body{
    display: flex;
    flex-direction:column;
    align-items: center;
    background-color: hsl(0, 0%, 90%);
    background-image: url(night-sky-colorful-3840x2160-12510.jpg);
    background-position: center;
    background-repeat: no-repeat;
    background-size: cover;
    background-attachment: fixed;
}

#h1{
    font-size:4rem;
    font-family: Arial,sans-serif;
    color:hsl(0, 0%, 25%);
}

#container{
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 30px;
    border: 5px solid;
    border-radius: 50px;
    background-color: white ;
}

#display{
    font-size: 5rem;
    font-family: monospace;
    font-weight: bold;
    color:hsl(0, 0%, 30%);
    text-shadow: 2px 2px 2px hsl(0, 0%, 0.75%);
    margin-bottom: 25px;
}

#controls button{
    font-size: 1.5rem;
    font-weight:bold;
    padding:10px 20px;
    margin: 5px;
    min-width: 125px;
    border: none;
    border-radius: 10px;
    cursor: pointer;
    color: white;
    transition: background-color 0.5s ease;
}

#Startbtn{
    background-color: hsl(115, 100%, 40%);
}
#Startbtn:hover{
    background-color: hsl(115, 100%, 30%);
}
#Stopbtn{
    background-color: hsl(10, 90%, 50%);
}
#Stopbtn:hover{
    background-color: hsl(10, 90%, 40%);
}
#resetbtn{
    background-color: hsl(205, 90%, 60%);
}
#startbtn:hover{
    background-color: hsl(205, 90%, 50%);
}
@media (max-width: 500px) {
      #display {
        font-size: 2.2rem;
      }
      button {
        width: 100%;
        margin: 10px 0;
      }