<style>
body {
  background-color: #fcf5f5;
  background-image: url("Large-Triangles.svg");
}

header {
  color: Blue;
  text-align: center;
  background-color: white;
  padding: 20px;
  border-radius: 70px;
  opacity: 0.6;
}

#science1, #religious, #science3, #social, #mathschoice,
#maths1, #maths2, #spelling1, #learning_games {
  padding: 30px;
  border-style: double;
  margin: 0 90px;
  border-radius: 50px;
  font-size: 30px;
  text-align: center;
}

#science1 { background-color: yellow; }
#religious { background-color: limegreen; }
#science3 { background-color: white; }
#social { background-color: lightblue; }
#mathschoice { background-color: #e5ed47; }
#maths1 { background-color: #8dbdd9; }
#maths2 { background-color: #f2b6b6; }
#spelling1 { background-color: lightgrey; }
#learning_games { background-color: lightgreen; }

/* Tablets */
@media (max-width: 800px) {
  #spelling1, #MathsandLanguage, #upload, #calculator, #maths1 {
    background-color: white;
    padding: 30px;
    border-style: double;
    margin: 0 60px;
    border-radius: 50px;
    font-size: 30px;
    text-align: center;
  }

  #div {
    color: blue;
    background-color: yellow;
    font-size: 25px;
  }

  #billboard, #footer {
    text-align: center;
  }

  #spelling {
    width: 170px;
    border: 15px solid green;
    padding: 50px;
    margin: 20px;
    font-size: 16px;
    font-weight: bold;
  }
}

/* Smartphones */
@media (max-width: 600px) {
  #spelling1, #science1, #maths2, #calculator, #social, #religious {
    background-color: lightgrey;
    padding: 5px;
    border-style: double;
    margin: 0 30px;
    border-radius: 50px;
    font-size: 20px;
    text-align: center;
  }

  marquee {
    color: blue;
    background-color: yellow;
    font-size: 25px;
  }

  #billboard, #footer {
    text-align: center;
  }

  #iframe {
    text-align: center;
  }
}
/* NAVBAR BASE */
.navbar {
  overflow: hidden;
  background-color: #000; /* Black navbar */
  font-family: Arial;
}

.navbar a {
  float: left;
  font-size: 16px;
  color: white !important;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
}

.navbar a:hover { background-color: #444; }

/* DROPDOWN PARENT CONTAINERS */
.dropdown, .dropdown2, .dropdown3, .dropdown4, .dropdown5 {
  float: right;
  overflow: hidden;
}

/* DROPDOWN BUTTONS */
.dropbtn, .dropbtn2, .dropbtn3, .dropbtn4, .dropbtn5 {
  font-size: 16px;
  border: none;
  outline: none;
  color: white;
  padding: 14px 16px;
  background-color: black;
  font-family: inherit;
  margin: 0;
}

/* DROPDOWN HOVER COLORS */
.dropdown:hover .dropbtn { background-color: red; }
.dropdown2:hover .dropbtn2 { background-color: blue; }
.dropdown3:hover .dropbtn3 { background-color: green; }
.dropdown4:hover .dropbtn4,
.dropdown5:hover .dropbtn5 { background-color: orange; }

/* DROPDOWN CONTENT BOXES (Black background + White links) */
.dropdown-content, .dropdown-content2, .dropdown-content3,
.dropdown-content4, .dropdown-content5 {
  display: none;
  position: absolute;
  background-color: #000 !important; /* Black background */
  min-width: 160px;
  box-shadow: 0 8px 16px rgba(0,0,0,0.35);
  z-index: 1;
  opacity: 1 !important; /* Ensure visible */
}

.dropdown-content a, .dropdown-content2 a, .dropdown-content3 a,
.dropdown-content4 a, .dropdown-content5 a {
  float: none;
  color: #fff !important; /* White text */
  padding: 12px 16px;
  text-decoration: none;
  display: block;
  text-align: left;
  background: transparent;
}

.dropdown-content a:hover,
.dropdown-content2 a:hover,
.dropdown-content3 a:hover,
.dropdown-content4 a:hover,
.dropdown-content5 a:hover {
  background-color: #111; /* Dark hover */
  color: #fff !important;
}

/* SHOW DROPDOWN ON HOVER */
.dropdown:hover .dropdown-content,
.dropdown2:hover .dropdown-content2,
.dropdown3:hover .dropdown-content3,
.dropdown4:hover .dropdown-content4,
.dropdown5:hover .dropdown-content5 {
  display: block;
}

/* RESPONSIVE NAVBAR FOR MOBILE */
@media screen and (max-width: 600px) {
  .navbar {
    background-color: #000;
    padding: 0;
  }

  .navbar a,
  .dropdown,
  .dropdown2,
  .dropdown3,
  .dropdown4,
  .dropdown5 {
    float: none;
    display: block;
    width: 100%;
    text-align: left;
    padding: 12px;
    font-size: 14px;
    border-bottom: 1px solid #444;
    color: white !important;
  }

  .navbar a:hover {
    background-color: #222;
  }

  .dropdown-content,
  .dropdown-content2,
  .dropdown-content3,
  .dropdown-content4,
  .dropdown-content5 {
    position: static;
    box-shadow: none;
    background-color: #000 !important;
  }

  .dropdown-content a,
  .dropdown-content2 a,
  .dropdown-content3 a,
  .dropdown-content4 a,
  .dropdown-content5 a {
    color: #fff !important;
    font-size: 14px;
    padding: 10px 16px;
  }

  .dropdown-content a:hover {
    background-color: #333;
  }
}
<style>