:root{--navy:#001a42;--ink:#061463;--yellow:#ffe100;--red:#ff0735;--orange:#ff8700;--green:#00bf62;--blue:#008eff;--purple:#a000ff;--line:#dceeff}*{box-sizing:border-box}body{margin:0;background:linear-gradient(120deg,#fff,#f2faff);color:var(--ink);font:16px/1.45 'Arial',sans-serif}a{color:inherit;text-decoration:none}button,input{font:inherit}button,a,input{touch-action:manipulation}button{cursor:pointer}a:focus-visible,button:focus-visible,input:focus-visible{outline:3px solid #ffbf00;outline-offset:3px}.skip{position:absolute;top:-100px;background:white;padding:10px;z-index:10}.skip:focus{top:4px}header{background:var(--navy);color:white;border-bottom:4px solid #ffd600;position:relative;z-index:2}.header-inner{max-width:1320px;margin:auto;display:flex;align-items:center;gap:22px;padding:15px 20px}.brand{font-weight:900;font-size:25px;white-space:nowrap;letter-spacing:-1px}.yellow{color:var(--yellow)}nav{display:flex;gap:15px;align-items:center;flex:1}nav a{font-weight:700;font-size:14px;white-space:nowrap;padding:8px 0}nav a[aria-current=page]{color:var(--yellow);box-shadow:0 3px var(--yellow)}.youtube{display:inline-flex;align-items:center;justify-content:center;gap:8px;background:var(--red);color:white;padding:11px 16px;border-radius:7px;font-weight:800;white-space:nowrap;font-size:14px;box-shadow:0 3px 8px #ff07352a}.menu-toggle{display:none;background:transparent;color:white;border:1px solid #ffffff60;border-radius:5px;padding:5px 12px;font-size:24px}main{max-width:1220px;margin:0 auto;padding:20px 24px 50px;min-height:75vh}.breadcrumb{font-size:14px;margin-bottom:16px}.breadcrumb a{font-weight:700}.sprite{display:block;position:relative;overflow:hidden;border-radius:10px;background:#eaf5ff;isolation:isolate}.sprite img{position:absolute;max-width:none;height:auto;pointer-events:none}.home-hero{margin-bottom:20px}.grade-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:17px;margin:20px 0}.grade-link{display:flex;align-items:center;gap:14px;color:white;padding:17px 20px;border-radius:9px;box-shadow:0 4px 8px #001a4220;transition:transform .15s}.grade-link:hover{transform:translateY(-3px)}.grade-link .icon{font-size:38px}.grade-link strong{display:block;font-size:23px;font-weight:900}.grade-link small{font-size:14px}.orange{--tone:var(--orange);--pale:#fff1e7}.green{--tone:var(--green);--pale:#eafff0}.blue{--tone:var(--blue);--pale:#e8f5ff}.purple{--tone:var(--purple);--pale:#f3e8ff}.grade-link,.grade-banner,.chip.active{background:var(--tone)}.section-heading{display:flex;align-items:center;justify-content:space-between;gap:10px;margin:24px 0 14px}.section-heading h2{font-size:25px;margin:0}.section-heading a{font-size:14px;color:#1539ed;font-weight:bold}.featured{display:grid;grid-template-columns:repeat(4,1fr);gap:18px}.card .sprite{aspect-ratio:16/10}.card h3{font-size:17px;margin:8px 0 5px;line-height:1.25}.badge{display:inline-block;background:var(--tone,var(--purple));color:white;font-size:13px;font-weight:700;border-radius:5px;padding:3px 12px}.card-status{display:block;font-size:13px;margin-top:5px;color:#52647d}.benefits{display:grid;grid-template-columns:repeat(4,1fr);gap:10px;margin-top:30px}.benefit{background:#fff;border:1px solid var(--line);box-shadow:0 3px 8px #0075d415;border-radius:9px;padding:16px;display:flex;gap:12px;align-items:center}.benefit span{font-size:30px}.benefit strong{display:block;font-size:15px}.benefit small{font-size:13px}.note{background:#fff277;padding:15px 25px;font-weight:900;text-align:center;max-width:360px;margin:25px auto 0;transform:rotate(-2deg);border-radius:3px;font-size:20px}.grade-banner{color:white;padding:30px;border-radius:12px;display:flex;align-items:center;gap:24px;min-height:220px}.grade-banner .icon{font-size:75px}.grade-banner h1{font-size:40px;margin:0}.grade-banner p{font-size:20px;margin:5px 0}.banner-art{margin-bottom:18px}.tabs{display:flex;gap:10px;flex-wrap:wrap;margin:18px 0}.tab,.chip{border:0;background:#eef6ff;color:var(--ink);border-radius:7px;padding:11px 20px;font-weight:700;font-size:15px}.tab[aria-pressed=true]{background:var(--red);color:white}.chip.active{color:white}.video-list{display:grid;gap:12px}.video-row{display:flex;align-items:center;gap:22px;background:white;padding:10px 15px;border-radius:12px;border:1px solid #e8f3fc;box-shadow:0 3px 12px #0060a006;min-height:112px}.video-row .thumb{width:285px;flex-shrink:0;aspect-ratio:3.56}.video-row h3{margin:0;font-size:19px}.video-row p{margin:4px 0;font-size:16px}.video-row .arrow{margin-left:auto;flex-shrink:0;background:#7bbaff;color:white;width:32px;height:32px;display:grid;place-items:center;border-radius:50%}.video-row .pending{font-size:13px;color:#52647d}.play{position:absolute;bottom:10%;left:5%;background:#000b;border:2px solid white;border-radius:50%;width:32px;height:32px;display:grid;place-items:center;color:white}.real-thumb{width:100%;height:100%;object-fit:cover;display:block}.thumb{overflow:hidden;border-radius:8px;background:#eaf5ff;position:relative}.page-title{display:flex;align-items:center;gap:20px;margin:15px 0 20px}.page-title .icon{font-size:46px}.page-title h1{margin:0;font-size:36px}.page-title p{margin:2px 0}.search{width:100%;padding:12px 15px;border:1px solid #b4d7ff;border-radius:8px;margin:0 0 20px;background:white;color:var(--ink)}.topic-groups{display:grid;gap:15px}details{background:var(--pale);border-radius:12px;padding:0 18px;border:1px solid var(--line)}summary{cursor:pointer;padding:18px 0;font-size:23px;font-weight:900;color:var(--tone)}.topic-list{list-style:none;margin:0 0 18px;padding:0}.topic-list li+li{margin-top:6px}.topic-list a{display:flex;align-items:center;gap:14px;background:#ffffffb0;padding:12px 15px;border-radius:7px}.topic-list a:hover{background:white}.topic-list .number{background:var(--tone);color:white;border-radius:50%;width:27px;height:27px;display:grid;place-items:center}.topic-list .arrow{margin-left:auto;color:var(--tone)}.about{max-width:900px;margin:auto}.about p{font-size:18px;line-height:1.7}.about .benefits{grid-template-columns:repeat(2,1fr)}.empty{background:white;border:1px solid var(--line);border-radius:10px;padding:30px;text-align:center}footer{max-width:1220px;margin:auto;border-top:1px solid var(--line);padding:22px 24px;display:flex;gap:12px;font-size:14px}footer strong{color:var(--navy)}footer a{margin-left:auto}@media(min-width:1000px){.all-videos .video-row .thumb{width:220px}}@media(max-width:1200px){.header-inner{gap:14px;flex-wrap:wrap}nav{order:3;flex-basis:100%;justify-content:center}.header-inner>.youtube{margin-left:auto}.grade-link{padding:15px 12px;gap:7px}.grade-link strong{font-size:20px}}@media(max-width:720px){main{padding:15px 14px 35px}.header-inner{padding:12px 14px;gap:12px}.brand{font-size:22px}.menu-toggle{display:block;margin-left:auto}.header-inner>.youtube{font-size:13px;padding:9px 12px;margin-left:0}nav{display:none;flex-direction:column;align-items:stretch;gap:0}nav.open{display:flex}nav a{padding:12px;border-bottom:1px solid #ffffff20}.grade-grid{grid-template-columns:repeat(2,1fr);gap:10px}.grade-link strong{font-size:21px}.grade-link .icon{font-size:30px}.featured{grid-template-columns:repeat(2,1fr);gap:14px}.section-heading h2{font-size:21px}.section-heading a{font-size:12px}.benefits{grid-template-columns:repeat(2,1fr)}.benefit{padding:12px;gap:8px}.benefit strong{font-size:14px}.video-row{padding:8px;gap:10px;min-height:90px}.video-row .thumb{width:36%;aspect-ratio:1.6}.video-row h3{font-size:16px}.video-row p{font-size:14px}.video-row .arrow{width:25px;height:25px}.video-row .pending{font-size:12px}.tabs{gap:6px}.tab,.chip{padding:9px 12px;font-size:14px}.page-title h1{font-size:29px}.page-title{gap:10px}.grade-banner{min-height:155px;padding:20px;gap:12px}.grade-banner h1{font-size:27px}.grade-banner .icon{font-size:44px}.grade-banner p{font-size:16px}summary{font-size:20px}.about .benefits{grid-template-columns:1fr}.about p{font-size:16px}}@media(prefers-reduced-motion:reduce){*{transition:none!important}}

.thumb{display:block}.card .thumb{width:100%;aspect-ratio:16/10}.thumb .real-thumb{position:absolute;inset:0;width:100%;height:100%;object-fit:cover}


.hd-banner{display:block;overflow:hidden;border-radius:10px}.hd-banner img{display:block;width:100%;height:auto}.hd-banner.banner-art{aspect-ratio:4.3}.hd-banner.banner-art img{height:100%;object-fit:fill}.hd-video{background:linear-gradient(120deg,var(--tone),#003d83);aspect-ratio:3.56;display:flex;align-items:stretch}.hd-person{position:relative;width:37%;overflow:hidden;flex-shrink:0}.hd-person img{position:absolute;height:100%;width:auto;max-width:none;right:0}.green-person{filter:hue-rotate(15deg)}.hd-video-copy{display:flex;flex-direction:column;justify-content:center;align-items:flex-start;gap:5px;padding:8px;color:white;min-width:0;flex:1}.hd-video-copy strong{font-size:clamp(14px,1.5vw,23px);line-height:1.05}.hd-video-copy>span{background:#ffec00;color:#002352;font-weight:800;padding:2px 6px;border-radius:3px;font-size:13px}.card .hd-video{aspect-ratio:16/10}.card .hd-person{width:40%}.card .hd-video-copy{padding:6px}.card .hd-video-copy strong{font-size:20px}.card .hd-video-copy>span{font-size:12px}@media(max-width:720px){.video-row .hd-video-copy{padding:4px;gap:3px}.video-row .hd-video-copy strong{font-size:12px}.video-row .hd-video-copy>span{font-size:9px;padding:1px 3px}.card .hd-video-copy strong{font-size:16px}.card .hd-video-copy>span{font-size:10px}}


.hd-class-banner{position:relative;display:flex;align-items:center;gap:20px;aspect-ratio:4.3;border-radius:12px;overflow:hidden;background:linear-gradient(110deg,var(--tone),#00d0d4);color:white;margin-bottom:18px;padding:25px}.hd-class-banner.orange{background:linear-gradient(110deg,#ff433d,#ffa400,#23d953)}.hd-class-banner.purple{background:linear-gradient(110deg,#b000ff,#6200ec,#b24bff)}.hd-class-icon{font-size:64px;position:relative;z-index:1}.hd-class-text{position:relative;z-index:1;max-width:65%}.hd-class-text strong{display:block;font-size:clamp(24px,3.2vw,44px);font-weight:900;line-height:1.15}.hd-class-text>span{display:block;font-weight:700;font-size:20px;line-height:1.3;margin-top:10px}.hd-class-person{position:absolute;right:0;top:0;width:31%;height:100%;overflow:hidden}.hd-class-person img{position:absolute;right:0;top:0;height:100%;width:auto;max-width:none}.hd-person img{height:140%;top:-10%;right:-8px}@media(max-width:720px){.hd-class-banner{padding:10px;gap:8px;aspect-ratio:3.6}.hd-class-icon{font-size:28px}.hd-class-text{max-width:64%}.hd-class-text strong{font-size:clamp(17px,4.5vw,27px)}.hd-class-text>span{font-size:clamp(10px,2.5vw,15px);margin-top:5px}}

.worksheet-section{margin:28px 0 20px}.worksheet-card{background:#f0f7ff;border:1px solid #c8dfff;border-radius:14px;padding:22px}.worksheet-card h3{font-size:24px;margin:12px 0}.worksheet-card p{line-height:1.6}.worksheet-button{display:inline-block;background:#075bdb;color:white!important;padding:12px 18px;border-radius:8px;font-weight:bold}.worksheet-download{display:inline-block;padding:12px 18px;font-weight:bold}