/* ==========================================================================
   Reset & Base Styles
   ========================================================================== */
:root {
    --primary-color: #3498db;
    --secondary-color: #2c3e50;
    --text-color: #333;
    --bg-color: #fff;
    --card-bg: #f8f9fa;
    --border-color: #ddd;
    --shadow-color: rgba(0,0,0,0.1);
    --hover-shadow: rgba(0,0,0,0.15);
}

[data-theme="dark"] {
    --primary-color: #4fa3e0;
    --secondary-color: #34495e;
    --text-color: #f0f0f0;
    --bg-color: #1a1a1a;
    --card-bg: #2d2d2d;
    --border-color: #404040;
    --shadow-color: rgba(0,0,0,0.3);
    --hover-shadow: rgba(0,0,0,0.4);
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Arial', sans-serif;
    line-height: 1.8;
    color: var(--text-color);
    background-color: var(--bg-color);
    transition: background-color 0.3s, color 0.3s;
}

/* ==========================================================================
   Layout & Grid Styles
   ========================================================================== */
main {
    max-width: 1200px;
    margin: 2rem auto;
    padding: 0 2rem;
}

section {
    margin-bottom: 4rem;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 3rem;
    opacity: 0;
    transform: translateY(20px);
    animation: fadeInUp 0.6s ease forwards;
}

@keyframes fadeInUp {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Grid layouts */
.project-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 2rem;
}

.skills-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

/* ==========================================================================
   Navigation Styles
   ========================================================================== */
nav {
    background-color: var(--secondary-color);
    padding: 1rem;
    position: fixed;
    width: 100%;
    top: 0;
    z-index: 1000;
    box-shadow: 0 2px 5px var(--shadow-color);
}

nav ul {
    list-style: none;
    display: flex;
    justify-content: center;
    align-items: center;
}

nav ul li {
    margin: 0 1rem;
    position: relative;
}

nav ul li a {
    color: white;
    text-decoration: none;
    font-weight: bold;
    padding: 0.5rem 1rem;
    border-radius: 4px;
    transition: background-color 0.3s;
}

nav ul li a:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

nav ul li a.active {
    background-color: var(--primary-color);
}

/* Theme toggle and back to top */
.theme-toggle, .back-to-top {
    background-color: var(--secondary-color);
    color: white;
    border: none;
    padding: 0.5rem;
    border-radius: 50%;
    cursor: pointer;
    position: fixed;
    z-index: 1000;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 2px 5px var(--shadow-color);
    transition: transform 0.3s, background-color 0.3s;
}

.theme-toggle {
    top: 1rem;
    right: 1rem;
}

.back-to-top {
    bottom: 2rem;
    right: 2rem;
    opacity: 0;
    visibility: hidden;
    transform: translateY(10px);
}

.back-to-top.visible {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}

.theme-toggle:hover, .back-to-top:hover {
    background-color: var(--primary-color);
    transform: scale(1.1);
}

/* ==========================================================================
   Header Styles
   ========================================================================== */
header {
    background-color: var(--primary-color);
    color: white;
    text-align: center;
    padding: 8rem 2rem 4rem;
    position: relative;
    overflow: hidden;
}

header::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(45deg, rgba(52, 152, 219, 0.8), rgba(44, 62, 80, 0.8));
    z-index: 1;
}

header > * {
    position: relative;
    z-index: 2;
}

/* ==========================================================================
   Component Styles
   ========================================================================== */
/* Cards */
.project-card, .skill-category {
    background-color: var(--card-bg);
    border: 1px solid var(--border-color);
    padding: 1.5rem;
    border-radius: 8px;
    box-shadow: 0 2px 5px var(--shadow-color);
    transition: all 0.3s ease-in-out;
    position: relative;
    overflow: hidden;
}

.project-card h3, .skill-category h3 {
    font-size: 1.2rem;
    color: var(--text-color);
    margin-bottom: 0.75rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

.project-card p, .skill-category li {
    font-size: 1.1rem;
    line-height: 1.6;
    color: var(--text-color);
    margin-bottom: 1rem;
}

.project-card strong {
    color: var(--primary-color);
    font-size: 1.05rem;
}

.project-card:hover, .skill-category:hover {
    transform: translateY(-8px) scale(1.02);
    box-shadow: 0 8px 15px var(--hover-shadow);
}

.project-card a, .skill-category a {
    text-decoration: none;
    color: inherit;
}

.project-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: linear-gradient(45deg, transparent, rgba(255,255,255,0.1), transparent);
    transform: translateX(-100%);
    transition: transform 0.6s;
}

.project-card:hover::before {
    transform: translateX(100%);
}

/* Project filters */
.project-filters {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 2rem;
    padding: 1rem;
    background-color: var(--card-bg);
    border-radius: 8px;
    box-shadow: 0 2px 5px var(--shadow-color);
}

.filter-btn {
    padding: 0.5rem 1rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: var(--bg-color);
    color: var(--text-color);
    cursor: pointer;
    transition: all 0.3s;
}

.filter-btn:hover, .filter-btn.active {
    background-color: var(--primary-color);
    color: white;
    border-color: var(--primary-color);
}

/* Skill level indicators */
.skill-level {
    height: 6px;
    background-color: var(--border-color);
    border-radius: 3px;
    margin-top: 0.5rem;
    overflow: hidden;
}

.skill-level-fill {
    height: 100%;
    background-color: var(--primary-color);
    border-radius: 3px;
    transition: width 1s ease-in-out;
}

/* Contact form */
.contact-form {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 8px;
    box-shadow: 0 2px 5px var(--shadow-color);
    max-width: 600px;
    margin: 0 auto;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 4px;
    background-color: var(--bg-color);
    color: var(--text-color);
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group textarea:focus {
    border-color: var(--primary-color);
    outline: none;
}

.submit-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: 4px;
    cursor: pointer;
    transition: background-color 0.3s;
}

.submit-btn:hover {
    background-color: var(--secondary-color);
}

/* Social media icons */
.social-links {
    display: flex;
    gap: 1rem;
    margin-top: 1.5rem;
    justify-content: center;
}

.social-icon {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background-color: var(--secondary-color);
    color: white;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    transition: transform 0.3s, background-color 0.3s;
}

.social-icon:hover {
    background-color: var(--primary-color);
    transform: translateY(-3px);
}

/* Loading animation */
@keyframes cardLoading {
    0% {
        opacity: 0;
        transform: translateY(20px);
    }
    100% {
        opacity: 1;
        transform: translateY(0);
    }
}

.project-card {
    animation: cardLoading 0.6s ease forwards;
}

/* Responsive design */
@media (max-width: 768px) {
    nav ul {
        flex-direction: column;
        gap: 1rem;
    }

    .project-grid,
    .skills-container {
        grid-template-columns: 1fr;
    }

    .project-filters {
        flex-direction: column;
    }

    .filter-btn {
        width: 100%;
    }
}

/* ==========================================================================
   Footer Styles
   ========================================================================== */
footer {
    background-color: var(--secondary-color);
    color: white;
    text-align: center;
    padding: 2rem;
    margin-top: 3rem;
}