/* A. Theme Variables (Crucial for Dark/Light Mode) */
:root {
    /* Base Colors */
    --color-primary: #007BFF; /* Vibrant Blue */
    --color-primary-hover: #0056b3; 
    --color-text-light: #F0F0F0;
    --color-text-dark: #333333;
    --color-background-dark: #121212;
    --color-background-light: #FFFFFF;
    --color-card-dark: #1E1E1E;
    --color-card-light: #F8F8F8;
    --color-border-dark: #333333;
    --color-border-light: #E0E0E0;

    /* Theme-specific variables (Default: Dark) */
    --color-background: var(--color-background-dark);
    --color-text: var(--color-text-light);
    --color-card: var(--color-card-dark);
    --color-border: var(--color-border-dark);

    --transition-speed: 0.3s;
}

/* Light Mode Override */
html[data-theme="light"] {
    --color-background: var(--color-background-light);
    --color-text: var(--color-text-dark);
    --color-card: var(--color-card-light);
    --color-border: var(--color-border-light);
}

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

body {
    font-family: 'Poppins', sans-serif;
    background-color: var(--color-background);
    color: var(--color-text);
    line-height: 1.6;
    transition: background-color var(--transition-speed), color var(--transition-speed);
}

.container {
    width: 90%;
    max-width: 1200px;
    margin: 0 auto;
}

/* Headings */
h1, h2, h3, h4 {
    font-weight: 700;
    margin-bottom: 0.5em;
}

h2 {
    font-size: 2.5rem;
    color: var(--color-primary);
    text-align: center;
    margin-bottom: 2rem;
    position: relative;
}

h2::after {
    content: '';
    display: block;
    width: 60px;
    height: 3px;
    background: var(--color-primary);
    margin: 10px auto 0;
    border-radius: 5px;
}

.section-padding {
    padding: 80px 0;
}

/* C. Core Component Styles */
/* Navigation */
header {
    position: sticky;
    top: 0;
    z-index: 1000;
    background: var(--color-card);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.1);
}

nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 15px 0;
    position: relative; 
}

.logo {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--color-primary);
}

/* --- Mobile Menu Toggle and Styles --- */
/* Hide the toggle button by default (Desktop view) */
.menu-toggle {
    display: none; 
    background: none;
    border: none;
    color: var(--color-primary);
    cursor: pointer;
    font-size: 1.5rem;
    padding: 5px;
    margin-left: 15px;
    z-index: 1100; 
}

.nav-links {
    list-style: none;
    display: flex; /* Default: Desktop view (horizontal) */
}

/* Mobile Menu Expanded State (Toggled by JS) */
.nav-links.active {
    display: flex;
    flex-direction: column;
    position: absolute;
    top: 100%; 
    left: 0;
    width: 100%;
    background-color: var(--color-card);
    border-top: 1px solid var(--color-border);
    box-shadow: 0 5px 15px rgba(0, 0, 0, 0.1);
    padding: 10px 0;
}

.nav-links.active li {
    text-align: center;
    width: 100%;
    margin: 0;
    padding: 5px 0;
    border-bottom: 1px solid var(--color-border);
}
.nav-links.active li:last-child {
    border-bottom: none;
}
.nav-links.active a {
    display: block;
    margin: 0;
    padding: 10px 20px;
}
/* ------------------------------------------------ */

.nav-links a {
    color: var(--color-text);
    text-decoration: none;
    font-weight: 600;
    margin-left: 25px;
    transition: color var(--transition-speed);
}

.nav-links a:hover {
    color: var(--color-primary);
}

/* Theme Toggle Button */
.theme-toggle {
    background: none;
    border: 2px solid var(--color-primary);
    color: var(--color-primary);
    cursor: pointer;
    padding: 8px 12px;
    border-radius: 8px;
    font-size: 1.1rem;
    transition: background var(--transition-speed);
    margin-left: 15px; /* Separate from nav links */
}

.theme-toggle:hover {
    background: var(--color-primary);
    color: var(--color-background-dark);
}

/* Hero Section */
.hero {
    min-height: 80vh;
    display: flex;
    align-items: center;
    justify-content: space-around;
    padding-top: 100px;
    gap: 40px;
}

.hero-content {
    max-width: 600px;
}

.hero .greeting {
    font-size: 1.1rem;
}

.hero h1 {
    font-size: 4rem;
    color: var(--color-primary);
    margin-bottom: 0.1em;
}

.hero .tagline {
    font-size: 1.5rem;
    font-weight: 400;
    margin-bottom: 1rem;
}

.hero-image img {
    width: 300px;
    height: 300px;
    border-radius: 50%;
    object-fit: cover;
    border: 5px solid var(--color-primary);
    box-shadow: 0 0 20px rgba(0, 123, 255, 0.4);
}

/* Call-to-Action Buttons */
.cta-buttons {
    margin-top: 2rem;
    display: flex;
    gap: 15px;
}

.btn {
    text-decoration: none;
    padding: 12px 25px;
    border-radius: 10px;
    font-weight: 600;
    transition: all var(--transition-speed);
    display: inline-block;
}

.btn-primary {
    background-color: var(--color-primary);
    color: var(--color-background-dark);
    border: 2px solid var(--color-primary);
}

.btn-primary:hover {
    background-color: var(--color-primary-hover);
    transform: translateY(-3px);
    box-shadow: 0 4px 10px rgba(0, 123, 255, 0.3);
}

.btn-secondary {
    background: none;
    color: var(--color-primary);
    border: 2px solid var(--color-primary);
}

.btn-secondary:hover {
    background-color: var(--color-primary);
    color: var(--color-background-dark);
    transform: translateY(-3px);
}

/* Card Base Style */
.card {
    background-color: var(--color-card);
    border: 1px solid var(--color-border);
    border-radius: 12px;
    padding: 20px;
    box-shadow: 0 4px 15px rgba(0, 0, 0, 0.1);
    transition: transform 0.3s ease-in-out, box-shadow 0.3s ease-in-out;
}

.card:hover {
    transform: translateY(-5px);
    box-shadow: 0 8px 25px rgba(0, 123, 255, 0.15);
}

/* --- Skills Section Styles (Revised) --- */
.skills-category-container {
    display: flex;
    gap: 30px;
    flex-wrap: wrap;
    justify-content: center;
}

.skills-column {
    flex: 1;
    min-width: 280px;
    padding: 20px;
    border-radius: 12px;
    border: 1px solid var(--color-border);
    background-color: var(--color-card);
}

.skills-column h3 {
    font-size: 1.4rem;
    color: var(--color-primary);
    border-bottom: 2px solid var(--color-border);
    padding-bottom: 10px;
    margin-bottom: 15px;
    display: flex;
    align-items: center;
}

.skills-column h3 i {
    margin-right: 10px;
}

.skills-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr); /* Two columns for skills in each category */
    gap: 15px;
    text-align: center;
}

.skill-item {
    padding: 10px;
    background-color: var(--color-background);
    border-radius: 8px;
    border: 1px solid var(--color-border);
    transition: background-color 0.3s;
}

.skill-item:hover {
    background-color: var(--color-primary-hover);
    color: var(--color-background-dark);
}
.skill-item:hover i {
    color: var(--color-background-dark);
}

.skill-item i {
    font-size: 2rem;
    color: var(--color-primary);
    margin-bottom: 5px;
    display: block;
}
.skill-item p {
    font-size: 0.9rem;
    font-weight: 600;
}


/* Projects Grid */
.projects-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
}

.project-card img {
    width: 100%;
    height: 200px;
    object-fit: cover;
    border-radius: 8px 8px 0 0;
    margin-bottom: 15px;
}

.project-content {
    padding: 0 10px 10px;
}

.tech-stack span {
    display: inline-block;
    background-color: var(--color-primary);
    color: var(--color-background-dark);
    font-size: 0.75rem;
    padding: 4px 8px;
    border-radius: 5px;
    margin-right: 5px;
    margin-top: 10px;
    font-family: 'Fira Code', monospace;
}

.project-links a {
    margin-right: 15px;
    color: var(--color-primary);
    text-decoration: none;
    font-weight: 600;
}

/* --- Experience & Education Specific Styles --- */
/* Overall container for layout */
#experience .container {
    display: grid;
    grid-template-columns: 2fr 1fr; /* Experience is wider than Education */
    gap: 40px;
}

.experience-group h3, .education-group h3 {
    font-size: 1.8rem;
    color: var(--color-text); 
    border-bottom: 2px solid var(--color-primary);
    padding-bottom: 5px;
    margin-bottom: 20px;
    display: flex;
    align-items: center;
}

.experience-group h3 i, .education-group h3 i {
    color: var(--color-primary);
    margin-right: 10px;
}

.experience-item, .education-item {
    margin-bottom: 20px;
    padding: 15px;
}

.experience-item h4 {
    color: var(--color-primary);
    margin-bottom: 5px;
    font-size: 1.2rem;
    display: block; 
}

.experience-item .date-range {
    display: block;
    font-size: 0.9rem;
    color: var(--color-text);
    opacity: 0.8;
    margin-bottom: 10px;
    font-weight: 600;
}

.experience-item ul {
    list-style: disc;
    padding-left: 20px;
    margin-top: 10px;
}

.experience-item ul li {
    margin-bottom: 5px;
}

/* Education specific styles */
.education-group {
    grid-column: 2 / 3; /* Place in the second column */
}
.education-item h4 {
    font-size: 1.1rem;
}
.education-item p {
    margin-bottom: 10px;
}
.education-item strong {
    color: var(--color-primary);
}

/* --- Certifications Grid Styles --- */
.certifications-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 30px;
    margin-top: 2rem;
}

.certification-item {
    padding: 20px;
}

.certification-item h4 {
    color: var(--color-primary);
    margin-bottom: 10px;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
}

.certification-item h4 i {
    margin-right: 10px;
    font-size: 1.5rem;
}

.certification-item p {
    font-size: 0.95rem;
    line-height: 1.5;
}

/* --- New Achievements Section Styles --- */
.achievements-list {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 30px;
    margin-top: 2rem;
}

.achievement-item {
    padding: 20px;
}

.achievement-item h4 {
    color: var(--color-primary);
    margin-bottom: 10px;
    font-size: 1.2rem;
    display: flex;
    align-items: center;
}

.achievement-item h4 i {
    margin-right: 10px;
    font-size: 1.5rem;
}

.achievement-item p {
    font-size: 0.95rem;
    line-height: 1.5;
}

/* --- Image Gallery Styles (New) --- */
#gallery .container {
    padding-bottom: 0; 
}

.slider-container {
    position: relative;
    width: 100%;
    max-width: 900px; 
    margin: 40px auto;
    overflow: hidden;
    border-radius: 15px;
    box-shadow: 0 8px 25px rgba(0, 0, 0, 0.2);
    border: 1px solid var(--color-border);
}

.slider-track {
    display: flex;
    transition: transform 0.5s ease-in-out;
}

.slider-image {
    width: 100%;
    height: 500px; 
    object-fit: contain; 
    flex-shrink: 0;
    display: block; 
    background-color: var(--color-card); 
    padding: 10px;
}

.slider-nav {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    background-color: rgba(0, 0, 0, 0.5);
    color: white;
    border: none;
    padding: 15px 10px;
    cursor: pointer;
    font-size: 1.5rem;
    border-radius: 5px;
    transition: background-color 0.3s ease;
    z-index: 10;
}

.slider-nav:hover {
    background-color: rgba(0, 0, 0, 0.8);
}

.slider-nav.prev {
    left: 10px;
}

.slider-nav.next {
    right: 10px;
}


/* Contact Form */
.contact-content {
    display: flex;
    gap: 50px;
    align-items: flex-start;
}

.contact-form {
    flex: 1;
}

.contact-info {
    flex: 1;
    padding-top: 20px;
}

.contact-info p {
    margin-bottom: 15px;
}

.contact-info a {
    color: var(--color-primary);
    text-decoration: none;
    margin-left: 10px;
}

form label {
    display: block;
    margin-bottom: 5px;
    font-weight: 600;
}

form input, form textarea {
    width: 100%;
    padding: 10px;
    margin-bottom: 20px;
    border: 1px solid var(--color-border);
    background-color: var(--color-card);
    color: var(--color-text);
    border-radius: 8px;
    transition: border-color var(--transition-speed);
}

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

/* Footer */
footer {
    background-color: var(--color-card);
    padding: 20px 0;
    text-align: center;
    border-top: 1px solid var(--color-border);
}

footer .social-links a {
    color: var(--color-text);
    font-size: 1.5rem;
    margin: 0 10px;
    transition: color var(--transition-speed);
}

footer .social-links a:hover {
    color: var(--color-primary);
}

/* --- Animations & Visibility (for JS Intersection Observer) --- */
.hidden {
    opacity: 0;
    transform: translateY(20px);
    transition: opacity 0.6s ease-out, transform 0.6s ease-out;
}

.visible {
    opacity: 1;
    transform: translateY(0);
}

/* D. Responsiveness */
/* Tablet/Mobile Breakpoint */
@media (max-width: 900px) {
    /* 1. Mobile Navigation Logic */
    .nav-links {
        display: none; /* Hide horizontal menu on mobile */
    }
    .menu-toggle {
        display: block; /* Show hamburger button on mobile */
    }
    
    /* 2. Hero Section */
    .hero {
        flex-direction: column;
        text-align: center;
        padding-top: 80px;
    }

    .hero-image {
        order: -1;
        margin-bottom: 20px;
    }

    .hero h1 {
        font-size: 2.8rem;
    }

    .hero .tagline {
        font-size: 1.2rem;
    }
    
    .cta-buttons {
        justify-content: center;
        flex-direction: column; 
    }
    .btn {
        width: 100%; 
    }

    /* 3. Skills Section */
    .skills-category-container {
        flex-direction: column;
    }
    .skills-column {
        min-width: unset;
    }

    /* 4. Grid Sections (Projects, Certifications, Achievements) */
    .skills-grid, .projects-grid, .certifications-grid, .achievements-list {
        grid-template-columns: 1fr; /* Single column layout */
    }
    
    /* 5. Experience/Education Section */
    #experience .container {
        grid-template-columns: 1fr; /* Stack into a single column on small screens */
        gap: 30px;
    }
    .education-group {
        grid-column: 1 / -1; /* Reset column span to full width */
    }
    
    /* 6. Contact Section */
    .contact-content {
        flex-direction: column;
    }

    /* 7. Gallery/Slider */
    .slider-image {
        height: 300px; 
    }
}

/* Mobile Phone Breakpoint */
@media (max-width: 600px) {
    .section-padding {
        padding: 60px 0;
    }
    h2 {
        font-size: 2rem;
    }
    .hero h1 {
        font-size: 2.2rem;
    }
    .hero-image img {
        width: 200px;
        height: 200px;
    }
    .slider-image {
        height: 250px; 
    }
    /* Reduce padding on the slider nav buttons */
    .slider-nav {
        padding: 10px 5px;
        font-size: 1.2rem;
    }
    .cta-buttons {
        gap: 10px;
    }
}