:root{
  --teal:#1793a8;
  --teal-dark:#0f7688;
  --navy:#1a4b8c;
  --navy-light:#2f6fb0;
  --bg:#f7fafb;
  --text:#333333;
  --muted:#6b7280;
}
*{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}
body{
  font-family:'Kanit',sans-serif;
  color:var(--text);
  background-color:var(--bg);
  background-image:linear-gradient(rgba(247,250,251,.88),rgba(247,250,251,.88)),url('../images/hero.webp');
  background-repeat:no-repeat;
  background-position:center;
  background-size:cover,138vmin auto;
  background-attachment:fixed;
  line-height:1.7;
}
a{text-decoration:none;color:inherit;}
img{max-width:100%;height:auto;display:block;}
.container{max-width:1100px;margin:0 auto;padding:0 24px;}

/* Header */
header{
  background:var(--teal);
  position:sticky;
  top:0;
  z-index:100;
  box-shadow:0 2px 10px rgba(0,0,0,.08);
}
.nav-wrap{
  display:flex;
  align-items:center;
  justify-content:space-between;
  padding:14px 24px;
  max-width:1100px;
  margin:0 auto;
}
.logo-link{display:flex;align-items:center;gap:12px;}
.logo-img{height:48px;width:auto;display:block;}
.logo-oxygen{
  font-size:1.9rem;
  font-weight:700;
  color:#fff;
  letter-spacing:1px;
}
nav ul{
  list-style:none;
  display:flex;
  gap:8px;
}
nav a{
  color:#fff;
  font-weight:400;
  font-size:.95rem;
  padding:8px 14px;
  border-radius:4px;
  transition:background .2s;
}
nav a:hover{background:rgba(255,255,255,.18);}
nav a.active{background:rgba(255,255,255,.28);font-weight:500;}
.nav-toggle{display:none;background:none;border:0;color:#fff;font-size:1.6rem;cursor:pointer;}

/* Page header banner (for inner pages) */
.page-banner{
  background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 100%);
  padding:50px 24px;
  text-align:center;
}
.page-banner h1{
  color:#fff;
  font-size:2.2rem;
  font-weight:600;
}
.page-banner p{
  color:#d9d3f5;
  margin-top:10px;
  font-weight:300;
}

/* Hero (home page only) */
.hero{
  background:linear-gradient(135deg,var(--navy) 0%,var(--navy-light) 100%);
  position:relative;
  overflow:hidden;
  padding:67px 24px;
}
.hero-inner{
  max-width:1100px;
  margin:0 auto;
  display:flex;
  align-items:center;
  gap:40px;
}
.hero-text{flex:1;min-width:280px;max-width:480px;position:relative;z-index:3;}
.hero-logo-img{height:64px;width:auto;margin-bottom:6px;}
.hero-text .product .h1-th{
  display:block;
  font-size:1.2rem;
  font-weight:400;
  letter-spacing:1px;
  color:#d9d3f5;
  line-height:1.4;
}
.hero-text .product{
  font-size:2.6rem;
  line-height:1.2;
  font-weight:600;
  color:#fff;
  letter-spacing:2px;
  margin-top:4px;
}
.hero-text .tagline{
  margin-top:18px;
  font-size:1.25rem;
  color:#d9d3f5;
  font-weight:300;
}
.hero-can-back{
  position:absolute;
  top:0;
  left:50%;
  height:100%;
  width:auto;
  z-index:1;
  transform:translateX(-94%) rotate(-6deg);
}
.hero-can-right{
  position:absolute;
  top:0;
  left:50%;
  height:100%;
  width:auto;
  z-index:1;
  transform:translateX(-6%) rotate(-6deg);
}

/* Sections */
section{padding:70px 0;}
.section-title{
  text-align:center;
  font-size:2.05rem;
  font-weight:600;
  color:var(--navy);
  margin-bottom:12px;
}
.section-sub{
  text-align:center;
  color:var(--muted);
  max-width:640px;
  margin:0 auto 48px;
  font-weight:300;
  font-size:1.08rem;
}

.feature-row{
  display:flex;
  align-items:center;
  gap:48px;
  margin-bottom:64px;
}
.feature-row.reverse{flex-direction:row-reverse;}
.feature-row img{flex:1;min-width:176px;max-width:248px;margin:0 auto;}
.feature-row.reverse img{min-width:151px;max-width:212px;}
.feature-text{flex:1;min-width:260px;}
.feature-text h3{
  color:var(--teal-dark);
  font-size:1.45rem;
  font-weight:600;
  margin-bottom:14px;
}
.feature-text p{color:var(--text);font-weight:300;font-size:1.08rem;}

.stats{
  display:flex;
  flex-wrap:wrap;
  gap:24px;
  justify-content:center;
  background:#fff;
  border-radius:10px;
  padding:40px 24px;
  box-shadow:0 4px 20px rgba(0,0,0,.05);
}
.stat{
  text-align:center;
  min-width:160px;
  padding:12px 20px;
}
.stat .num{
  font-size:2.2rem;
  font-weight:700;
  color:var(--teal);
}
.stat .label{color:var(--muted);font-size:.95rem;margin-top:6px;}

.cta-row{
  text-align:center;
  margin-top:56px;
}
.btn{
  display:inline-block;
  background:var(--teal);
  color:#fff;
  padding:13px 34px;
  border-radius:30px;
  font-weight:500;
  margin:0 8px;
  transition:background .2s;
}
.btn:hover{background:var(--teal-dark);}
.btn.outline{
  background:transparent;
  border:2px solid var(--teal);
  color:var(--teal-dark);
}
.btn.outline:hover{background:var(--teal);color:#fff;}

/* FAQ */
.faq-list{max-width:820px;margin:0 auto;display:grid;gap:16px;}
.faq-group-title{
  max-width:820px;
  margin:44px auto 16px;
  font-size:1.35rem;
  font-weight:600;
  color:var(--teal-dark);
}
.faq-group-title:first-child{margin-top:0;}
.faq-item{
  background:#fff;
  border-radius:10px;
  border-left:4px solid var(--teal);
  padding:22px 26px;
  box-shadow:0 4px 20px rgba(0,0,0,.05);
}
.faq-item h3{color:var(--navy);font-size:1.15rem;font-weight:600;margin-bottom:8px;}
.faq-item p{font-weight:300;font-size:1.05rem;}

/* Product spec table */
.spec-wrap{
  display:flex;
  gap:48px;
  flex-wrap:wrap;
  align-items:center;
  margin-bottom:60px;
}
.spec-wrap img{flex:1;min-width:160px;max-width:208px;margin:0 auto;}
.spec-table{flex:1;min-width:280px;}
.spec-table table{width:100%;border-collapse:collapse;}
.spec-table td{
  padding:12px 8px;
  border-bottom:1px solid #e5e7eb;
  font-size:1.08rem;
}
.spec-table td:first-child{color:var(--muted);width:45%;}
.spec-table td:last-child{font-weight:500;color:var(--navy);}

.precaution-box{
  background:#fff5f5;
  border:1px solid #fecaca;
  border-radius:10px;
  padding:30px 34px;
  max-width:720px;
  margin:0 auto;
}
.precaution-box h3{color:#b91c1c;margin-bottom:14px;font-size:1.2rem;}
.precaution-box ol{padding-left:20px;}
.precaution-box li{margin-bottom:8px;font-weight:300;font-size:1.05rem;}

/* How to use */
.howto-wrap{
  display:flex;
  align-items:center;
  gap:48px;
  flex-wrap:wrap;
}
.howto-wrap img{flex:1;min-width:120px;max-width:180px;margin:0 auto;}
.howto-steps{flex:1;min-width:280px;}
.howto-steps ol{padding-left:22px;}
.howto-steps li{margin-bottom:14px;font-weight:300;font-size:1.1rem;}
.howto-steps li::marker{color:var(--teal);font-weight:600;}

/* Dealers */
.dealer-intro{
  text-align:center;
  max-width:680px;
  margin:0 auto 50px;
  font-weight:300;
}
.dealer-list-card{
  max-width:820px;
  margin:0 auto;
  background:#fff;
  border-radius:10px;
  padding:40px;
  box-shadow:0 4px 20px rgba(0,0,0,.05);
}
.dealer-list{
  list-style:none;
  display:grid;
  grid-template-columns:repeat(auto-fit,minmax(220px,1fr));
  gap:14px;
}
.dealer-list li{
  padding:14px 18px;
  background:var(--bg);
  border-left:4px solid var(--teal);
  border-radius:6px;
  font-weight:400;
}
.dealer-cta{
  text-align:center;
  margin-top:56px;
  padding:36px;
  background:#fff;
  border-radius:10px;
  box-shadow:0 4px 20px rgba(0,0,0,.05);
}
.dealer-cta p{font-weight:300;margin-bottom:16px;}

/* Contact */
.contact-card{
  max-width:640px;
  margin:0 auto;
  background:#fff;
  border-radius:10px;
  box-shadow:0 4px 20px rgba(0,0,0,.05);
  padding:40px;
  text-align:center;
}
.map-wrap{
  max-width:640px;
  margin:28px auto 0;
  border-radius:10px;
  overflow:hidden;
  box-shadow:0 4px 20px rgba(0,0,0,.08);
  background:#fff;
}
.map-wrap iframe{display:block;width:100%;height:340px;border:0;}
.contact-card h3{color:var(--navy);font-size:1.3rem;margin-bottom:18px;}
.contact-card p{margin-bottom:8px;font-weight:300;}
.contact-card .phone{
  display:inline-block;
  margin-top:18px;
  background:var(--teal);
  color:#fff;
  padding:12px 30px;
  border-radius:30px;
  font-weight:500;
  transition:background .2s;
}
.contact-card .phone:hover{background:var(--teal-dark);}

footer{
  background:var(--navy);
  color:#cfc9e8;
  text-align:center;
  padding:26px 24px;
  font-size:.9rem;
  font-weight:300;
}
.footer-logo-img{height:56px;width:auto;margin:0 auto 6px;display:block;}

@media (max-width:768px){
  body{background-image:none;}
  body::before{
    content:"";
    position:fixed;
    top:0;
    left:0;
    width:100%;
    height:100%;
    z-index:-1;
    pointer-events:none;
    background-image:linear-gradient(rgba(247,250,251,.88),rgba(247,250,251,.88)),url('../images/hero.webp');
    background-repeat:no-repeat;
    background-position:center;
    background-size:cover,207vmin auto;
  }
  .nav-toggle{display:block;}
  .nav-wrap{flex-wrap:wrap;}
  .logo-img{height:34px;}
  .logo-oxygen{font-size:1.3rem;}
  nav{
    display:none;
    width:100%;
    order:3;
  }
  nav.open{display:block;}
  nav ul{flex-direction:column;padding:10px 0;}
  .hero-inner{flex-direction:column;text-align:center;}
  .feature-row, .feature-row.reverse{flex-direction:column;text-align:center;}
  .feature-row img{flex:none;width:248px;min-width:0;}
  .feature-row.reverse img{width:212px;}
  .howto-wrap{flex-direction:column;align-items:stretch;}
  .spec-wrap{flex-direction:column;text-align:center;}
  .hero-logo-img{height:48px;margin:0 auto 6px;}
  .hero-text .product{font-size:1.9rem;}
  .hero-img{margin-top:24px;}
  .hero-can-back{position:relative;left:50%;height:auto;width:420px;max-width:none;margin:0;transform:translateX(-50%);}
  .hero-can-right{display:none;}
}