:root {
    --bg-color: #f8f9fa;
    --text-color: #333;
    --hover-color: #f0f0f0;
    --shadow: 0 2px 8px rgba(0,0,0,0.1);
    --primary-color: #4361ee;
    --primary-dark: #3a56d4;
    --secondary-color: #7209b7;
    --text-light: #6c757d;
    --bg-light: #f8f9fa;
    --bg-dark: #212529;
    --border-color: #dee2e6;
    --success-color: #28a745;
    --error-color: #dc3545;
    --border-radius: 8px;
}

[data-theme="dark"] {
    --bg-color: #1a1a1a;
    --text-color: #f0f0f0;
    --hover-color: #3a3a3a;
    --shadow: 0 2px 8px rgba(0,0,0,0.3);
    --primary-color: #5a75f0;
    --primary-dark: #4d67d8;
    --secondary-color: #8a2be2;
    --text-light: #adb5bd;
    --bg-light: #1e1e1e;
    --bg-dark: #0a0a0a;
    --border-color: #343a40;
}

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

body {
    font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
    line-height: 1.6;
    color: var(--text-color);
    background-color: var(--bg-color);
    transition: background-color 0.3s ease, color 0.3s ease;
    min-height: 100vh;
}

.container {
    width: 100%;
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Theme Toggle */
.theme-toggle {
    position: absolute;
    top: 4.5rem;
    right: 1.5rem;
    background: none;
    border: none;
    color: var(--text-color);
    cursor: pointer;
    font-size: 1.5rem;
    padding: 0.5rem;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 3rem;
    height: 3rem;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
    z-index: 100;
}

.theme-toggle:hover {
    background-color: var(--hover-color);
    transform: scale(1.1);
}

/* Hero Section */
.hero {
    padding: 60px 0 40px;
    text-align: center;
    background-color: var(--bg-light);
    position: relative;
}

.hero h1 {
    font-size: 2.5rem;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.hero p {
    font-size: 1.2rem;
    max-width: 700px;
    margin: 0 auto;
    color: var(--text-light);
}

/* Tool Section */
.tool-section {
    padding: 40px 0;
}

.tool-container {
    background-color: var(--bg-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    padding: 30px;
    margin-bottom: 30px;
}

.upload-area {
    border: 2px dashed var(--border-color);
    border-radius: var(--border-radius);
    padding: 40px 20px;
    text-align: center;
    margin-bottom: 30px;
    transition: all 0.3s ease;
    cursor: pointer;
    position: relative;
}

.upload-area:hover {
    border-color: var(--primary-color);
    background-color: var(--hover-color);
}

.upload-area i {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.upload-area h3 {
    margin-bottom: 10px;
}

.upload-area p {
    color: var(--text-light);
    margin-bottom: 20px;
}

.btn {
    display: inline-block;
    color: white;
    padding: 12px 24px;
    border-radius: var(--border-radius);
    border: none;
    cursor: pointer;
    font-size: 1rem;
    font-weight: 600;
    transition: all 0.3s ease;
    text-decoration: none;
}

.btn-split {
    background: linear-gradient(135deg, #4361ee, #4cc9f0);
    box-shadow: 0 4px 15px rgba(67, 97, 238, 0.3);
}

.btn-split:hover {
    background: linear-gradient(135deg, #3a56d4, #3ab9e0);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(67, 97, 238, 0.4);
}

.btn-download-all {
    background: linear-gradient(135deg, #28a745, #20c997);
    box-shadow: 0 4px 15px rgba(40, 167, 69, 0.3);
}

.btn-download-all:hover {
    background: linear-gradient(135deg, #218838, #1ba87e);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(40, 167, 69, 0.4);
}

.btn-download-single {
    background: linear-gradient(135deg, #28a745, #20c997);
    box-shadow: 0 2px 8px rgba(40, 167, 69, 0.3);
    padding: 6px 12px;
    font-size: 0.8rem;
    margin-left: 8px;
}

.btn-download-single:hover {
    background: linear-gradient(135deg, #218838, #1ba87e);
    transform: translateY(-1px);
}

.btn-download-option {
    background: linear-gradient(135deg, #28a745, #20c997);
    box-shadow: 0 4px 15px rgba(40, 167, 69, 0.3);
    margin: 5px;
}

.btn-download-option:hover {
    background: linear-gradient(135deg, #218838, #1ba87e);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(40, 167, 69, 0.4);
}

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

.btn-secondary:hover {
    background-color: #5e0a9c;
}

.btn-outline {
    background-color: transparent;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
}

.btn-outline:hover {
    background-color: var(--primary-color);
    color: white;
}

.range-selector {
    margin: 30px 0;
}

.range-selector h3 {
    margin-bottom: 15px;
}

.range-inputs {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
    align-items: center;
}

.range-input {
    display: flex;
    align-items: center;
    gap: 10px;
}

.range-input input {
    padding: 10px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    width: 80px;
    background-color: var(--bg-color);
    color: var(--text-color);
}

.range-display {
    margin-top: 20px;
    padding: 15px;
    background-color: var(--bg-light);
    border-radius: var(--border-radius);
}

.range-display h4 {
    margin-bottom: 10px;
}

.range-list {
    display: flex;
    flex-wrap: wrap;
    gap: 10px;
}

.range-item {
    background-color: var(--primary-color);
    color: white;
    padding: 5px 10px;
    border-radius: 20px;
    font-size: 0.9rem;
    display: flex;
    align-items: center;
}

.range-item.split-completed {
    background-color: transparent;
    border: 1px solid var(--primary-color);
    color: var(--primary-color);
}

.action-buttons {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
    margin-top: 20px;
}

.download-options {
    display: flex;
    gap: 15px;
    flex-wrap: wrap;
    margin-top: 15px;
    justify-content: center;
}

.hidden {
    display: none;
}

.processing {
    position: relative;
    pointer-events: none;
}

.processing::after {
    content: "";
    position: absolute;
    top: 50%;
    left: 50%;
    margin: -10px 0 0 -10px;
    width: 20px;
    height: 20px;
    border: 2px solid transparent;
    border-top: 2px solid white;
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

/* Features Section */
.features-section {
    padding: 40px 0;
    background-color: var(--bg-light);
}

.section-title {
    text-align: center;
    margin-bottom: 30px;
}

.section-title h2 {
    font-size: 2rem;
    color: var(--primary-color);
    margin-bottom: 10px;
}

.section-title p {
    color: var(--text-light);
    max-width: 600px;
    margin: 0 auto;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
}

.feature-card {
    background-color: var(--bg-color);
    border-radius: var(--border-radius);
    padding: 25px;
    text-align: center;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.feature-card:hover {
    transform: translateY(-5px);
}

.feature-icon {
    font-size: 2.5rem;
    color: var(--primary-color);
    margin-bottom: 15px;
}

.feature-card h3 {
    margin-bottom: 10px;
}

.feature-card p {
    color: var(--text-light);
}

/* FAQ Section */
.faq-section {
    padding: 40px 0;
}

.faq-container {
    max-width: 800px;
    margin: 0 auto;
}

.faq-item {
    margin-bottom: 15px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    overflow: hidden;
}

.faq-question {
    padding: 20px;
    background-color: var(--bg-color);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-weight: 600;
    transition: all 0.3s ease;
}

.faq-question:hover {
    background-color: var(--bg-light);
}

.faq-question i {
    transition: all 0.3s ease;
}

.faq-answer {
    padding: 0 20px;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, padding 0.3s ease;
    background-color: var(--bg-light);
}

.faq-item.active .faq-answer {
    padding: 20px;
    max-height: 2000px; /* Increased to ensure all content is visible */
}

.faq-item.active .faq-question i {
    transform: rotate(180deg);
}

/* About Section */
.about-section {
    padding: 40px 0;
    background-color: var(--bg-light);
}

.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.about-content h2 {
    font-size: 2rem;
    margin-bottom: 20px;
    color: var(--primary-color);
}

.about-content p {
    margin-bottom: 20px;
    color: var(--text-color);
}

/* Responsive Design */
@media (max-width: 768px) {
    .hero h1 {
        font-size: 2rem;
    }
    
    .hero p {
        font-size: 1rem;
    }
    
    .tool-container {
        padding: 20px;
    }
    
    .range-inputs {
        flex-direction: column;
        align-items: flex-start;
    }
    
    .action-buttons {
        flex-direction: column;
    }
    
    .btn {
        width: 100%;
        text-align: center;
    }
    
    .theme-toggle {
        top: 3.5rem;
        right: 1rem;
        width: 2.5rem;
        height: 2.5rem;
        font-size: 1.2rem;
    }
}