* {
    margin: 0;
    box-sizing: border-box;
}

body {
    /* background-image: url("download (10).jpg"); */
    font-family: sans-serif;
}

.heading{
    background-color: white;
    color: black;
    font-size: 5rem;
    text-align: center;
    font-family: 'Roboto Slab', serif;
}

.flex-container-column {
    display: flex;
    flex-direction: column;
    background-color: #ced4da;
    max-width: 800px;
    margin: auto;
    text-align: right;
    padding: 20px;
}

.flex-container-row {
    display: flex;
}

.navbarBg{
    background-color: #e7ebee;
}

.button {
    flex-basis: 25%;
    color: black;
    font-size: 1.5em;
    text-align: center;
    padding: 40px;
    border: 1px solid black;
    background-color: #e3e3e3;
    cursor: pointer;
}

.double {
    flex-basis: 50%;
}

.display {
    color: white;
    width: 100%;
    padding: 10px 20px;
    background-color: black;
    border: 1px solid black;
    
    height: 15vh;
}
#displaynumber{
    font-size: 2.5rem ;
}

/* .backspace{
    flex-basis: 25%;
    color: black;
    font-size: 1.5em;
    text-align: center;
    padding: 40px;
    border: 1px solid black;
    background: #f6f6f8;
    cursor: pointer;

} */
    

.operator,
.negative,
.equals {
    background: #f6f6f8;
    color: black;
}

.card {
    box-shadow: 0 4px 8px 0 rgba(0, 0, 0, 0.2);
    border-radius: 5px;
    padding: 30px;
    /* margin-top: 20px; */
    background-color: #ced4da;
    margin: 20px auto;
}

.button:hover {
    font-weight: bold;
}

@media screen and (max-width:513px) {
    .button {
        padding: 10px;
        margin: auto;
    }
}

.history {
    width: 80%;
    margin: 30px auto 0 auto;
    overflow: scroll;
    /* color: white; */
}

table {
    border-collapse: collapse;
    border-spacing: 0;
    width: 100%;
    border: 1px solid #ddd;
}

th,
td {
    text-align: center;
    padding: 16px;
}

th {
    background-color: black;

    color: white;
}

tr:nth-child(even) {
    background-color: #f6f6f8;
}
tr:nth-child(odd) {
    background-color: #e3e3e3;
}

.center {
    margin-top: 50px;
    text-align: center;
    font-size: 5rem;
    margin: auto;
    font-family: 'Roboto Slab', serif;
    background-color: white;
    color: black;
    padding: 10px;
  }


@media screen and (max-width: 840px) {

    .button {
        padding: 20px;
    }
    .card{
        margin: 20px;
    }
    .heading{
        font-size: 4.2rem;
    }
    .center{
        font-size: 4.2rem;
    }
}
@media screen and (max-width: 513px) {
    .button {
        padding: 10px;
    }

    .history {
        width: 80%;
    }
    .heading{
        font-size: 3.5rem;
    }
    .center{
        font-size: 3.5rem;
    }

}
@media screen and (max-width: 400px) {

    .button {
        padding: 8px;
    }
    .display{
        height: 12vh;
    }
    .heading{
        font-size: 2.5rem;
    }
    .center{
        font-size: 2.5rem;
    }
    .history {
        width: 80%;
        margin: 30px auto 0 auto;
        overflow: scroll;
        /* color: white; */
    }
   
}