/* Màu và khoảng cách dùng chung. */
:root{--blue:#2259e8;--ink:#182841;--muted:#58677e;--line:#dce4ee;--pale:#edf3ff;--radius:20px}*{box-sizing:border-box}html{scroll-behavior:smooth;scroll-padding-top:28px}body{margin:0;background:#fff;color:var(--ink);font-family:'Be Vietnam Pro',sans-serif;font-size:15px;line-height:1.75}a{color:inherit;text-decoration:none}button,input,select{font:inherit}button,a,input,select{-webkit-tap-highlight-color:transparent}button{cursor:pointer}.wrap{width:min(1160px,calc(100% - 64px));margin:auto}.header{display:flex;align-items:center;justify-content:space-between;gap:24px;height:96px}.brand{display:flex;align-items:center;gap:10px;font-size:23px;font-weight:800;letter-spacing:-1px;white-space:nowrap}.logo{display:grid;place-items:center;width:38px;height:38px;background:var(--blue);color:white;border-radius:12px;font-weight:800;font-size:25px;letter-spacing:-2px}.brand-dot{color:var(--blue);margin-left:-10px}nav{display:flex;gap:32px;font-size:13px;font-weight:500}nav a:hover,.text-link:hover{color:var(--blue)}.button{display:inline-flex;justify-content:center;align-items:center;gap:26px;min-height:52px;padding:13px 22px;background:var(--blue);color:#fff;border:0;border-radius:10px;font-size:14px;font-weight:600;transition:background .2s,transform .2s}.button:hover{background:#1945bc;transform:translateY(-2px)}.button span{font-size:21px}.small{min-height:42px;font-size:12px;padding:9px 16px;gap:20px}.hero{display:grid;grid-template-columns:1.05fr 1fr;gap:65px;align-items:center;padding-top:56px;padding-bottom:84px}.eyebrow{font-size:11px;font-weight:600;letter-spacing:1.2px;color:var(--muted);margin:0 0 24px}.hero .eyebrow{letter-spacing:0;display:flex;align-items:center;gap:8px}.status-dot{width:7px;height:7px;border-radius:50%;background:var(--blue)}h1{font-size:clamp(42px,4.5vw,62px);line-height:1.18;letter-spacing:-2.9px;font-weight:800;margin:0 0 24px}h1 span{color:var(--blue)}.lead{max-width:460px;color:var(--muted);font-size:16px;margin:0 0 30px;line-height:1.9}.text-link{display:block;width:fit-content;font-size:12px;margin-top:18px;color:var(--muted)}.text-link span{margin-left:15px}.study-scene{position:relative;padding:28px 16px 24px;background-color:var(--pale);background-image:linear-gradient(#dbe6fa88 1px,transparent 1px),linear-gradient(90deg,#dbe6fa88 1px,transparent 1px);background-size:28px 28px;border-radius:30px}.scene-note{font-size:12px;color:#426297;text-align:center;margin-bottom:17px}.chat{background:white;border:1px solid #dce6f6;border-radius:17px;box-shadow:0 16px 36px #153b7b13;overflow:hidden}.chat-top{display:flex;align-items:center;gap:10px;padding:18px;border-bottom:1px solid var(--line)}.small-logo{width:32px;height:32px;font-size:22px;border-radius:9px}.chat-top strong{display:block;font-size:12px}.chat-top small{display:block;color:var(--muted);font-size:10px}.chat-symbol{margin-left:auto;color:var(--blue);font-size:24px}.chat-body{padding:18px;font-size:11px}.topic{font-size:9px;letter-spacing:1.4px;color:var(--muted);margin:0 0 12px}.bubble{background:#edf3ff;border-radius:12px 12px 3px 12px;padding:12px 15px;margin:0 0 18px auto;width:88%;color:#254776}.bubble strong{font-size:14px}.ai-message{display:flex;gap:9px;margin-bottom:16px}.avatar{flex-shrink:0;display:grid;place-items:center;width:25px;height:25px;background:var(--pale);color:var(--blue);border-radius:8px;font-weight:800}.ai-message p{margin:5px 0 0;color:var(--muted)}.math{margin-top:10px;padding:7px 12px;border-left:2px solid var(--blue);background:#f6f8fd;font-size:15px;font-weight:500}.compact{width:fit-content;margin-bottom:15px}.practice{display:flex;justify-content:space-between;width:100%;border:1px solid #cddcf9;background:white;color:var(--blue);padding:9px 12px;border-radius:8px;font-size:11px}.practice:hover{background:var(--pale)}.practice-result{padding:12px;background:var(--pale);border-radius:8px}.chat-bottom{background:#f8faff;color:var(--muted);font-size:10px;text-align:center;padding:10px}.scene-tag{position:absolute;bottom:8px;right:-16px;background:#fff8dc;border:1px solid #f1e8ba;border-radius:9px;box-shadow:0 5px 15px #2836410b;padding:9px 16px;font-size:11px;transform:rotate(-3deg)}.scene-tag span{margin-right:8px}.promise-strip{border-block:1px solid var(--line);background:#fafcff}.promises{display:flex;justify-content:space-between;gap:20px;padding-block:22px;font-size:12px;color:var(--muted)}.promises span::before{content:'✳';color:var(--blue);margin-right:12px}h2{font-size:clamp(27px,3vw,37px);letter-spacing:-1.3px;line-height:1.4;margin:0 0 16px;font-weight:700}h3{font-size:17px;line-height:1.5;margin:14px 0 10px}.problem{display:grid;grid-template-columns:1fr 1fr;gap:90px;padding-block:86px}.problem .eyebrow{margin-bottom:18px}.problem-copy{padding-top:24px;color:var(--muted);font-size:14px}.problem-copy p{margin:0 0 16px}.features-section{padding:72px 0 80px;background:#f8faff}.section-description{color:var(--muted);font-size:14px;margin:0 0 34px}.features{display:grid;grid-template-columns:1.12fr 1fr 1fr;gap:16px}.feature{border:1px solid var(--line);background:#fff;border-radius:var(--radius);padding:27px}.feature p{font-size:13px;color:var(--muted);margin:0}.feature-blue{grid-row:span 2;background:var(--blue);border-color:var(--blue);color:#fff}.feature-blue p{color:#e4ecff}.feature-icon{display:grid;place-items:center;background:var(--pale);color:var(--blue);width:39px;height:39px;border-radius:11px;font-size:24px;font-weight:500}.feature-blue .feature-icon{background:#ffffff26;color:white}.mini-steps{display:grid;gap:16px;margin-top:33px;font-size:12px}.mini-steps span{border-top:1px solid #ffffff33;padding-top:13px}.feature-teacher{grid-column:span 2;display:grid;grid-template-columns:40px 1fr;column-gap:18px;background:#edf2ec}.feature-teacher .feature-icon{grid-row:span 3;background:#dde8d9;color:#50684b}.feature-teacher h3{margin-top:0}.teacher-note{font-size:11px;color:#51694d;margin-top:16px}.how{padding-block:86px}.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:46px;margin-top:45px}.step-number{font-size:13px;color:var(--blue);border:1px solid #d2defa;width:42px;height:42px;border-radius:50%;display:grid;place-items:center}.steps h3{margin-top:20px}.steps p{font-size:13px;color:var(--muted);margin:0}.signup-section{background:#edf3ff;padding:74px 0}.signup{display:grid;grid-template-columns:1.1fr 1fr;gap:100px;align-items:center}.signup h2{font-size:39px}.signup>div>p:not(.eyebrow){font-size:14px;color:var(--muted);max-width:430px}.signup-doodle{display:block;margin-top:36px;font-size:14px;transform:rotate(-3deg);color:var(--blue)}form{padding:30px;background:#fff;border-radius:20px;border:1px solid #dfe8f8}form h3{margin:0 0 22px}label{display:block;font-size:12px;font-weight:500;margin-bottom:7px}input,select{width:100%;min-height:45px;border:1px solid #d9e1eb;border-radius:8px;background:#fcfdff;padding:10px 12px;color:var(--ink);font-size:13px;margin-bottom:16px}form .button{width:100%;margin-top:4px}.form-note{font-size:10px;color:var(--muted);margin:13px 0 0}#form-status{font-size:12px;color:#2853ae;margin:10px 0 0}.footer{display:flex;justify-content:space-between;gap:30px;padding-block:38px}.footer .brand{font-size:20px}.footer p{font-size:10px;color:var(--muted);margin:12px 0 0}.footer>div:last-child{text-align:right;padding-top:8px}.footer>div:last-child a{font-size:12px}:focus-visible{outline:3px solid #d48b00;outline-offset:4px}.skip{position:absolute;top:-80px;left:20px;background:white;padding:12px;z-index:10}.skip:focus{top:10px}[hidden]{display:none}
@media(max-width:1024px){.hero{gap:30px}h1{font-size:48px}.signup{gap:45px}.scene-tag{right:0}.features{grid-template-columns:1fr 1fr}.feature-blue{grid-row:auto}.feature-teacher{grid-column:auto;display:block}.feature-teacher h3{margin-top:14px}.teacher-note{display:block}.problem{gap:40px}.signup h2{font-size:32px}}
@media(max-width:767px){.wrap{width:calc(100% - 36px)}.header{height:auto;min-height:78px;flex-wrap:wrap;gap:10px;padding-block:16px}.brand{font-size:20px}.header .small{font-size:10px;padding:8px 12px;gap:10px}nav{order:3;width:100%;justify-content:center;gap:26px;font-size:12px;padding-top:10px}.hero{grid-template-columns:1fr;padding-top:36px;padding-bottom:45px;gap:38px}h1{font-size:clamp(36px,8.9vw,57px);letter-spacing:-2px}.hero .eyebrow{font-size:10px;margin-bottom:20px}.lead{font-size:14px}.study-scene{max-width:490px;width:100%;margin:auto;padding:20px 12px 24px}.promises{display:grid;grid-template-columns:1fr 1fr;gap:14px;font-size:10px;padding-block:20px}.promises span::before{margin-right:6px}.problem{grid-template-columns:1fr;padding-block:52px;gap:5px}.problem-copy{padding-top:0}.features-section{padding-block:48px}.features{gap:12px}.feature{padding:20px}.feature h3{font-size:15px}.feature p{font-size:12px}.feature-blue{grid-column:span 2}.mini-steps{grid-template-columns:repeat(3,1fr);gap:10px;margin-top:22px;font-size:10px}.feature-teacher{grid-column:span 2}.how{padding-block:52px}.steps{grid-template-columns:1fr;gap:27px;margin-top:28px}.steps article{position:relative;padding-left:61px}.step-number{position:absolute;left:0;top:0}.steps h3{margin-top:0}.signup-section{padding-block:48px}.signup{grid-template-columns:1fr;gap:30px}.signup h2{font-size:30px}.signup-doodle{margin-top:24px}form{padding:23px}.footer{flex-direction:column;gap:20px;padding-block:30px}.footer>div:last-child{text-align:left}.eyebrow{font-size:10px}}
@media(max-width:360px){.features{grid-template-columns:1fr}.feature-blue,.feature-teacher{grid-column:auto}.promises{font-size:9px}.chat-body{padding:12px}.chat-top{padding:12px}.hero .button{font-size:12px}}
@media(prefers-reduced-motion:reduce){html{scroll-behavior:auto}*,*::before,*::after{transition:none!important}}