/* ==========================
   THEME XANH GIÁO DỤC
   ========================== */
:root{
  --bg1: #0b2a22;           /* xanh thẫm */
  --bg2: #0e382b;           /* xanh đậm */
  --glow: #1b8a5a;          /* ánh xanh */
  --panel: #10382e;         /* khối */
  --slot: #0d2f26;          /* ô nhận */
  --text: #e9fff4;          /* chữ */
  --muted: #bfe8d5;         /* chữ phụ */
  --brand: #34d399;         /* emerald */
  --brand-dk: #059669;      /* đậm */
  --good: #22c55e;          /* đúng */
  --bad: #f87171;           /* sai */
  --border: #165a49;
  --radius: 16px;
  --shadow: 0 14px 38px rgba(0,0,0,.35);
  --gap: 16px;
  --maxw: 1200px;
  --transition: .22s cubic-bezier(.22,.61,.36,1);
}

/* Reset nhẹ */
*{ box-sizing: border-box; }
html, body { height: 100%; }
body{
  margin: 0;
  font-family: system-ui, -apple-system, Segoe UI, Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  color: var(--text);
  background:
    radial-gradient(1200px 600px at 50% -120px, rgba(27,138,90,.35) 0%, transparent 60%),
    linear-gradient(180deg, var(--bg2), var(--bg1));
}

/* Khung trang */
.page{ min-height: 100dvh; display: flex; flex-direction: column; }

/* Container chuẩn */
.container{ width: min(100% - 32px, var(--maxw)); margin-inline: auto; }

/* ==========================
   Header / MENU
   ========================== */
.site-header{
  position: sticky; top: 0; z-index: 20;
  background: rgba(9, 39, 30, .85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
  box-shadow: 0 8px 22px rgba(0,0,0,.25);
}
.site-header .container{
  display: flex; align-items: center; justify-content: space-between; padding: 12px 0;
}
.brand{
  color: var(--text);
  text-decoration: none;
  font-weight: 800;
  font-size: 1.1rem;
  letter-spacing: .3px;
}
.nav{ display: flex; gap: 8px; align-items: center; }
.nav-link{
  text-decoration: none;
  color: var(--muted);
  padding: 8px 12px;
  border-radius: 999px;
  border: 1px solid transparent;
  transition: var(--transition);
}
.nav-link:hover,
.nav-link.active{
  color: var(--text);
  border-color: var(--border);
  background: rgba(5, 150, 105, 0.18);
  box-shadow: 0 6px 16px rgba(5,150,105,.22);
}

/* ==========================
   AdSense slots
   ========================== */
.ad-slot{
  display: flex; align-items: center; justify-content: center;
  min-height: 90px;
  margin: 12px auto 0;
  border: 1px dashed rgba(255,255,255,.15);
  border-radius: var(--radius);
  background: #0c2f25;
  color: var(--muted);
  text-align: center;
  padding: 8px;
}
.ad-top{ margin-top: 12px; }
.ad-bottom{ margin: 18px auto; }
@media (max-width: 600px){ .ad-slot{ min-height: 50px; } }

/* ==========================
   Tiêu đề game
   ========================== */
.wideBox{
  background: linear-gradient(180deg, rgba(5,150,105,.08), transparent);
  border-bottom: 1px solid rgba(255,255,255,.06);
}
.wideBox h1{
  width: min(100% - 32px, var(--maxw));
  margin: 0 auto;
  padding: 14px 0;
  font-size: clamp(18px, 2.6vw, 28px);
  letter-spacing: .2px;
}

/* Main */
.main{ flex: 1 1 auto; display: block; }

/* Vùng nội dung */
#content{
  width: min(100% - 32px, var(--maxw));
  margin: 18px auto 28px;
  display: grid; gap: var(--gap);
}

/* Hai cột */
.two-cols{
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: var(--gap);
}

/* Nhãn cột */
.div-cota, .div-cotb{ display:flex; align-items:center; justify-content:center; }
.cota, .cotb{
  appearance: none;
  border: 1px solid var(--border);
  background: linear-gradient(180deg, #145a46, #0e3f31);
  color: var(--text);
  padding: 10px 16px;
  border-radius: 999px;
  font-weight: 800;
  letter-spacing: .3px;
  box-shadow: 0 8px 22px rgba(0,0,0,.25);
}

/* Hai khối chứa thẻ */
#cardPile, #cardSlots{
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  box-shadow: var(--shadow);
  min-height: 320px;
  display: grid;
  gap: var(--gap);
  grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
}

/* Ô con */
#cardPile > div,
#cardSlots > div{
  position: relative;
  height: 120px;
  border-radius: 14px;
  display: grid; place-items: center;
  transition: transform var(--transition), box-shadow var(--transition), border-color var(--transition), background var(--transition), filter var(--transition);
  overflow: hidden;
}

/* Lá bài bên trái */
#cardPile > div{
  background: linear-gradient(180deg, #155e4a, #0f4334);
  border: 1px solid rgba(255,255,255,.10);
  cursor: grab;
  box-shadow: 0 10px 24px rgba(0,0,0,.35);
}
#cardPile > div:active{ cursor: grabbing; }
#cardPile > div:hover{
  transform: translateY(-3px) scale(1.02);
  box-shadow: 0 18px 40px rgba(0,0,0,.40);
}

/* Ô nhận bên phải */
#cardSlots > div{
  background: var(--slot);
  border: 1px dashed rgba(255,255,255,.22);
}

/* Ảnh */
#cardPile img, #cardSlots img{
  width: 94%; height: 94%; object-fit: contain;
  filter: drop-shadow(0 6px 12px rgba(0,0,0,.35));
  pointer-events: none;
}

/* Trạng thái */
.correct{
  outline: 3px solid rgba(34,197,94,.95);
  box-shadow: 0 16px 42px rgba(34,197,94,.35);
  filter: saturate(1.1);
}
.hovered{
  border-color: rgba(52,211,153,.9) !important;
  box-shadow: inset 0 0 0 2px rgba(52,211,153,.5);
  transform: scale(1.02);
}

/* Tooltip gợi ý */
#cardPile > div::after{
  content: "Kéo sang khớp hình";
  position: absolute; bottom: 8px; left: 50%; transform: translateX(-50%);
  font-size: 11px; color: var(--muted);
  background: rgba(0,0,0,.25);
  padding: 3px 8px; border-radius: 999px;
  border: 1px solid rgba(255,255,255,.10);
  opacity: 0; transition: opacity var(--transition), transform var(--transition);
  pointer-events: none;
}
#cardPile > div:hover::after{ opacity: 1; transform: translateX(-50%) translateY(-2px); }

/* Modal hoàn thành (overlay) */
#successMessage{
  position: fixed; inset: 0; display: none; place-items: center;
  background: rgba(0,0,0,.45); z-index: 50;
}
#successMessage .modal{
  background: linear-gradient(180deg, #114a3b, #0c372c);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 20px; border-radius: 16px; text-align: center;
  min-width: min(92vw, 420px);
  box-shadow: 0 20px 50px rgba(0,0,0,.5);
}
#successMessage h2{ margin: 0 0 12px; font-size: clamp(18px, 2.2vw, 24px); }
#successMessage button{
  appearance: none; background: linear-gradient(180deg, var(--brand), var(--brand-dk));
  border: 1px solid rgba(255,255,255,.15); color: #042016;
  padding: 10px 16px; border-radius: 12px; font-weight: 800; cursor: pointer;
  transition: transform .08s ease, box-shadow var(--transition);
}
#successMessage button:hover{ transform: translateY(-1px); }
#successMessage button:active{ transform: translateY(0); }

/* Footer */
.site-footer{
  margin-top: 6px;
  border-top: 1px solid var(--border);
  background: #0a2a21;
}
.site-footer .container{
  padding: 16px 0 20px; text-align: center; color: var(--muted); font-size: 14px;
}
.footer-link{ color: var(--text); text-decoration: none; }
.footer-link:hover{ text-decoration: underline; }

/* Responsive */
@media (max-width: 900px){
  .two-cols{ grid-template-columns: 1fr; }
  #cardPile, #cardSlots{ grid-template-columns: repeat(auto-fit, minmax(110px, 1fr)); }
}
@media (max-width: 520px){
  #cardPile, #cardSlots{ grid-template-columns: repeat(2, 1fr); }
  #cardPile > div, #cardSlots > div{ height: 110px; }
}