/* =========================================================
   MAINPAGE - ĐỒNG BỘ VỚI GAMEPAGE
   Style: pixel survival / dark chest UI / vàng nâu
   Giữ nguyên HTML/PHP, chỉ thay mainpage.css
   ========================================================= */

* {
  box-sizing: border-box;
}

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  font-family: "Pixelify Sans", sans-serif;
  color: #fff1c7;

  background:
    linear-gradient(rgba(0, 0, 0, 0.42), rgba(0, 0, 0, 0.72)),
    url("../image/mainBG.png");

  background-size: cover;
  background-position: bottom;
  background-repeat: no-repeat;
  background-attachment: fixed;
}

.teacher-page {
  margin: 0;
  font-family: "Pixelify Sans", sans-serif;
  color: #fff1c7;

  background:
    linear-gradient(rgba(0, 0, 0, 0.42), rgba(0, 0, 0, 0.72)),
    url("../image/teacher_background.jpg");

  background-size: cover;
  background-position: bottom;
  background-repeat: no-repeat;
  background-attachment: fixed;
}

/* ================= HEADER ================= */

header {
  width: 560px;
  position: sticky;
  top: 14px;
  left: 50%;
  transform: translateX(-50%);
  z-index: 1000;

  padding: 14px 30px;
  border-radius: 14px;

  display: flex;
  justify-content: space-between;
  align-items: center;

  background: linear-gradient(
    145deg,
    rgba(24, 17, 11, 0.92),
    rgba(5, 5, 5, 0.88)
  );

  border: 3px solid #5c3a1c;

  backdrop-filter: blur(8px);

  box-shadow:
    inset 0 0 16px rgba(255, 210, 120, 0.08),
    0 8px 20px rgba(0, 0, 0, 0.55);
}

.headerVT {
  text-decoration: none;
}

header h1 {
  margin: 0;
  font-size: 28px;
  color: #ffd76a;

  text-shadow:
    2px 2px 0 #000,
    -1px -1px 0 rgba(255, 255, 255, 0.45);
}

/* ================= NAV ================= */

nav ul {
  list-style: none;
  margin: 0;
  padding: 0;

  display: flex;
  gap: 16px;
}

nav a {
  text-decoration: none;
  color: #fff1c7;

  font-size: 16px;
  font-weight: bold;

  padding: 8px 12px;
  border-radius: 8px;

  text-shadow: 2px 2px 0 #000;
  transition: 0.18s;
}

nav a:hover {
  background: linear-gradient(#ffd76a, #b97a25);
  color: #20140b;

  text-shadow: -1px -1px 0 rgba(255, 255, 255, 0.45);

  box-shadow:
    0 0 14px rgba(255, 218, 77, 0.45),
    0 4px 0 rgba(0, 0, 0, 0.4);
}

/* ================= MAIN ================= */

main {
  text-align: center;
  margin-top: 110px;
}

#home {
  min-height: 100vh;

  display: flex;
  flex-direction: column;
  justify-content: center;
  align-items: center;

  margin-top: -110px;
  padding-top: 80px;
}

/* ================= WELCOME TEXT ================= */

.welcome {
  margin: 18px 0;
  font-size: clamp(48px, 7vw, 90px);
  line-height: 1.08;

  color: #e3a805;

  text-shadow:
    4px 4px 0 #1a1008,
    -2px -2px 0 #fff1c7,
    0 0 18px rgba(255, 214, 87, 0.45);
}

.welcome a {
  color: #ffd76a;
  text-decoration: none;
  transition: 0.2s;

  text-shadow:
    4px 4px 0 #1a1008,
    -2px -2px 0 #fff1c7;
}

.welcome a:hover {
  color: #ffb732;
  filter: brightness(1.15);
}

/* ================= PLAY FORM ================= */

.divPlay {
  margin-top: 30px;
  padding: 22px 32px;

  font-size: 30px;
  color: #ffd76a;

  background: linear-gradient(
    145deg,
    rgba(24, 17, 11, 0.82),
    rgba(5, 5, 5, 0.78)
  );

  border: 3px solid #5c3a1c;
  border-radius: 16px;

  backdrop-filter: blur(6px);

  text-shadow:
    2px 2px 0 #000,
    -1px -1px 0 rgba(255, 255, 255, 0.45);

  box-shadow:
    inset 0 0 16px rgba(255, 210, 120, 0.08),
    0 10px 24px rgba(0, 0, 0, 0.55);
}

.exam-code-container {
  margin: 0 0 16px 0;
  display: flex;
  justify-content: center;
}

.exam-code-container input[type="text"] {
  width: 190px;
  padding: 12px 16px;

  border: 3px solid #9b6a35;
  border-radius: 10px;

  font-size: 17px;
  font-family: "Pixelify Sans", sans-serif;
  text-align: center;

  color: #fff1c7;
  background: rgba(32, 18, 10, 0.92);

  outline: none;

  box-shadow:
    inset 0 0 12px rgba(0, 0, 0, 0.7),
    0 0 12px rgba(255, 218, 77, 0.18);

  transition: 0.22s;
}

.exam-code-container input[type="text"]::placeholder {
  color: rgba(255, 241, 199, 0.72);
}

.exam-code-container input[type="text"]:focus {
  width: 250px;
  border-color: #ffd76a;

  background: rgba(42, 22, 10, 0.96);

  box-shadow:
    inset 0 0 12px rgba(0, 0, 0, 0.72),
    0 0 18px rgba(255, 218, 77, 0.55);
}

/* ================= BUTTON ================= */

button {
  font-family: "Pixelify Sans", sans-serif;
  font-weight: bold;

  background: linear-gradient(#ffd76a, #b97a25);
  color: #20140b;

  padding: 14px 38px;
  margin-bottom: 12px;

  font-size: 22px;

  border: 3px solid #2a1a0d;
  border-radius: 8px;

  cursor: pointer;

  box-shadow:
    5px 5px 0 #120b06,
    0 0 16px rgba(255, 218, 77, 0.38);

  text-shadow: -1px -1px 0 rgba(255, 255, 255, 0.55);

  transition: 0.16s;
}

button:hover {
  background: linear-gradient(#fff06d, #d99028);

  transform: translateY(-3px);

  box-shadow:
    5px 8px 0 #120b06,
    0 0 22px rgba(255, 218, 77, 0.58);
}

button:active {
  transform: translateY(2px);
  box-shadow:
    2px 2px 0 #120b06,
    0 0 12px rgba(255, 218, 77, 0.38);
}

/* ================= MODE SELECT ================= */

select {
  padding: 10px 32px 10px 14px;

  border-radius: 10px;
  border: 3px solid #9b6a35;

  background: linear-gradient(#fff1c7, #d9ad5c);

  color: #20140b;

  font-family: "Pixelify Sans", sans-serif;
  font-size: 16px;
  font-weight: bold;

  cursor: pointer;

  appearance: none;
  -webkit-appearance: none;
  -moz-appearance: none;

  box-shadow:
    3px 3px 0 #120b06,
    0 0 12px rgba(255, 218, 77, 0.28);
}

select:hover {
  border-color: #ffd76a;
  background: linear-gradient(#fff4d2, #e6bd68);
}

option {
  background-color: #2b1b10;
  color: #fff1c7;
}

option:checked {
  background-color: #b97a25;
  color: #20140b;
}

/* ================= ABOUT US ================= */

#aboutus {
  min-height: 100vh;

  display: flex;
  padding: 120px 40px 200px;
  justify-content: center;
  align-items: flex-start;
  gap: 34px;
}

.card {
  width: 350px;
  height: auto;

  padding: 20px;
  margin: 0 10px 10px;

  display: flex;
  flex-direction: column;
  align-items: center;

  background: linear-gradient(
    145deg,
    rgba(24, 17, 11, 0.9),
    rgba(5, 5, 5, 0.84)
  );

  border: 3px solid #5c3a1c;
  border-radius: 16px;

  backdrop-filter: blur(8px);

  color: #fff1c7;

  box-shadow:
    inset 0 0 16px rgba(255, 210, 120, 0.08),
    0 10px 24px rgba(0, 0, 0, 0.55);
}

.card:hover {
  border-color: #ffd76a;

  box-shadow:
    inset 0 0 16px rgba(255, 210, 120, 0.08),
    0 0 22px rgba(255, 218, 77, 0.3),
    0 10px 24px rgba(0, 0, 0, 0.55);
}

.card-title {
  font-size: 28px;
  color: #ffd76a;
  margin-bottom: 12px;

  text-shadow:
    2px 2px 0 #000,
    -1px -1px 0 rgba(255, 255, 255, 0.45);
}

.card p {
  font-size: 17px;
  line-height: 1.45;
  text-shadow: 2px 2px 0 #000;
}

img {
  width: 100%;
  height: auto;

  border-radius: 12px;
  border: 3px solid #2a1a0d;

  box-shadow:
    inset 0 0 16px rgba(0, 0, 0, 0.5),
    0 6px 14px rgba(0, 0, 0, 0.45);
}

iframe {
  width: 100%;
  height: 200px;

  border: 3px solid #2a1a0d;
  border-radius: 12px;

  box-shadow: 0 6px 14px rgba(0, 0, 0, 0.45);
}

/* ================= FOOTER ================= */

footer {
  margin-top: 100px;
  margin-bottom: 0;
  padding: 20px;

  text-align: center;

  background: linear-gradient(
    145deg,
    rgba(24, 17, 11, 0.92),
    rgba(5, 5, 5, 0.88)
  );

  border-top: 3px solid #5c3a1c;

  color: #fff1c7;

  text-shadow: 2px 2px 0 #000;
}

/* ================= RESPONSIVE ================= */

@media (max-width: 1000px) {
  header {
    width: calc(100% - 30px);
    padding: 12px 18px;
  }

  header h1 {
    font-size: 22px;
  }

  nav ul {
    gap: 8px;
  }

  nav a {
    font-size: 14px;
    padding: 6px 8px;
  }

  .welcome {
    font-size: 46px;
  }

  #aboutus {
    flex-direction: column;
    align-items: center;
    padding-top: 80px;
  }

  .card {
    width: min(90%, 420px);
  }
}