* {
    box-sizing: border-box;
    margin: 0;
    color: silver;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

html, body {
    height: 100%;
    background-color: beige;
}

#nav-header {
    display: flex;
    flex-direction: column;
    height: 100px;
    background-color: black;
    padding-top: 25px;
    color: white;
    text-align: center;
    font-family: 'Franklin Gothic Medium', 'Arial Narrow', Arial, sans-serif;
}

.nav-bar {
    background-color: black;
    height: 50px;
    display: flex;
    align-items: center;
}

.tabs {
    display: flex;
}

    .tabs p {
        margin: 10px 0;
    }

    .tabs button.active {
        color: yellow;
        transform: scale(1.1);
    }

.tablinks {
    color: silver;
    text-decoration: none;
    padding: 14px 16px;
    font-size: 17px;
    margin: 10px 0;
}

.back {
    margin: 10px 550px 10px 0;
}

.btn {
    text-align: left;
    display: inline-block;
    padding: 0px 20px;
    text-decoration: none;
    background-color: transparent;
    border: none;
    transition: all ease 0.5s;
}

.btn:hover {
    color: yellow;
    cursor: pointer;
    transform: scale(1.1);
}

.tabcontent {
    display: none;
    padding: 6px 12px;
}

.certificate-container {
    display: flex;
    flex-direction: column;
    padding-top: 10px;
    margin: 20px 0;
}

.certificate{
    margin: 30px auto;
    height: 70vh;
    width: 50%;
    border: 1px solid black;
    border-radius: 8px;
    z-index: 1;
}

@media screen and (max-width: px) {
    #nav-header {
        height: auto;
        padding: 12px;
    }

    .nav-bar {
        height: auto;
        flex-wrap: wrap;
        gap: 8px;
        justify-content: center;
    }

    .tabs {
        flex-wrap: wrap;
        gap: 8px;
    }

        .tabs p {
            display: none;
        }

    .tablinks, .back {
        padding: 10px 12px;
        font-size: 16px;
    }

    .btn {
        min-height: 44px;
    }

    .tabcontent {
        padding: 12px;
    }

    .certificate-container {
        margin: 10px 0;
        padding-top: 0;
    }

    .certificate {
        width: 100%;
        height: auto;
        max-height: 70vh;
    }
}

@media screen and (max-width: 768px) {
    #nav-header {
        height: auto;
        padding: 12px 16px;
        background-color: transparent;
        color: black;
        text-align: left;
        align-items: flex-start;
    }

    .nav-bar {
        height: auto;
        flex-wrap: wrap;
        gap: 8px;
        justify-content: flex-start;
        background-color: inherit;
    }

    .back {
        margin: 10px 0;
    }

    .tabs {
        flex-wrap: wrap;
        gap: 8px;
    }

        .tabs p {
            display: none;
        }

    .tablinks,
    .back {
        padding: 10px 12px;
        font-size: 16px;
    }

    .btn {
        min-height: 44px;
        padding: 0 12px;
    }

    .tabcontent {
        padding: 12px;
    }

    .certificate-container {
        margin: 10px 0;
        padding-top: 0;
    }

    .certificate {
        width: 100%;
        max-width: 100%;
        height: auto;
        max-height: 70vh;
    }
}