/*
  Giao diện desktop chính thức — áp dụng từ 960px trở lên.
  Mobile/tablet nhỏ tiếp tục dùng css/landing.css.
*/
@media (min-width:960px){
  :root{
    --desktop-max:1180px;
    --desktop-gutter:40px;
  }

  html{scroll-padding-top:146px}
  body{
    padding:0;
    min-width:960px;
    background:
      radial-gradient(900px 620px at 11% 8%,rgba(105,67,189,.34),transparent 65%),
      radial-gradient(820px 600px at 91% 22%,rgba(27,74,150,.38),transparent 66%),
      linear-gradient(180deg,#28185d 0%,#1b123f 55%,#171034 100%);
  }
  .container{width:min(calc(100% - 80px),var(--desktop-max))}
  main,.footer{
    width:100%;max-width:none;margin:0;
    border:0;border-radius:0;background:transparent;
  }
  main{overflow:hidden}

  /* Header */
  .topbar{
    width:100%;max-width:none;height:76px;margin:0;border-radius:0;
    background:rgba(20,13,55,.88);
    box-shadow:0 10px 34px rgba(5,3,24,.16);
  }
  .topbar-inner{gap:24px}
  .brand-logo{width:172px}
  .header-cta{
    min-width:132px;padding:12px 20px;
    font-size:12px;letter-spacing:.2px;text-align:center;
    transition:transform .16s ease,background .16s ease;
  }
  .header-cta:hover{transform:translateY(-1px);background:rgba(255,211,77,.19)}

  /* Hero hai cột */
  .hero{
    position:relative;padding:76px 0 88px;text-align:left;
    background:
      radial-gradient(620px 420px at 78% 36%,rgba(84,49,177,.24),transparent 70%),
      linear-gradient(180deg,rgba(255,255,255,.018),transparent);
  }
  .hero:before{
    content:"";position:absolute;inset:0;pointer-events:none;opacity:.17;
    background-image:
      linear-gradient(rgba(255,255,255,.035) 1px,transparent 1px),
      linear-gradient(90deg,rgba(255,255,255,.035) 1px,transparent 1px);
    background-size:64px 64px;
    -webkit-mask-image:linear-gradient(90deg,#000,transparent 74%);
    mask-image:linear-gradient(90deg,#000,transparent 74%);
  }
  .hero .container{
    position:relative;z-index:1;
    display:grid;
    grid-template-columns:minmax(360px,.9fr) minmax(430px,1.1fr);
    grid-template-areas:
      "copy art"
      "actions art"
      "account art"
      "trust art";
    column-gap:44px;row-gap:0;align-items:center;
  }
  .hero-art{
    grid-area:art;margin:0;align-self:center;
    border-radius:34px;overflow:hidden;
    border:1px solid rgba(255,255,255,.15);
    background:#10072f;
    box-shadow:0 38px 90px rgba(4,2,22,.46),0 0 0 8px rgba(255,255,255,.025);
  }
  .hero-art:after{
    height:20%;
    background:linear-gradient(180deg,transparent,rgba(16,7,47,.66));
  }
  .hero-art img{width:100%;height:auto;transition:transform .35s ease}
  .hero-art:hover img{transform:scale(1.015)}
  .hero-copy{grid-area:copy;margin:0;padding:0;align-self:end;max-width:560px}
  .eyebrow{font-size:12px;letter-spacing:1.35px}
  .hero h1{
    margin:13px 0 17px;font-size:clamp(44px,4.2vw,58px);line-height:1.01;letter-spacing:-2.1px;
  }
  .hero-desc{max-width:570px;font-size:17px;line-height:1.65;color:#e9e7f8}
  .hero-actions{grid-area:actions;max-width:530px;gap:14px;margin-top:26px}
  .role-cta{min-height:72px;border-radius:20px}
  .role-cta strong{font-size:15px}.role-cta small{font-size:10.5px}
  .role-cta:hover{transform:translateY(-2px);filter:brightness(1.06)}
  .no-account{
    grid-area:account;margin-top:17px;justify-content:flex-start;
    font-size:12px;
  }
  .trust-strip{grid-area:trust;justify-content:flex-start;gap:9px;margin-top:16px}
  .trust-strip span{padding:9px 12px;font-size:11px}

  /* Khối chọn vai trò */
  .role-zone{
    width:min(calc(100% - 80px),var(--desktop-max));
    margin:-29px auto 12px;
    display:grid;grid-template-columns:minmax(0,1fr) 470px;align-items:center;
    border:1px solid rgba(255,255,255,.105);
    border-radius:24px;
    background:linear-gradient(135deg,rgba(51,34,116,.96),rgba(31,22,75,.96));
    box-shadow:0 24px 60px rgba(5,3,24,.30);
    overflow:hidden;
    position:relative;z-index:4;
  }
  .role-guide{padding:0;background:none}
  .role-guide .container,.role-dock-wrap .container{width:100%;max-width:none;margin:0}
  .role-guide .container{padding:28px 34px}
  .role-guide p{font-size:14px;line-height:1.6}
  .role-guide strong{font-size:16px}
  .role-dock-wrap{
    padding:0;background:none;border:0;
    border-left:1px solid rgba(255,255,255,.08);
  }
  .role-dock-wrap .container{padding:24px 30px}
  .role-switch{padding:5px;border-radius:16px}
  .role-tab{min-height:44px;font-size:12px;border-radius:12px}

  /* Thanh đổi vai trò khi cuộn */
  .quick-role-bar{
    left:0;right:0;top:76px;width:auto;
    transform:translateY(calc(-100% - 3px));
    border-inline:0;
  }
  .quick-role-bar.is-visible{transform:translateY(0)}
  .quick-role-bar .container{display:flex;justify-content:center}
  .quick-role-switch{width:430px;min-height:48px}
  .quick-role-switch .role-tab{min-height:38px}
  .section[id],.role-guide[id]{scroll-margin-top:146px}

  /* Nhịp section chung */
  .section{padding:86px 0 12px}
  .section-head{max-width:760px;margin-bottom:30px}
  .section-head h2{margin:8px 0 12px;font-size:38px;line-height:1.1;letter-spacing:-1.15px}
  .section-desc{font-size:15px;line-height:1.65;margin-bottom:0}

  /* Lợi ích */
  .benefits-section{padding-top:96px}
  .benefit-grid{grid-template-columns:repeat(3,minmax(0,1fr));gap:20px}
  .benefit-card{
    display:block;min-height:220px;padding:26px;border-radius:24px;
    transition:transform .18s ease,border-color .18s ease,background .18s ease;
  }
  .benefit-card:hover{
    transform:translateY(-4px);border-color:rgba(255,211,77,.25);
    background:linear-gradient(145deg,rgba(255,255,255,.115),rgba(255,255,255,.045));
  }
  .benefit-icon{width:58px;height:58px;margin-bottom:22px;border-radius:19px;font-size:28px}
  .benefit-card h3{font-size:20px;margin:0 0 10px}
  .benefit-card p{font-size:14px;line-height:1.62}

  /* Ba nhóm tính năng — luôn mở, không còn hành vi accordion trên PC */
  .features-section{padding-top:102px;padding-bottom:18px}
  .feature-accordion-list{
    grid-template-columns:repeat(3,minmax(0,1fr));
    gap:20px;
    align-items:stretch;
    margin-top:28px;
  }
  .feature-accordion{
    display:flex;
    flex-direction:column;
    align-self:stretch;
    min-width:0;
  }
  .feature-accordion .mode-tab{
    flex:0 0 136px;
    min-height:136px;
    height:136px;
    padding:25px 23px;
    grid-template-columns:54px minmax(0,1fr);
    gap:14px;
    border-radius:27px 27px 16px 16px;
    cursor:default;
    pointer-events:none;
    transform:none;
    filter:saturate(1.06) brightness(1.04);
    border-color:rgba(255,211,77,.30);
  }
  .feature-accordion .mode-arrow{display:none}
  .mode-icon{font-size:39px}
  .mode-copy strong{font-size:22px}
  .mode-copy small{margin-top:8px;font-size:13px;line-height:1.45}
  .feature-accordion .feature-detail,
  .feature-accordion .feature-detail[hidden]{
    display:flex!important;
    flex:1 1 auto;
    flex-direction:column;
    height:auto;
    margin:-8px 0 0;
    padding:31px 24px 24px;
    border-radius:0 0 25px 25px;
  }
  .feature-detail-head{grid-template-columns:58px minmax(0,1fr);gap:14px}
  .feature-detail-icon{width:58px;height:58px;border-radius:19px;font-size:30px}
  .feature-role{font-size:10.5px!important}
  .feature-detail h3{font-size:20px;line-height:1.28}
  .feature-detail-head p{font-size:12.5px;line-height:1.5}
  .feature-list{flex:0 0 auto;gap:12px;margin-top:20px}
  .feature-list li{padding-left:31px;font-size:13.5px;line-height:1.58}
  .feature-list li:before{width:21px;height:21px}
  .feature-benefit{
    margin-top:auto;
    padding:13px 14px;
    font-size:12.5px;
    line-height:1.58;
  }
  .context-cta{min-height:50px;margin-top:14px;font-size:12.5px;border-radius:15px}

  /* Trải nghiệm: mô tả bên trái, demo bên phải */
  .experience-section{padding:108px 0 22px}
  .experience-section .container{
    display:grid;grid-template-columns:360px minmax(0,1fr);gap:68px;align-items:start;
  }
  .experience-section .section-head{
    max-width:none;margin:0;position:sticky;top:154px;
  }
  #studentExperience,#teacherExperience{min-width:0}
  .demo-app{max-width:470px;margin:0 auto;border-radius:29px}
  .teacher-demo{max-width:none;margin:0;min-height:560px;padding:25px 26px 28px;border-radius:29px}
  .demo-screen{padding:22px 21px 24px}
  .demo-title{font-size:24px}.demo-sub{font-size:13px}
  .teacher-progress{max-width:560px;margin:0 auto 25px}
  .teacher-screen{max-width:720px;margin:0 auto;padding-top:27px}
  .teacher-screen-title strong{font-size:21px}
  .teacher-screen-title small{font-size:12.5px}
  .mock-form{grid-template-columns:repeat(3,minmax(0,1fr));gap:14px;margin-bottom:20px}
  .mock-form label{font-size:11px;gap:7px}
  .mock-form select{height:48px;padding-inline:12px;font-size:12.5px}
  .review-toolbar{margin-bottom:14px}
  .review-toolbar button{padding:10px 12px;font-size:10px}
  .review-toolbar span{font-size:11px}
  .mock-questions{gap:12px;margin-bottom:16px}
  .mock-question{padding:15px;border-radius:17px}
  .mock-question-title{font-size:10.5px}.mock-expression{font-size:21px}.mock-answer{font-size:12px}
  .mock-actions button{padding:8px 10px;font-size:9px}
  .experience-note{max-width:720px;margin-top:15px;text-align:center;font-size:12px}

  /* Cách sử dụng */
  .how-section{padding-top:106px}
  .steps{grid-template-columns:repeat(2,minmax(0,1fr));gap:18px}
  .step{
    position:relative;display:block;min-height:190px;padding:24px 22px;border-radius:22px;
  }
  .step:not(:last-child):after{
    display:none;
    content:"→";position:absolute;right:-15px;top:50%;z-index:2;
    transform:translateY(-50%);color:var(--gold);font-size:22px;font-weight:900;
  }
  .step-num{width:46px;height:46px;margin-bottom:20px;border-radius:15px;font-size:15px}
  .step h3{font-size:16px;line-height:1.35}
  .step p{margin-top:8px;font-size:13px;line-height:1.55}

  /* Gallery 4 cột */
  .gallery-section{padding-top:108px}
  .gallery{
    display:grid;grid-template-columns:repeat(2,minmax(0,1fr));gap:18px;
    overflow:visible;padding:0;margin:0;scroll-snap-type:none;
  }
  .gallery-card{flex:none;width:auto;border-radius:22px;transition:transform .18s ease,border-color .18s ease}
  .gallery-card:hover{transform:translateY(-4px);border-color:rgba(96,189,255,.25)}
  .gallery-media{aspect-ratio:3/4}
  .gallery-meta{padding:15px 16px 17px}
  .gallery-meta h3{font-size:15px}.gallery-meta p{font-size:12px;line-height:1.5}

  /* FAQ */
  .faq-section{padding-top:104px}
  .faq-list{grid-template-columns:repeat(2,minmax(0,1fr));gap:14px;align-items:start}
  .faq-list details{border-radius:19px}
  .faq-list summary{padding:18px 50px 18px 18px;font-size:14px}
  .faq-list details p{padding:0 18px 18px;font-size:12.5px;line-height:1.62}

  /* CTA cuối */
  .final-cta{padding:102px 0 82px}
  .final-box{
    display:grid;grid-template-columns:minmax(0,1fr) minmax(380px,440px);column-gap:40px;align-items:center;
    padding:44px 48px;border-radius:30px;text-align:left;
  }
  .final-box>.eyebrow{grid-column:1}
  .final-box>h2{grid-column:1;margin:8px 0 10px;font-size:38px;line-height:1.12}
  .final-box>p{grid-column:1;font-size:14px;line-height:1.6}
  .final-box>.hero-actions{grid-column:2;grid-row:1/4;margin:0;max-width:none;width:100%}

  /* Footer */
  .footer{padding:38px 0 42px;border-radius:0}
  .footer-inner{
    display:grid;grid-template-columns:180px minmax(300px,1fr) auto;gap:28px 42px;
    align-items:center;text-align:left;
  }
  .footer-brand{justify-content:flex-start}
  .footer-brand img{width:164px}
  .footer-desc{max-width:520px;margin:0;font-size:12px;line-height:1.6}
  .footer-links{justify-content:flex-end;gap:20px;font-size:12px}
  .copyright{grid-column:2/4;margin:0;text-align:right;font-size:10px}

  /* CTA role-aware gọn ở góc phải */
  .sticky-cta{display:none}

  /* Viewer */
  .image-viewer{padding:34px}
  .image-viewer-inner{width:min(100%,760px);height:min(92dvh,1080px)}
  .image-viewer-close{top:12px;right:12px}
  .image-viewer-caption{left:18px;right:70px;bottom:18px;font-size:13px}
}

@media (min-width:1180px){
  .section-head h2{font-size:42px;letter-spacing:-1.3px}
  .steps{grid-template-columns:repeat(4,minmax(0,1fr))}
  .step:not(:last-child):after{display:block}
  .gallery{grid-template-columns:repeat(4,minmax(0,1fr))}
  .final-box{grid-template-columns:minmax(0,1fr) 500px;column-gap:50px}
}

@media (min-width:1280px){
  .container{width:min(calc(100% - 96px),1240px)}
  .role-zone{width:min(calc(100% - 96px),1240px)}
  .hero .container{grid-template-columns:minmax(0,.84fr) minmax(610px,1.16fr);column-gap:78px}
  .hero h1{font-size:62px}
}