@import url('https://fonts.googleapis.com/css2?family=Sarabun:wght@300;400;500;600;700;800&family=Noto+Sans+Thai:wght@300;400;500;600;700;800&display=swap');

:root {
  --primary:      #c0392b;
  --primary-dark: #96281b;
  --primary-glow: rgba(192,57,43,0.25);
  --gold:         #f39c12;
  --gold-light:   #fef9e7;
  --secondary:    #16a085;
  --accent:       #8e44ad;
  --danger:       #e74c3c;
  --success:      #27ae60;
  --bg:           #fdf8f0;
  --card:         #ffffff;
  --border:       #f0e6d3;
  --text:         #1a0a00;
  --muted:        #7d6b5a;
  --shadow:       0 4px 6px -1px rgba(0,0,0,0.07),0 2px 4px -1px rgba(0,0,0,0.04);
  --shadow-lg:    0 20px 40px -10px rgba(0,0,0,0.12);
  --radius:       1.25rem;
  --radius-sm:    0.75rem;
  --transition:   all 0.28s cubic-bezier(0.4,0,0.2,1);
}

*,*::before,*::after{box-sizing:border-box;margin:0;padding:0;}
html{scroll-behavior:smooth;}

body{
  font-family:'Sarabun','Noto Sans Thai',sans-serif;
  background:var(--bg);color:var(--text);
  line-height:1.7;min-height:100vh;display:flex;flex-direction:column;
}

/* ─── Header ─── */
header{
  padding:0 2rem;height:70px;display:flex;align-items:center;
  justify-content:space-between;
  background:linear-gradient(135deg,var(--primary) 0%,var(--primary-dark) 100%);
  position:sticky;top:0;z-index:999;
  box-shadow:0 4px 20px var(--primary-glow);
}
.brand{display:flex;align-items:center;gap:.75rem;text-decoration:none;}
.brand-icon{
  width:42px;height:42px;background:var(--gold);border-radius:.65rem;
  display:flex;align-items:center;justify-content:center;
  font-size:1.4rem;box-shadow:0 3px 8px rgba(0,0,0,.2);
}
.brand-name{font-size:1.25rem;font-weight:800;color:white;}
.nav-links{display:flex;align-items:center;gap:1.5rem;}
.nav-links a{color:rgba(255,255,255,.85);text-decoration:none;font-weight:600;font-size:.9rem;transition:color .2s;}
.nav-links a:hover{color:var(--gold);}

/* ─── Hero ─── */
.hero{
  background:linear-gradient(160deg,var(--primary-dark) 0%,#2c0c00 40%,#1a0900 100%);
  padding:5rem 2rem 4rem;text-align:center;position:relative;overflow:hidden;
}
.hero::before{
  content:'';position:absolute;inset:0;
  background:radial-gradient(ellipse at 30% 50%,rgba(243,156,18,.15) 0%,transparent 60%),
             radial-gradient(ellipse at 70% 20%,rgba(192,57,43,.2) 0%,transparent 50%);
  pointer-events:none;
}
.hero-badge{
  display:inline-block;background:var(--gold);color:#1a0a00;
  font-weight:700;font-size:.8rem;padding:.3rem 1rem;border-radius:2rem;
  margin-bottom:1.5rem;letter-spacing:.05em;
}
.hero h1{
  font-size:clamp(2rem,5vw,3.25rem);font-weight:800;
  color:white;margin-bottom:1.25rem;line-height:1.25;
}
.hero h1 span{color:var(--gold);}
.hero p{font-size:1.1rem;color:rgba(255,255,255,.75);max-width:620px;margin:0 auto;}

/* ─── Main ─── */
main{flex:1;padding:3rem 1.5rem;max-width:1050px;margin:0 auto;width:100%;}

/* ─── Calc Card ─── */
.calc-card{
  background:var(--card);border:1px solid var(--border);
  border-radius:var(--radius);padding:3rem 3rem 2.5rem;
  box-shadow:var(--shadow-lg);position:relative;overflow:hidden;margin-bottom:3rem;
}
.calc-card::before{
  content:'';position:absolute;top:0;left:0;right:0;height:5px;
  background:linear-gradient(90deg,var(--primary),var(--gold),var(--secondary));
}
.calc-title{
  font-size:1rem;font-weight:700;color:var(--muted);text-align:center;
  margin-bottom:2.5rem;letter-spacing:.05em;text-transform:uppercase;
}

/* ─── Fraction Inputs ─── */
.fraction-grid{
  display:flex;align-items:center;justify-content:center;
  gap:2rem;flex-wrap:wrap;margin-bottom:2.5rem;
}
.fraction-group{display:flex;align-items:center;gap:.65rem;}
.num-label{
  font-size:.65rem;font-weight:700;color:var(--muted);
  text-transform:uppercase;letter-spacing:.05em;text-align:center;margin-bottom:.25rem;
}
.input-stack{display:flex;flex-direction:column;align-items:center;}

input[type="number"]{
  width:5rem;height:4.5rem;border:2.5px solid var(--border);
  border-radius:.85rem;text-align:center;font-size:1.6rem;
  font-weight:700;font-family:'Sarabun',sans-serif;
  background:#fffdf7;color:var(--text);transition:var(--transition);
  -moz-appearance:textfield;
}
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button{-webkit-appearance:none;}
input[type="number"]:focus{
  border-color:var(--primary);outline:none;
  box-shadow:0 0 0 4px var(--primary-glow);
  transform:translateY(-2px);background:white;
}
.whole-input{width:4rem;}
.frac-line{
  width:5rem;height:3px;
  background:linear-gradient(90deg,var(--primary),var(--gold));
  border-radius:2px;margin:.3rem 0;
}
.div-op{font-size:3rem;font-weight:900;color:var(--primary);padding:0 .5rem;line-height:1;}

/* ─── Buttons ─── */
.actions{display:flex;gap:1rem;justify-content:center;flex-wrap:wrap;margin-top:2rem;}
.btn{
  padding:.9rem 2.2rem;border:none;border-radius:.85rem;
  font-family:'Sarabun',sans-serif;font-size:1rem;font-weight:700;
  cursor:pointer;transition:var(--transition);display:inline-flex;align-items:center;gap:.5rem;
}
.btn-primary{
  background:linear-gradient(135deg,var(--primary),var(--primary-dark));
  color:white;box-shadow:0 4px 12px var(--primary-glow);
}
.btn-primary:hover{transform:translateY(-3px);box-shadow:0 8px 24px var(--primary-glow);}
.btn-gold{
  background:linear-gradient(135deg,var(--gold),#e67e22);
  color:white;box-shadow:0 4px 12px rgba(243,156,18,.3);
}
.btn-gold:hover{transform:translateY(-3px);}
.btn-ghost{background:transparent;border:2px solid var(--border);color:var(--muted);}
.btn-ghost:hover{border-color:var(--muted);background:var(--bg);}

/* ─── Result ─── */
.result-section{
  display:none;margin-top:3rem;padding-top:3rem;
  border-top:2px dashed var(--border);
  animation:fadeUp .45s ease-out both;
}
@keyframes fadeUp{
  from{opacity:0;transform:translateY(18px);}
  to{opacity:1;transform:translateY(0);}
}
.result-answer{text-align:center;margin-bottom:2.5rem;}
.answer-label{
  font-size:.8rem;font-weight:700;color:var(--muted);
  letter-spacing:.07em;text-transform:uppercase;margin-bottom:.5rem;
}
.answer-value{font-size:4rem;font-weight:800;color:var(--primary);line-height:1.1;}

.step-grid{display:flex;flex-direction:column;gap:1.25rem;}
.step-card{
  background:var(--bg);border:1.5px solid var(--border);
  border-radius:var(--radius-sm);padding:1.75rem 1.75rem 1.75rem 3.5rem;
  position:relative;
}
.step-badge{
  position:absolute;left:-1px;top:50%;transform:translateY(-50%);
  width:8px;height:50%;min-height:40px;border-radius:0 4px 4px 0;
}
.step-badge.s1{background:var(--primary);}
.step-badge.s2{background:var(--gold);}
.step-badge.s3{background:var(--secondary);}
.step-badge.s4{background:var(--accent);}
.step-label{
  font-size:.72rem;font-weight:800;color:var(--muted);
  letter-spacing:.08em;text-transform:uppercase;margin-bottom:.5rem;
}
.step-math{
  font-size:1.4rem;font-weight:700;color:var(--text);
  display:flex;align-items:center;gap:1rem;flex-wrap:wrap;
}

/* ─── Visualizer ─── */
.visualizer-wrap{
  display:none;margin-top:2rem;padding:1.5rem;
  background:var(--bg);border-radius:var(--radius-sm);border:1px solid var(--border);
}
.vis-label{
  font-size:.72rem;font-weight:700;color:var(--muted);
  letter-spacing:.06em;text-transform:uppercase;margin-bottom:1.25rem;
}
.vis-row{display:flex;align-items:center;gap:1rem;margin-bottom:.75rem;}
.vis-name{width:90px;font-size:.85rem;font-weight:700;color:var(--muted);}
.bar-track{flex:1;height:18px;background:var(--border);border-radius:9px;overflow:hidden;}
.bar-fill{height:100%;border-radius:9px;transition:width .7s cubic-bezier(.175,.885,.32,1.275);}
.bar-a{background:linear-gradient(90deg,var(--primary),var(--gold));}
.bar-b{background:linear-gradient(90deg,var(--secondary),#1abc9c);}

/* ─── Quiz ─── */
.quiz-section{
  background:white;border:1px solid var(--border);
  border-radius:var(--radius);padding:2.5rem;margin-bottom:3rem;
  position:relative;overflow:hidden;
}
.quiz-section::before{
  content:'';position:absolute;top:0;left:0;right:0;height:5px;
  background:linear-gradient(90deg,var(--gold),var(--primary));
}
.quiz-section h2{font-size:1.5rem;font-weight:800;margin-bottom:.5rem;}
.level-tabs{display:flex;gap:.5rem;margin:1.25rem 0;flex-wrap:wrap;}
.level-btn{
  padding:.5rem 1.25rem;border-radius:2rem;border:2px solid var(--border);
  background:var(--bg);font-family:'Sarabun',sans-serif;font-size:.9rem;
  font-weight:700;cursor:pointer;transition:var(--transition);color:var(--muted);
}
.level-btn.active{background:var(--primary);border-color:var(--primary);color:white;}
.level-btn:hover:not(.active){border-color:var(--primary);color:var(--primary);}

.quiz-problem-box{
  font-size:2.75rem;font-weight:800;color:var(--text);text-align:center;
  margin:1.5rem 0;padding:1.5rem;background:var(--bg);
  border-radius:var(--radius-sm);border:1px solid var(--border);
}
.quiz-answer-row{display:flex;align-items:center;justify-content:center;gap:.75rem;margin-bottom:1.25rem;}
.quiz-answer-row input{width:5.5rem;height:4rem;font-size:1.5rem;}
.quiz-slash{font-size:2.5rem;font-weight:800;color:var(--muted);}
.quiz-feedback{
  min-height:2rem;font-size:1.1rem;font-weight:700;text-align:center;
  padding:.75rem;border-radius:var(--radius-sm);transition:var(--transition);
}
.feedback-correct{background:#d5f5e3;color:#1e8449;}
.feedback-wrong{background:#fadbd8;color:#922b21;}

/* ─── Content / SEO ─── */
.content-section{margin-bottom:4rem;}
.content-section h2{
  font-size:1.75rem;font-weight:800;color:var(--primary);
  margin-bottom:1.5rem;padding-bottom:.75rem;
  border-bottom:3px solid var(--gold-light);
}
.content-grid{
  display:grid;grid-template-columns:repeat(auto-fit,minmax(300px,1fr));
  gap:1.5rem;margin-bottom:2rem;
}
.info-card{
  background:white;border:1px solid var(--border);
  border-radius:var(--radius-sm);padding:1.75rem;
}
.info-card h3{font-size:1.05rem;font-weight:800;color:var(--primary);margin-bottom:.75rem;}
.info-card p{color:var(--muted);font-size:.95rem;line-height:1.8;}

.steps-list{list-style:none;display:flex;flex-direction:column;gap:1rem;counter-reset:step;}
.steps-list li{
  counter-increment:step;background:white;border:1px solid var(--border);
  border-radius:var(--radius-sm);padding:1.1rem 1.1rem 1.1rem 4.25rem;
  position:relative;color:var(--muted);font-size:.95rem;
}
.steps-list li::before{
  content:counter(step);position:absolute;left:1.1rem;top:50%;
  transform:translateY(-50%);width:2rem;height:2rem;
  background:var(--primary);color:white;border-radius:50%;
  display:flex;align-items:center;justify-content:center;
  font-weight:800;font-size:.9rem;
}

.word-problem{
  background:linear-gradient(135deg,var(--gold-light) 0%,#fdebd0 100%);
  border-left:5px solid var(--gold);padding:2rem;
  border-radius:0 var(--radius-sm) var(--radius-sm) 0;margin:2rem 0;
}
.word-problem .wp-header{font-weight:800;color:var(--text);font-size:1.1rem;margin-bottom:1rem;}
.word-problem p{color:#6e4c20;line-height:1.9;}

.glossary-grid{
  display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:1.25rem;
}
.glossary-card{
  background:white;border:1px solid var(--border);
  border-radius:var(--radius-sm);padding:1.35rem;border-top:3px solid var(--gold);
}
.glossary-term{font-weight:800;color:var(--primary);display:block;margin-bottom:.5rem;}

.faq-list{display:flex;flex-direction:column;gap:1rem;}
.faq-item{background:white;border:1px solid var(--border);border-radius:var(--radius-sm);overflow:hidden;}
.faq-q{
  padding:1.25rem 1.5rem;font-weight:700;cursor:pointer;
  display:flex;justify-content:space-between;align-items:center;
  color:var(--text);user-select:none;gap:1rem;
}
.faq-q:hover{background:var(--bg);}
.faq-q .icon{color:var(--primary);font-size:1.2rem;transition:transform .3s;flex-shrink:0;}
.faq-item.open .faq-q .icon{transform:rotate(45deg);}
.faq-a{
  display:none;padding:0 1.5rem 1.25rem;color:var(--muted);
  font-size:.95rem;line-height:1.85;border-top:1px solid var(--border);padding-top:1rem;
}
.faq-item.open .faq-a{display:block;}

/* ─── Footer ─── */
footer{
  background:linear-gradient(135deg,#1a0a00 0%,#2c0c00 100%);
  color:rgba(255,255,255,.8);padding:3rem 2rem;text-align:center;
}
.footer-nav{display:flex;justify-content:center;gap:2rem;margin-bottom:1.5rem;flex-wrap:wrap;}
.footer-nav a{color:rgba(255,255,255,.6);text-decoration:none;font-size:.9rem;font-weight:600;transition:color .2s;}
.footer-nav a:hover{color:var(--gold);}
footer p{font-size:.85rem;color:rgba(255,255,255,.4);margin-top:.75rem;}

/* ─── Print ─── */
@media print{
  header,footer,.quiz-section,.hero,.actions,.content-section{display:none !important;}
  main{padding:0;}
  .calc-card{box-shadow:none;border:none;}
  .result-section{display:block !important;}
}

/* ─── Mobile ─── */
@media(max-width:640px){
  .hero{padding:3rem 1.25rem 2.5rem;}
  .calc-card{padding:1.75rem;}
  .fraction-grid{gap:1.25rem;}
  input[type="number"]{width:4rem;height:4rem;font-size:1.3rem;}
  .answer-value{font-size:2.75rem;}
  .nav-links{gap:.75rem;}
  .nav-links a{font-size:.8rem;}
}