style(dark).css

:root {
  --dark-body: #4d4c5a;
  --dark-main: #141529;
  --dark-second: #79788c;
  --dark-hover: #323048;
  --dark-text: #f8fbff;
  --dark-back: rgb(12, 10, 10);

  --light-body: #f3f8fe;
  --light-main: #fdfdfd;
  --light-second: #c3c2c8;
  --light-hover: #edf0f5;
  --light-text: #151426;
  --light-back: yellowgreen;

  --blue: #0000ff;
  --white: #fff;

  --shadow: rgba(100, 100, 111, 0.2) 0px 7px 29px 0px;

  --font-family: cursive;
}
.dark {
  --bg-body: var(--dark-body);
  --bg-main: var(--dark-main);
  --bg-second: var(--dark-second);
  --color-hover: var(--dark-hover);
  --color-txt: var(--dark-text);
  --color-back: var(--dark-back);
}

.light {
  --bg-body: var(--light-body);
  --bg-main: var(--light-main);
  --bg-second: var(--light-second);
  --color-hover: var(--light-hover);
  --color-txt: var(--light-text);
  --color-back: var(--light-back);
}
html,
body {
    height: 100vh;
    display: grid;
    font-family: var(--font-family);
    background-color: var(--bg-body);
    background: var(--color-back);
    
    
}
.container{
  font-family: arial;
  font-weight: bold;
  color: #000000;
  border: 1px solid #000000;
  width: 340px;
  padding: 10px;
  text-align: center;
  -webkit-border-radius: 10px;
  -moz-border-radius: 10px;
  border-radius: 10px;
}
.title {
    font-family:'Courier New', Courier, monospace;  
    color: black;
    font-weight: solid;
    text-align: center;
    position: absolute;
    top: 40%;
    left: 40%;
    font-size: 30px;
    
  }
.button {
    font-family: 'Courier New', Courier, monospace;  
    text-align: center;
    position: absolute;
    font-size: 15px;
    top: 55%;
    left: 30%;
    
  }
.btn {
    color: black;
    border: 1px solid black;
    padding: 10px 30px; 
    transition: 0.6s ease;
}
.btn:hover {
    background-color: black;
    color: white;
  }
  .toggle {
    margin-left: 650px;
    margin-top: 500px;
    position: center;
    display: flex;
}

.toggle span {
    margin-right: 10px;
    
    color: var(--color-txt);
}

.dark-mode-switch {
    position: relative;
    width: 48px;
    height: 25px;
    border-radius: 14px;
    background-color: rgb(65, 65, 94);
    cursor: pointer;
}

.dark-mode-switch-ident {
    width: 21px;
    height: 21px;
    border-radius: 50%;
    background-color: rgb(143, 66, 66);
    position: absolute;
    top: 2px;
    left: 2px;
    transition: left 0.2s ease-in-out;
}

.dark .dark-mode-switch .dark-mode-switch-ident {
    top: 2px;
    left: calc(2px + 50%);
}

header {
    background-image: url(../Background.jpg);
    height: 100vh;
    background-size: cover;
    background-position: center;
  }