html{
    background-color: var(--color-bg-primary);
    box-sizing: border-box;
    line-height: 1.6rem;
    scroll-behavior: smooth;
    font-size: var(--font-size-base);
}

button{
    border: none;
}

.logo{
    font-family: "Anton", sans-serif;
    font-size: var(--font-size-logo);
}

.section{
    padding: 20px 0 60px 0;
    min-height: 100vh;
}

.section-container{
    max-width: 1500px;
    width: 95%;
    margin: 0 auto;
    background-color: var(--color-bg-white);
    border-radius: var(--radius-xl);
    /* border: var(--border-width-thick) solid var(--color-border-primary); */
    box-shadow: 0 4px 20px var(--shadow-color-blue-light);
    padding: var(--spacing-xl);
    margin-top: 15px;
    position: relative;
}

.horizontal-line{
    width: 90%;
    padding: var(--spacing-md) 0;
    margin: 0 auto;
    border-top: var(--border-width-medium) solid var(--color-black);
}



.heading-container{
    text-align: center;
    margin-bottom: 40px;
}

.heading-container h1{
    font-size: var(--font-size-section-heading);
    font-weight: 700;
    color: var(--color-purple);
    margin-bottom: 10px;
    border-bottom: var(--border-width-thick) solid var(--color-border-primary);
    padding-bottom: 10px;
    display: inline-block;
}

header{
    box-shadow: 0 2px 10px var(--shadow-color-blue-light);
    width: 100%;
    padding: 15px;
    background-color: var(--color-bg-white);
    /* border-bottom: var(--border-width-thick) solid var(--color-border-primary); */
    position: sticky;
    top: 0;
    z-index: 1000;
    transition: box-shadow 0.3s ease;
}


footer{
    display: grid;
    justify-content: center;
}


.header{
    border-bottom: none;
}

.navbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem 1.5rem;
}


.navbar .logo img{
    width: 30px;
}

.hamburger{
    display: none;
}


.bar{
    display: block;
    width:25px;
    height:3px;
    margin:5px auto;
    -webkit-transition: all 0.3s ease-in-out;
    transition: all 0.3s ease-in-out;
    background-color: #101010;
}


.nav-menu {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-item {
    margin-left: 2.5rem;

}

.nav-item > *:hover{
    border-bottom: var(--border-width-medium) solid var(--color-primary-blue-light);
}

footer{
    margin: 60px 30px 30px;
    text-align: center;
    padding: var(--spacing-md);
    color: var(--color-text-muted);
    /* border-top: var(--border-width-medium) solid var(--color-border-primary); */
}

.skills-programming-languages{
    background-color: var(--color-skill-programming);
    border: none;
}

.skills-database{
    background-color: var(--color-skill-database);
    border: none;
}

.skills-AI{
    background-color: var(--color-skill-ai);
    border: none;
}


@media only screen and (max-width: 768px) {
    .nav-menu {
        position: fixed;
        left: -100%;
        top: 5rem;
        flex-direction: column;
        background-color: var(--color-bg-white);
        width: 100%;
        border-radius: var(--radius-md);
        text-align: center;
        transition: 0.3s;
        box-shadow: 0 10px 27px var(--shadow-color-default);
    }

    .nav-menu.active {
        left: 0;
    }

    .nav-item {
        margin: 2.5rem 0;
    }



    .hamburger {
        display: block;
        cursor: pointer;
    }

    .hamburger.active .bar:nth-child(2) {
        opacity: 0;
    }

    .hamburger.active .bar:nth-child(1) {
        transform: translateY(8px) rotate(45deg);
    }

    .hamburger.active .bar:nth-child(3) {
        transform: translateY(-8px) rotate(-45deg);
    }

}

/* Back to Top Button */
.back-to-top-button {
    position: fixed;
    bottom: 20px;
    right: 20px;
    width: 50px;
    height: 50px;
    border-radius: var(--radius-circle);
    background-color: var(--color-primary-blue);
    color: var(--color-text-light);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 12px var(--shadow-color-blue-medium);
    transition: all 0.3s ease;
    opacity: 0;
    visibility: hidden;
    z-index: 999;
    border: none;
    font-size: var(--font-size-5xl);
    padding: 0;
}

.back-to-top-button.visible {
    opacity: 1;
    visibility: visible;
}

.back-to-top-button:hover {
    background-color: var(--color-primary-blue-dark);
    transform: translateY(-3px);
    box-shadow: 0 6px 16px var(--shadow-color-blue-dark);
}

.back-to-top-button:active {
    transform: translateY(-1px);
}

.back-to-top-arrow {
    display: block;
    line-height: 1;
    color: var(--color-text-light);
    font-size: var(--font-size-4xl);
    font-weight: 300;
    transform: translateY(-2px);
    filter: drop-shadow(0 1px 2px rgba(0, 0, 0, 0.2));
}

.back-to-top-text {
    position: absolute;
    bottom: 60px;
    right: 0;
    background-color: var(--color-text-primary);
    color: var(--color-text-light);
    padding: 8px 12px;
    border-radius: var(--radius-md);
    font-size: var(--font-size-sm);
    white-space: nowrap;
    opacity: 0;
    visibility: hidden;
    pointer-events: none;
    box-shadow: 0 2px 8px var(--shadow-color-default);
    transform: translateY(0);
    transition: none;
}

.back-to-top-text.show {
    animation: floatUp 2.5s ease-out forwards;
}

@keyframes floatUp {
    0% {
        opacity: 0;
        visibility: visible;
        transform: translateY(0);
    }
    10% {
        opacity: 1;
        transform: translateY(0);
    }
    90% {
        opacity: 1;
        transform: translateY(-50px);
    }
    100% {
        opacity: 0;
        visibility: hidden;
        transform: translateY(-50px);
    }
}

@media only screen and (max-width: 768px) {
    .back-to-top-button {
        width: 45px;
        height: 45px;
        bottom: 15px;
        right: 15px;
        font-size: var(--font-size-2xl);
    }
    
    .back-to-top-text {
        bottom: 55px;
        font-size: var(--font-size-xs);
        padding: 6px 10px;
    }
}