/* ===============================
   BASE
================================ */
body {
  margin: 0;
  font-family: system-ui, -apple-system, "Segoe UI", Arial, sans-serif;
  background: #f5f7fb;
  color: #222;
}

h1, h2 {
  margin: 0 0 12px;
}

#content {
  padding: 30px 20px;
}

/* ===============================
   HERO
================================ */
.hero {
  max-width: 900px;
  margin: 30px auto 60px;
  text-align: center;
}

.hero h1 {
  font-size: 64px;
  font-weight: 900;
  color: #d83b6a;
  margin-bottom: 10px;
}

.hero-sub {
  font-size: 20px;
  color: #555;
  margin-bottom: 40px;
}

.hero-actions {
  display: flex;
  justify-content: center;
  gap: 20px;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  padding: 12px 24px;
  border-radius: 12px;
  font-size: 16px;
  font-weight: 700;
  cursor: pointer;
  transition: 0.2s;
}

.btn.primary {
  background: #d83b6a;
  color: white;
}

.btn.primary:hover {
  background: #c02f5c;
}

.btn.ghost {
  background: white;
  color: #d83b6a;
  border: 2px solid #d83b6a;
}

.btn.ghost:hover {
  background: #fff0f6;
}

/* ===============================
   INTRO
================================ */
.intro {
  max-width: 1100px;
  margin: 60px auto;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 28px;
}

.intro-card {
  background: white;
  padding: 24px;
  border-radius: 16px;
  text-align: center;
  box-shadow: 0 4px 12px rgba(0,0,0,0.06);
}

.intro-card i {
  font-size: 32px;
  color: #d83b6a;
  margin-bottom: 12px;
}

.intro-card h3 {
  font-size: 20px;
  margin-bottom: 8px;
}

.intro-card p {
  font-size: 15px;
  color: #555;
}

/* ===============================
   MENU DROPDOWN (BÉ GỌN, PHÍA PHẢI)
================================ */
.menu-dropdown {
  position: fixed;
  top: 20px;
  right: 20px;
  z-index: 999;
}

.menu-icon {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 48px;
  height: 48px;
  background: #d83b6a;
  color: white;
  border-radius: 50%;
  cursor: pointer;
  font-size: 24px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.2);
}

.menu-dropdown input[type="checkbox"] {
  display: none;
}

.menu-dropdown .menu {
  position: absolute;
  top: 60px;
  right: 0;
  display: flex;
  flex-direction: column;
  background: white;
  border-radius: 12px;
  box-shadow: 0 6px 18px rgba(0,0,0,0.2);
  padding: 10px 0;
  min-width: 180px;
  opacity: 0;
  pointer-events: none;
  transform: translateY(-10px);
  transition: all 0.3s ease;
}

.menu-dropdown input[type="checkbox"]:checked ~ .menu {
  opacity: 1;
  pointer-events: auto;
  transform: translateY(0);
}

.menu-dropdown .menu a {
  padding: 10px 20px;
  font-size: 16px;
  color: #333;
  gap: 10px;
  display: flex;
  align-items: center;
}

.menu-dropdown .menu a i {
  font-size: 18px;
  color: #d83b6a;
}

.menu-dropdown .menu a:hover {
  background: #d83b6a;
  color: white;
}

.menu-dropdown .menu a:hover i {
  color: white;
}

/* ===============================
   BLOG POST
================================ */
.post {
  max-width: 800px;
  margin: 30px auto;
  background: #fff;
  padding: 24px 28px;
  border-radius: 14px;
  box-shadow: 0 6px 20px rgba(0,0,0,0.06);
  position: relative;
}
.post-meta {
  display: flex;
  justify-content: flex-end;
  flex-wrap: wrap;
  gap: 16px;
  font-size: 14px;
  color: rgba(102, 102, 102, 0.7);
  margin-bottom: 10px;
}

.post-meta span {
  display: flex;
  align-items: center;
  gap: 6px;
}

.post-meta i {
  color: rgba(216, 59, 106, 0.5);
}

.post-meta::after {
  content: "";
  display: block;
  width: 100%;
  height: 1px;
  background: rgba(102, 102, 102, 0.2);
  margin-top: 8px;
}


/* ===============================
   MATH
================================ */
mjx-container {
  overflow-x: auto;
}

.math {
  text-align: center;
  margin: 20px 0;
}

/* ===============================
   SOLUTION
================================ */
.solution {
  margin-top: 16px;
  border-left: 4px solid #e14b7f;
  padding-left: 12px;
}

.solution button {
  background: #e14b7f;
  color: white;
  border: none;
  padding: 6px 14px;
  border-radius: 6px;
  font-weight: 600;
  cursor: pointer;
  transition: 0.2s;
}

.solution button:hover {
  opacity: 0.9;
}

.solution-content {
  display: none;
  margin-top: 10px;
}

.solution-content.open {
  display: block;
}
a {
  text-decoration: none;
  color: inherit; /* Giữ màu chữ mặc định */
}

a:hover {
  text-decoration: none; /* Không gạch chân khi hover */
}

/* ===== BUTTON TRONG TUẦN ===== */



.week-buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  margin-top: 6px;
}

.week-btn {
  display: inline-flex;
  align-items: center;
  gap: 8px;

  padding: 10px 18px;
  border-radius: 10px;

  background: #ffffff;
  border: 2px solid #cfcfcf;

  color: #333333;            /* ← xám đen */
  font-weight: 700;
  font-size: 18px;
  text-decoration: none;

  transition: all 0.25s ease;
}

.week-btn i {
  font-size: 16px;
  color: #444444;            /* ← icon hơi nhạt hơn chữ */
}

/* Hover */
.week-btn:hover {
  background: #d83b6a;
  border-color: #d83b6a;
  color: #ffffff;            /* chữ trắng */

  box-shadow: 0 8px 20px rgba(216, 59, 106, 0.45);
  transform: translateY(-2px);
}

.week-btn:hover i {
  color: #ffffff;            /* icon cũng trắng khi hover */
}

.week-btn,
.week-btn:hover {
  text-decoration: none !important;
}

.math-box {
  border: 2px solid #444;
  border-radius: 12px;
  padding: 16px 18px;
  background: #fafafa;
  margin: 20px 0;
  font-size: 16px;
}
   .social-drive {
   background: #000000;
   }
   .register-box {
   max-width: 900px;
   margin: 50px auto;
   padding: 34px 32px;
   background: linear-gradient(135deg, #ffe6ef, #fff0f6);
   border-radius: 20px;
   text-align: center;
   box-shadow: 0 12px 28px rgba(0,0,0,0.12);
   }
   .register-box h2 {
   margin-top: 0;
   color: #d83b6a;
   font-size: 30px;
   font-weight: 900;
   }
   .register-box p {
   font-size: 18px;
   margin: 16px 0 28px;
   color: #333;
   }
   .register-box a {
   display: inline-block;
   padding: 14px 34px;
   background: #d83b6a;
   color: white;
   border-radius: 40px;
   font-size: 18px;
   font-weight: 700;
   text-decoration: none;
   transition: transform 0.25s ease, box-shadow 0.25s ease;
   }
   .register-box a:hover {
   transform: translateY(-3px);
   box-shadow: 0 10px 24px rgba(216,59,106,0.45);
   }
   .year-box {
   position: relative;
   max-width: 1100px;
   margin: 70px auto;
   padding: 60px 30px 40px;
   border: 3px solid #ec5b8c;
   border-radius: 20px;
   background: #fff7fa;
   }
   /* BOX "NĂM 2025" */
   .year-title {
   position: absolute;
   top: 0;
   left: 50%;
   transform: translate(-50%, -50%);
   padding: 14px 42px;
   background: #ec5b8c; /* giữ nguyên màu như bạn đang dùng */
   color: white;
   font-size: 32px;
   font-weight: 900;
   border-radius: 20px;
   white-space: nowrap;
   /* che đường viền đi qua chính giữa */
   z-index: 2;
   }
   .contest-title-box {
   display: block;
   width: fit-content;
   margin: 0px auto 32px;   /* hạ box xuống + căn giữa */
   padding: 14px 38px;
   background: #d83b6a;
   color: white;
   font-size: 26px;
   font-weight: 700;
   border-radius: 20px;
   text-align: center;
   box-shadow: 0 10px 30px rgba(216, 59, 106, 0.4);
   }
   .contest-box {
   max-width: 900px;
   margin: 40px auto;
   padding: 30px 28px;
   background: #ffe6ef;
   border-top: 8px solid #d83b6a;
   border-radius: 0px;
   font-family: -apple-system, BlinkMacSystemFont,
   "Segoe UI", Arial,
   "Helvetica Neue",
   "Noto Sans",
   "Liberation Sans",
   sans-serif;
   color: #333;
   line-height: 1.6;
   }
   .contest-box h2 {
   text-align: center;
   color: #d83b6a;
   margin-bottom: 25px;
   font-size: 28px;
   }
   .contest-box ol {
   padding-left: 22px;
   }
   .contest-box li {
   margin-bottom: 18px;
   }
   .contest-box ul {
   margin-top: 8px;
   padding-left: 20px;
   }
   .contest-box a {
   color: #d83b6a;
   font-weight: bold;
   text-decoration: none;
   }
   .contest-box a:hover {
   text-decoration: underline;
   }
   .score-formula {
   background: white;
   padding: 10px 16px;
   border-radius: 12px;
   margin: 10px 0;
   font-weight: bold;
   text-align: center;
   color: #d83b6a;
   }
   .reward-block {
   background: #fff;
   border-radius: 14px;
   padding: 16px 20px;
   margin-top: 10px;
   }
   .reward-block p {
   margin-top: 12px;
   font-weight: bold;
   }
   header.site-header {
   background: linear-gradient(135deg, #DB3B6D, #E57195) !important;
   border-bottom: none !important;
   }
   header.site-header a.site-title {
   color: white !important;
   font-size: 30px !important;
   font-weight: 900 !important;
   letter-spacing: 1px;
   }
   header.site-header a.site-title:hover {
   text-decoration: none;
   color: #fff0f6 !important;
   }
   .stage {
   background: linear-gradient(135deg, #DB3B6D, #E57195);
   color: white;
   padding: 32px;
   border-radius: 20px;
   text-align: center;
   margin-bottom: 45px;
   box-shadow: 0 10px 24px rgba(0,0,0,0.18);
   }
   .stage h1 {
   font-size: 44px;
   font-weight: 900;
   margin: 0;
   }
   .stage p {
   font-size: 18px;
   margin-top: 10px;
   }
   .week {
   background: #F9DFE8;
   padding: 22px 26px;
   border-radius: 16px;
   margin-bottom: 32px;
   box-shadow: 0 10px 24px rgba(0,0,0,0.18);
   }
   .week h2 {
   color: #d6336c;
   font-size: 30px;
   font-weight: 800;
   margin-top: 0;
   }
   .item {
   background: white;
   padding: 18px 22px;
   border-radius: 14px;
   margin: 16px 0;
   box-shadow: 0 4px 14px rgba(0,0,0,0.10);
   font-size: 18px;
   line-height: 1.7;
   }
   .item a {
   text-decoration: none;
   color: #ff3366;
   font-weight: bold;
   }
   .item a:hover {
   text-decoration: underline;
   }

  .week-clean {
  position: relative;
  background: #FAE2E9;
  box-shadow: 0 4px 14px rgba(0,0,0,0.10);
  border-radius: 32px;
  padding: 80px 36px 36px;
  margin: 40px 0;
}

    .week-badge {
  position: absolute;
  top: 0;
  left: 50%;
  transform: translate(-50%, -50%);

  display: inline-flex;
  align-items: center;
  gap: 12px;

  padding: 8px 28px;
  background: #FAE2E9;

  border: 2px solid #333;
  border-radius: 10px;

  font-size: 22px;
  font-weight: 800;
  letter-spacing: 1px;
  color: #333;
}

.week-badge i {
  font-size: 26px;
  color: #333;
}
  .week-badge {
  top: 50px;  /* mặc định là 0 */
}
.hero-title-link {
  color: #d83b6a;   /* Màu hồng đậm như cũ */
  text-decoration: none; /* Bỏ gạch chân */
  cursor: pointer;
}

.hero-title-link:hover {
  color: #c02f5c;   /* Đổi màu khi hover nếu muốn */
}