:20px}.settings-block{display:flex;align-items:center;gap:12px}.settings-label{font-size:12px;color:var(--muted);white-space:nowrap}.segmented{display:flex;padding:4px;gap:3px;background:#f3f5ef;border-radius:12px}.segmented button{padding:0 17px;min-height:44px;white-space:nowrap;background:transparent;color:var(--muted);font-size:14px;border-radius:9px}.segmented button.selected{background:var(--green);color:white;font-weight:700;box-shadow:0 2px 3px #203d3420}.segmented.small button{padding:0 13px}.primary{background:var(--green);color:#fff;border-radius:12px;font-weight:700;min-height:52px;padding:12px 22px;display:flex;align-items:center;justify-content:center;gap:16px;font-size:16px}.primary:hover:not(:disabled){background:var(--green-dark)}.start-button{margin-left:auto;white-space:nowrap}.start-button span{font-size:22px;font-weight:400}.page-status{padding:12px 17px;margin-bottom:16px;background:#fff1d5;border:1px solid #edd09c;border-radius:12px;font-size:14px}.workspace{display:grid;grid-template-columns:1fr 1.04fr;gap:20px;align-items:stretch}.question-card,.guide-card{border-radius:var(--radius);border:1px solid var(--line);background:white;padding:22px 26px;min-width:0}.question-card{display:flex;flex-direction:column}.guide-card{background:#fcfbf6;border-color:#e8e4d8;display:flex;flex-direction:column}.card-top{display:flex;align-items:center;justify-content:space-between;gap:10px;min-height:30px}.section-tag{font-size:11px;font-weight:700;color:var(--green);background:var(--mint);padding:7px 11px;border-radius:7px;letter-spacing:1px}.section-tag.gold{background:#f5e8c9;color:#896029}.question-position{font-size:12px;color:var(--muted)}.lesson-options{display:flex;gap:6px;margin-top:10px}.lesson-options button{background:transparent;color:var(--muted);font-size:13px;min-height:44px;padding:7px 14px;border-radius:9px;border:1px solid transparent}.lesson-options button.selected{background:#f1f5ed;border-color:#dfe7d8;color:var(--green);font-weight:700}.question-card h2{font-size:16px;font-weight:500;text-align:center;margin:19px 0 18px}.equation{display:flex;align-items:center;justify-content:center;gap:16px;font-weight:800;font-size:48px;font-variant-numeric:tabular-nums;line-height:1.2;letter-spacing:-1px}.operator,.equals{font-size:32px;font-weight:500;color:#87988c}.equation input{width:87px;height:77px;border:2px dashed #adc2ad;border-radius:16px;background:#f2f6ee;text-align:center;color:var(--green);font-weight:800;font-size:42px;min-width:0;caret-color:transparent;padding:0;user-select:none}.equation input::placeholder{color:#9daf9a}.equation input.correct{border:2px solid var(--green);background:#e7f4e8}.equation input.incorrect{border:2px solid #c5803a;background:#fff4df}.answer-feedback{font-size:13px;text-align:center;min-height:38px;margin:12px 0 10px;line-height:1.5;color:var(--muted);display:grid;place-items:center}.answer-feedback.success{color:var(--green);font-weight:700}.answer-feedback.retry{color:#955921}.keypad{display:grid;grid-template-columns:repeat(3,1fr);gap:8px;width:100%;max-width:350px;margin:0 auto 13px}.keypad button{min-height:47px;background:#f3f5ef;border:1px solid #e8ece3;border-radius:10px;font-weight:650;font-size:23px;color:var(--ink)}.keypad button:hover:not(:disabled){background:#e6ede0}.keypad .utility{font-size:13px;color:var(--muted);font-weight:500}.check-button{width:100%;max-width:350px;margin:0 auto}.gentle-note{font-size:11px;color:var(--muted);text-align:center;line-height:1.6;margin:12px 0 0}.guide-card h2{font-size:23px;margin:14px 0 6px;letter-spacing:.5px}.guide-subtitle{font-size:13px;color:var(--muted);margin:0;line-height:1.6}.step-track{display:flex;gap:7px;margin:17px 0 17px}.step-track button{flex:1;height:44px;display:flex;align-items:center;justify-content:center;gap:6px;background:#edece3;color:#687362;border-radius:10px;font-size:12px}.step-track button.active{background:var(--green);color:#fff}.step-track .step-index{display:grid;place-items:center;flex-shrink:0;width:21px;height:21px;font-size:12px;border-radius:50%;background:#ffffff88;color:var(--green)}.step-track button.active .step-index{background:#ffffff24;color:#fff}.step-content{flex:1;min-height:232px}.step-title{display:flex;align-items:center;gap:9px;font-weight:700;font-size:16px;margin:0 0 10px}.step-title .step-bullet{color:var(--orange);font-size:13px;font-weight:800}.step-description{font-size:15px;line-height:1.8;margin:0 0 12px;min-height:54px}.math-line{text-align:center;font-size:26px;font-weight:750;letter-spacing:1px;line-height:1.5;background:#fff;border:1px solid #e9e4d6;border-radius:12px;padding:10px;margin:10px 0}.visual{background:#f2f0e5;border:1px solid #e5e2d5;border-radius:14px;padding:12px;min-height:110px}.visual-caption{font-size:12px;color:#566451;line-height:1.6;text-align:center;margin:8px 0 0}.frames{display:flex;flex-wrap:wrap;align-items:center;justify-content:center;gap:10px}.ten-frame{display:grid;grid-template-columns:repeat(5,19px);grid-template-rows:repeat(2,19px);gap:5px;padding:7px;border:1px solid #cbd4c0;border-radius:8px;background:#ffffff90}.bead{border:1px solid #d4dccb;background:transparent;border-radius:50%;width:19px;height:19px}.bead.green{background:var(--green);border-color:var(--green)}.bead.orange{background:#dea043;border-color:#b5762d}.bead.removed{background:#e4d3b1;border-color:#b49c75;position:relative}.bead.removed:after{content:"";position:absolute;width:19px;height:2px;top:8px;left:-1px;background:#886744;transform:rotate(-45deg)}.legend{display:flex;justify-content:center;gap:14px;font-size:11px;color:var(--muted);margin-top:9px;flex-wrap:wrap}.legend span{display:flex;align-items:center;gap:5px}.dot{width:8px;height:8px;border-radius:50%;display:inline-block;background:var(--green)}.dot.orange{background:#dea043}.place-value{display:grid;grid-template-columns:1fr 1fr;gap:8px}.place-cell{background:#ffffffb3;border:1px solid #e1decd;border-radius:10px;text-align:center;min-height:90px;padding:8px}.place-cell strong{display:block;font-size:12px;color:var(--muted);font-weight:500;margin-bottom:6px}.place-number{font-weight:800;font-size:28px;line-height:1.4}.place-number del{color:#99a58d;font-size:20px;font-weight:500;margin-right:8px}.place-number ins{text-decoration:none;color:var(--orange)}.ten-rods{display:flex;justify-content:center;gap:4px;flex-wrap:wrap}.ten-rod{display:grid;grid-template-columns:repeat(2,6px);grid-template-rows:repeat(5,6px);gap:2px;padding:4px;background:#ddebdc;border:1px solid #9cb795;border-radius:4px}.ten-rod i{width:6px;height:6px;background:var(--green);border-radius:1px}.loose-beads{display:flex;flex-wrap:wrap;gap:4px;justify-content:center;max-width:156px;margin:auto}.loose-beads .bead{width:14px;height:14px}.number-bond{display:flex;justify-content:center;align-items:center;gap:10px;font-size:22px;font-weight:700;flex-wrap:wrap;padding:12px 0}.number-chip{padding:9px 13px;border-radius:10px;background:#e0ecd9;color:var(--green)}.number-chip.orange{background:#f4dfb5;color:#945e24}.step-navigation{display:flex;align-items:center;justify-content:space-between;gap:8px;margin-top:16px}.secondary{min-height:44px;border:1px solid #d9dece;border-radius:9px;background:transparent;color:var(--muted);font-size:13px;padding:9px 14px}.secondary:hover:not(:disabled){background:#e8ebdf}.secondary.next-step{background:#e5eddf;border-color:#d4dfcd;color:var(--green);font-weight:700}.step-navigation>span{font-size:12px;color:var(--muted)}.remember{display:flex;align-items:flex-start;gap:11px;border-top:1px dashed #dcdccc;padding-top:14px;margin-top:17px}.remember-icon{color:#b98935;font-size:22px}.remember strong{font-size:12px}.remember p{font-size:12px;color:var(--muted);line-height:1.8;margin:4px 0 0}.all-steps{max-height:390px;overflow:auto;padding-right:8px}.all-steps ol{padding-left:25px;margin:5px 0}.all-steps li{font-size:14px;line-height:1.8;padding:0 0 15px 5px}.all-steps strong{font-size:15px;display:block}.all-steps .mini-math{display:block;color:var(--green);font-weight:750;font-size:19px;padding-top:4px}.question-progress{display:flex;gap:4px;padding-top:19px;padding-bottom:15px}.question-progress span{height:7px;flex:1;border-radius:5px;background:#e9ede4}.question-progress span.done{background:var(--green)}.question-progress span.current{background:var(--gold)}footer{display:flex;align-items:center;justify-content:center;gap:7px;font-size:11px;color:#798674;padding:18px 0 4px}.footer-dot{height:5px;width:5px;border-radius:50%;background:#9cae88}.footer-extra{margin-left:6px}.result-card{max-width:850px;margin:auto;border:1px solid var(--line);background:white;border-radius:24px;padding:30px;text-align:center}.result-star{color:#be8c33;font-size:42px}.result-card h2{font-size:27px;margin:9px 0}.result-card p{color:var(--muted);line-height:1.7;font-size:15px}.result-numbers{display:flex;justify-content:center;gap:32px;margin:25px 0}.result-numbers strong{display:block;color:var(--green);font-size:38px}.result-numbers span{font-size:12px;color:var(--muted)}.result-actions{display:flex;gap:12px;justify-content:center;flex-wrap:wrap}.review-list{text-align:left;margin-top:26px;border-top:1px solid var(--line);padding-top:10px}.review-list h3{font-size:17px}.review-list details{padding:8px 0;border-bottom:1px solid var(--line)}.review-list summary{cursor:pointer;font-size:16px;min-height:44px;line-height:1.7;padding:9px 3px;color:var(--green)}.review-list small{font-size:12px;color:var(--muted);margin-left:10px}.review-list ol{text-align:left;font-size:14px;line-height:1.8;padding-left:23px}.review-list li{margin-bottom:10px}.review-list li strong{display:block}.save-message{font-size:12px!important;margin-top:20px}.review-label{display:inline-block;margin-bottom:13px;color:var(--green);background:var(--mint);padding:8px 13px;border-radius:10px;font-size:13px}
@media(min-width:1024px) and (max-height:850px){.topbar{min-height:70px}.intro{padding:18px 0}.intro h1{font-size:27px}.practice-settings{margin-bottom:16px;padding:10px 14px}.question-card,.guide-card{padding:16px 23px}.question-card h2{margin:12px 0}.equation{font-size:44px}.equation input{height:67px;width:78px;font-size:37px}.keypad{gap:6px;margin-bottom:10px}.keypad button{min-height:44px}.answer-feedback{margin:9px 0 6px;min-height:30px}.step-content{min-height:217px}.guide-card h2{font-size:21px;margin-top:11px}.step-track{margin:12px 0}.step-description{min-height:45px;font-size:14px}.step-navigation{margin-top:10px}.remember{margin-top:12px;padding-top:10px}.gentle-note{margin-top:9px}footer{padding-top:13px}}
@media(max-width:1050px){.app-shell{padding-left:24px;padding-right:24px}.practice-settings{gap:12px}.settings-label{display:none}.segmented button{padding:0 14px}.question-card,.guide-card{padding-left:20px;padding-right:20px}.equation{gap:13px}.step-track button{font-size:11px;gap:4px}.step-track .step-index{width:18px;height:18px}.grade-tag{font-size:12px}}
@media(min-width:720px) and (max-width:900px){.app-shell{padding-left:20px;padding-right:20px}.workspace{gap:14px;grid-template-columns:1fr 1.08fr}.question-card,.guide-card{padding:20px 18px}.equation{font-size:40px;gap:9px}.operator,.equals{font-size:27px}.equation input{width:66px;height:67px;font-size:36px}.intro{padding:25px 0}.intro h1{font-size:29px}.question-card h2{font-size:15px;margin-top:28px}.keypad{gap:9px}.keypad button{min-height:56px}.guide-card h2{font-size:21px}.step-track{gap:4px}.step-track button{flex-direction:column;min-height:55px;gap:4px}.step-description{font-size:15px;min-height:81px}.step-content{min-height:270px}.step-navigation{margin-top:19px}.visual{padding:10px 6px}.ten-frame{grid-template-columns:repeat(5,17px);grid-template-rows:repeat(2,17px);gap:4px;padding:6px}.ten-frame .bead{width:17px;height:17px}.frames{gap:6px}.math-line{font-size:24px}.remember{margin-top:20px}.check-button{min-height:57px}.gentle-note{line-height:1.9;max-width:240px;align-self:center}.grade-tag{padding:9px 11px}.account{gap:6px}.brand{font-size:21px}.brand small{font-size:10px}.progress-summary{max-width:220px}}
@media(max-width:719px){.app-shell{padding-left:16px;padding-right:16px}.topbar{min-height:76px;gap:8px;flex-wrap:wrap;padding:12px 0}.brand{font-size:20px}.brand-mark{height:40px;width:36px;font-size:30px}.grade-tag{order:3;width:100%;text-align:center;padding:7px}.account{font-size:12px}.avatar{display:none}.intro{padding:23px 0 17px;display:block}.intro h1{font-size:26px}.progress-summary{text-align:left;margin-top:12px;max-width:100%}.progress-summary strong{font-size:17px}.practice-settings{flex-wrap:wrap;padding:11px;gap:10px}.settings-block{flex:1}.settings-block>.segmented{width:100%}.segmented button{flex:1;padding:0 10px}.count-block{flex-basis:40%}.start-button{flex:1;font-size:14px;padding:10px}.workspace{grid-template-columns:1fr;gap:16px}.question-card,.guide-card{padding:20px}.equation{font-size:43px;gap:13px}.keypad{max-width:100%}.keypad button{min-height:52px}.check-button{max-width:100%}.question-card h2{margin-top:18px}.guide-card h2{font-size:23px}.gentle-note{font-size:12px}.step-content{min-height:230px}.footer-extra{display:none}.result-card{padding:24px 17px}.result-numbers{gap:23px}.question-position{font-size:11px}}
@media(prefers-reduced-motion:reduce){*{scroll-behavior:auto!important;transition:none!important}}
.topbar{min-height:48px;gap:10px}.brand{font-size:16px;gap:7px}.brand small,.grade-tag{display:none}.brand-mark{width:27px;height:29px;border-radius:9px 9px 9px 3px;font-size:23px}.brand-mark span{font-size:10px;top:2px;right:2px}.account .avatar{width:26px;height:26px;font-size:20px}.intro{padding:12px 0 11px}.intro h1{font-size:22px;margin-bottom:2px}.intro p:not(.eyebrow){font-size:12px}.practice-settings{margin-bottom:14px;padding:9px 12px;gap:10px}.settings-block{gap:7px}.settings-label{font-size:11px}.segmented button,.segmented.small button{min-height:42px;padding:0 10px;font-size:13px}.start-button{min-height:49px;padding:9px 16px;font-size:14px}.borrow-block{min-width:0}@media(max-width:1150px){.practice-settings{flex-wrap:wrap}.borrow-block{flex:1}.start-button{flex:1}.settings-label{display:none}}@media(max-width:719px){.topbar{min-height:48px;flex-wrap:nowrap;padding:7px 0}.brand{font-size:15px}.account{white-space:nowrap}.intro{padding:12px 0 10px}.intro h1{font-size:22px}.progress-summary{display:none}.practice-settings{gap:8px}.settings-block{flex:1 1 auto}.borrow-block{flex-basis:100%}.borrow-block .segmented{width:100%}.start-button{flex-basis:100%;margin:0}.segmented button,.segmented.small button{font-size:12px;padding:0 6px}}
.guide-actions{display:flex;align-items:center;gap:4px}.guide-actions .text-button{white-space:nowrap}.regroup-scene{position:relative;min-height:108px}.regroup-before{position:absolute;inset:0;opacity:0;pointer-events:none}.regroup-after{position:relative;opacity:1}.regroup-transfer{position:absolute;z-index:2;top:34%;left:24%;padding:6px 11px;border-radius:99px;background:#f4dfb5;color:#875623;box-shadow:0 3px 10px #493d271a;font-size:12px;font-weight:750;white-space:nowrap;opacity:0;pointer-events:none}.visual-motion{overflow:hidden}
@keyframes show-original-tens{0%,30%{opacity:1}63%,100%{opacity:0}}
@keyframes show-exchanged-ones{0%,46%{opacity:0}75%,100%{opacity:1}}
@keyframes move-ten-to-ones{0%,22%{opacity:0;transform:translateX(-28%) scale(.9)}32%{opacity:1;transform:translateX(-25%) scale(1)}67%{opacity:1;transform:translateX(72%) scale(1)}85%,100%{opacity:0;transform:translateX(92%) scale(.9)}}
@keyframes add-one-dot{0%{opacity:0;transform:translateY(12px) scale(.35)}55%{opacity:1;transform:translateY(-2px) scale(1.15)}100%{opacity:1;transform:translateY(0) scale(1)}}
@keyframes cross-out-dot{0%,26%{background:var(--green);border-color:var(--green)}100%{background:#e4d3b1;border-color:#b49c75}}
@keyframes draw-cross{0%,32%{transform:rotate(-45deg) scaleX(0)}100%{transform:rotate(-45deg) scaleX(1)}}
@keyframes settle-dot{0%{opacity:.15;transform:scale(.6)}100%{opacity:1;transform:scale(1)}}
@keyframes bond-left{0%{opacity:0;transform:translateX(20px)}100%{opacity:1;transform:translateX(0)}}
@keyframes bond-right{0%{opacity:0;transform:translateX(-20px)}100%{opacity:1;transform:translateX(0)}}
  .visual-motion.is-animating .regroup-before{animation:show-original-tens 1.3s ease-in-out both}
  .visual-motion.is-animating .regroup-after{animation:show-exchanged-ones 1.3s ease-in-out both}
  .visual-motion.is-animating .regroup-transfer{animation:move-ten-to-ones 1.3s ease-in-out both}
  .visual-motion.is-animating[data-visual-type="addition"] .bead.orange{animation:add-one-dot .65s ease-out both;animation-delay:calc(var(--dot-order)*65ms)}
  .visual-motion.is-animating[data-visual-type="subtraction"] .bead.removed{animation:cross-out-dot .9s ease-in-out both;animation-delay:calc(var(--dot-order)*35ms)}
  .visual-motion.is-animating[data-visual-type="subtraction"] .bead.removed::after{animation:draw-cross .9s ease-in-out both;animation-delay:calc(var(--dot-order)*35ms)}
  .visual-motion.is-animating[data-visual-type="place"] .bead.green,.visual-motion.is-animating[data-visual-type="place"] .ten-rod{animation:settle-dot .55s ease-out both}
  .visual-motion.is-animating[data-visual-type="bond"] .number-chip.orange:nth-of-type(2){animation:bond-left .65s ease-out both}
  .visual-motion.is-animating[data-visual-type="bond"] .number-chip.orange:nth-of-type(3){animation:bond-right .65s ease-out both}
@media(max-width:900px){.guide-actions{gap:0}.guide-actions .text-button{padding:8px 6px;font-size:12px}}
.topbar .grade-tag{display:inline-flex;align-items:center;min-height:34px;padding:5px 12px;font-size:12px;font-weight:700;color:var(--green)}@media(max-width:719px){.topbar .grade-tag{padding:5px 7px;font-size:11px}}