:root {
    --primary-green: #0f9d58;
    --light-green: #34d399;
    --dark-green: #047857;
    --text-dark: #0f172a;
    --text-light: #64748b;
    --background: #f8fafc;
    --white: #ffffff;
    --border: #e2e8f0;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1);
    
    /* Dark mode variables */
    --dark-bg: #0f172a;
    --dark-card: #1e293b;
    --dark-text: #f1f5f9;
    --dark-text-light: #cbd5e1;
    --dark-border: #334155;
    --dark-shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
}

/* Dark mode styles */
body.dark-mode {
    background: linear-gradient(135deg, #0a5c36 0%, #1a7a52 100%);
    color: var(--dark-text);
}

body.dark-mode .section {
    background: var(--dark-card);
    color: var(--dark-text);
    box-shadow: var(--dark-shadow);
}

body.dark-mode .section h2 {
    color: var(--light-green);
    border-bottom-color: var(--light-green);
}

/* Header Dark Mode */
body.dark-mode .header {
    color: var(--dark-text);
}

/* Modality Grid Dark Mode */
body.dark-mode .modality-btn {
    background: var(--dark-card);
    border-color: var(--dark-border);
    color: var(--dark-text);
}

body.dark-mode .modality-btn:hover {
    background: #1a3a2e;
    border-color: var(--light-green);
}

body.dark-mode .modality-btn.active {
    background: #1a3a2e;
    border-color: var(--light-green);
    color: var(--light-green);
}

body.dark-mode .modality-details {
    color: var(--dark-text-light);
}

/* Configuration Dark Mode */
body.dark-mode .config-group {
    background: var(--dark-card);
    border-color: var(--dark-border);
}

body.dark-mode .config-item label {
    color: var(--dark-text);
}

body.dark-mode .input-group input {
    background: var(--dark-bg);
    border-color: var(--dark-border);
    color: var(--dark-text);
}

body.dark-mode .input-group input:focus {
    border-color: var(--light-green);
    box-shadow: 0 0 0 3px rgba(52, 211, 153, 0.2);
}

body.dark-mode .input-group .unit {
    color: var(--dark-text-light);
}

/* Buttons Dark Mode */
body.dark-mode .btn-secondary {
    background: var(--dark-card);
    color: var(--dark-text);
    border-color: var(--dark-border);
}

body.dark-mode .btn-secondary:hover {
    background: var(--dark-border);
}

/* Storage Cards Dark Mode */
body.dark-mode .storage-card {
    background: var(--dark-card);
    border-color: var(--dark-border);
}

body.dark-mode .storage-card h3 {
    color: var(--light-green);
}

body.dark-mode .storage-item {
    border-bottom-color: var(--dark-border);
}

body.dark-mode .storage-item .label {
    color: var(--dark-text-light);
}

body.dark-mode .storage-item .value {
    color: var(--light-green);
}

/* Savings Card Dark Mode */
body.dark-mode .savings-card {
    background: linear-gradient(135deg, #1a3a2e, #1e4e3e);
    border-color: var(--light-green);
}

body.dark-mode .savings-label {
    color: var(--light-green);
}

body.dark-mode .savings-value {
    color: var(--light-green);
}

/* Total Card Dark Mode */
body.dark-mode .total-card {
    background: var(--dark-card);
    border-color: var(--light-green);
}

body.dark-mode .total-card h3 {
    color: var(--dark-text);
}

body.dark-mode .total-value {
    color: var(--light-green);
}

/* Projection Dark Mode */
body.dark-mode .projection-year {
    background: var(--dark-card);
    border-color: var(--dark-border);
    color: var(--dark-text);
}

body.dark-mode .projection-year.active {
    background: #1a3a2e;
    border-color: var(--light-green);
}

body.dark-mode .year-label {
    color: var(--dark-text-light);
}

body.dark-mode .year-value {
    color: var(--light-green);
}

/* About Section Dark Mode */
body.dark-mode .about-section {
    background: linear-gradient(135deg, var(--dark-card) 0%, #1a3a2e 100%);
}

body.dark-mode .about-text h2 {
    color: var(--light-green);
}

body.dark-mode .lead {
    color: var(--dark-text-light);
}

body.dark-mode .feature-content h4 {
    color: var(--light-green);
}

body.dark-mode .feature-content p {
    color: var(--dark-text-light);
}

body.dark-mode .stat-card {
    background: var(--dark-bg);
    border-color: var(--dark-border);
}

body.dark-mode .stat-number {
    color: var(--light-green);
}

body.dark-mode .stat-label {
    color: var(--dark-text-light);
}

/* Footer Dark Mode */
body.dark-mode .footer {
    background: var(--dark-card);
    box-shadow: var(--dark-shadow);
}

body.dark-mode .footer-section h4 {
    color: var(--light-green);
}

body.dark-mode .footer-section ul li a {
    color: var(--dark-text-light);
}

body.dark-mode .footer-section ul li a:hover {
    color: var(--light-green);
}

body.dark-mode .social-link {
    background: var(--dark-bg);
    color: var(--dark-text-light);
}

body.dark-mode .social-link:hover {
    background: var(--light-green);
    color: var(--dark-bg);
}

body.dark-mode .footer-bottom {
    border-top-color: var(--dark-border);
    color: var(--dark-text-light);
}

/* Theme Toggle Button */
.theme-toggle {
    position: absolute;
    top: 20px;
    right: 20px;
    background: rgba(255, 255, 255, 0.2);
    border: 2px solid rgba(255, 255, 255, 0.3);
    color: white;
    padding: 10px 15px;
    border-radius: 25px;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
    backdrop-filter: blur(10px);
}

.theme-toggle:hover {
    background: rgba(255, 255, 255, 0.3);
    transform: translateY(-2px);
}

body.dark-mode .theme-toggle {
    background: rgba(30, 41, 59, 0.8);
    border-color: rgba(148, 163, 184, 0.3);
    color: var(--dark-text);
}

body.dark-mode .theme-toggle:hover {
    background: rgba(30, 41, 59, 0.9);
}

.theme-text {
    font-weight: 500;
}

/* Header positioning for theme toggle */
.header {
    position: relative;
    text-align: center;
    margin-bottom: 10px;
    color: var(--white);
    padding: 15px 0;
}

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

/* Rest of your existing CSS remains the same */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background: linear-gradient(135deg, var(--primary-green) 0%, var(--light-green) 100%);
    min-height: 100vh;
    transition: background 0.3s ease, color 0.3s ease;
}

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

/* Header Styles */
.header-content h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    font-weight: 700;
    text-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.header-content p {
    font-size: 1.2rem;
    opacity: 0.9;
}

/* Section Styles */
.section {
    background: var(--white);
    border-radius: 20px;
    padding: 30px;
    margin-bottom: 30px;
    box-shadow: var(--shadow);
    transition: transform 0.3s ease, background 0.3s ease, color 0.3s ease;
}

.section:hover {
    transform: translateY(-2px);
}

.section h2 {
    color: var(--dark-green);
    margin-bottom: 25px;
    font-size: 1.5rem;
    border-bottom: 3px solid var(--light-green);
    padding-bottom: 10px;
    transition: color 0.3s ease;
}

/* Modality Grid */
.modality-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 15px;
}

.modality-btn {
    background: var(--background);
    border: 2px solid var(--border);
    border-radius: 12px;
    padding: 20px;
    text-align: left;
    cursor: pointer;
    transition: all 0.3s ease;
    font-weight: 500;
}

.modality-btn:hover {
    background: #f0fdf4;
    border-color: var(--light-green);
    transform: translateY(-2px);
}

.modality-btn.active {
    background: #dcfce7;
    border-color: var(--dark-green);
    color: var(--dark-green);
    font-weight: 600;
}

.modality-name {
    display: block;
    font-size: 1rem;
    margin-bottom: 8px;
    font-weight: 600;
}

.modality-details {
    font-size: 0.9rem;
    color: var(--text-light);
}

/* Configuration Grid */
.config-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(350px, 1fr));
    gap: 25px;
    margin-bottom: 25px;
}

.config-group {
    background: var(--background);
    border-radius: 12px;
    padding: 25px;
    border: 2px solid var(--border);
    transition: all 0.3s ease;
}

.config-item {
    margin-bottom: 20px;
}

.config-item:last-child {
    margin-bottom: 0;
}

.config-item label {
    display: block;
    font-weight: 600;
    color: var(--text-dark);
    margin-bottom: 8px;
    font-size: 0.95rem;
    transition: color 0.3s ease;
}

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

.input-group input {
    flex: 1;
    padding: 12px 15px;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    background: var(--white);
    transition: all 0.3s ease;
}

.input-group input:focus {
    outline: none;
    border-color: var(--dark-green);
    box-shadow: 0 0 0 3px rgba(4, 120, 87, 0.1);
    background: var(--white);
}

.input-group .unit {
    color: var(--text-light);
    font-size: 0.9rem;
    font-weight: 500;
    min-width: 60px;
    text-align: left;
}

/* Reset Section */
.reset-section {
    text-align: center;
    padding-top: 20px;
    border-top: 2px solid var(--border);
}

.btn {
    padding: 12px 30px;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

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

.btn-secondary:hover {
    background: var(--border);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
}

/* Results Grid */
.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
    gap: 25px;
    margin-bottom: 25px;
}

.storage-card {
    background: var(--background);
    border-radius: 12px;
    padding: 25px;
    border: 2px solid var(--border);
    transition: all 0.3s ease;
}

.storage-card h3 {
    color: var(--dark-green);
    margin-bottom: 20px;
    text-align: center;
    font-size: 1.2rem;
    transition: color 0.3s ease;
}

.storage-values {
    display: flex;
    flex-direction: column;
    gap: 15px;
}

.storage-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 0;
    border-bottom: 1px solid var(--border);
    transition: border-color 0.3s ease;
}

.storage-item:last-child {
    border-bottom: none;
}

.storage-item .label {
    color: var(--text-light);
    font-weight: 500;
    transition: color 0.3s ease;
}

.storage-item .value {
    color: var(--dark-green);
    font-weight: 700;
    font-size: 1.1rem;
    transition: color 0.3s ease;
}

/* Savings Card */
.savings-card {
    background: linear-gradient(135deg, #dcfce7, #bbf7d0);
    border-radius: 15px;
    padding: 25px;
    margin-bottom: 25px;
    border: 2px solid #86efac;
    transition: all 0.3s ease;
}

.savings-content {
    display: flex;
    align-items: center;
    gap: 20px;
}

.savings-icon {
    background: var(--dark-green);
    color: white;
    width: 60px;
    height: 60px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
}

.savings-text {
    flex: 1;
}

.savings-label {
    color: var(--dark-green);
    font-weight: 600;
    margin-bottom: 5px;
    font-size: 1.1rem;
}

.savings-value {
    color: var(--dark-green);
    font-size: 2rem;
    font-weight: 700;
}

/* Total Card */
.total-card {
    background: var(--white);
    border-radius: 15px;
    padding: 30px;
    text-align: center;
    margin-bottom: 25px;
    border: 2px dashed var(--light-green);
    transition: all 0.3s ease;
}

.total-card h3 {
    color: var(--text-dark);
    margin-bottom: 15px;
    font-size: 1.3rem;
    transition: color 0.3s ease;
}

.total-value {
    color: var(--dark-green);
    font-size: 2.5rem;
    font-weight: 700;
    transition: color 0.3s ease;
}

/* Projection Section */
.projection-section h3 {
    color: var(--text-dark);
    margin-bottom: 20px;
    text-align: center;
    font-size: 1.3rem;
    transition: color 0.3s ease;
}

.projection-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
    gap: 15px;
}

.projection-year {
    background: var(--background);
    border-radius: 10px;
    padding: 20px;
    text-align: center;
    border: 2px solid var(--border);
    transition: all 0.3s ease;
}

.projection-year.active {
    background: #dcfce7;
    border-color: var(--dark-green);
    transform: scale(1.05);
}

.year-label {
    display: block;
    color: var(--text-light);
    font-weight: 600;
    margin-bottom: 8px;
    font-size: 0.9rem;
    transition: color 0.3s ease;
}

.year-value {
    display: block;
    color: var(--dark-green);
    font-weight: 700;
    font-size: 1.1rem;
    transition: color 0.3s ease;
}

/* About Section */
.about-section {
    background: linear-gradient(135deg, var(--white) 0%, #f0fdf4 100%);
    transition: all 0.3s ease;
}

.about-content {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 40px;
    align-items: start;
}

.about-text h2 {
    color: var(--dark-green);
    font-size: 2rem;
    margin-bottom: 20px;
    border: none;
    transition: color 0.3s ease;
}

.lead {
    font-size: 1.2rem;
    color: var(--text-light);
    margin-bottom: 30px;
    line-height: 1.8;
    transition: color 0.3s ease;
}

.features-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 25px;
    margin-top: 30px;
}

.feature {
    display: flex;
    gap: 15px;
    align-items: flex-start;
}

.feature-icon {
    background: var(--light-green);
    color: white;
    width: 50px;
    height: 50px;
    border-radius: 12px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    flex-shrink: 0;
}

.feature-content h4 {
    color: var(--dark-green);
    margin-bottom: 8px;
    font-size: 1.1rem;
    transition: color 0.3s ease;
}

.feature-content p {
    color: var(--text-light);
    line-height: 1.6;
    transition: color 0.3s ease;
}

.about-stats {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.stat-card {
    background: var(--white);
    border-radius: 15px;
    padding: 25px;
    text-align: center;
    box-shadow: var(--shadow);
    border: 2px solid var(--border);
    transition: all 0.3s ease;
}

.stat-number {
    color: var(--dark-green);
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 8px;
    transition: color 0.3s ease;
}

.stat-label {
    color: var(--text-light);
    font-weight: 500;
    transition: color 0.3s ease;
}

/* Footer */
.footer {
    background: var(--white);
    border-radius: 20px;
    padding: 40px;
    margin-top: 40px;
    box-shadow: var(--shadow);
    transition: all 0.3s ease;
}

.footer-content {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 30px;
    margin-bottom: 30px;
}

.footer-section h4 {
    color: var(--dark-green);
    margin-bottom: 20px;
    font-size: 1.1rem;
    transition: color 0.3s ease;
}

.footer-section ul {
    list-style: none;
}

.footer-section ul li {
    margin-bottom: 12px;
}

.footer-section ul li a {
    color: var(--text-light);
    text-decoration: none;
    transition: color 0.3s ease;
    display: flex;
    align-items: center;
    gap: 8px;
}

.footer-section ul li a:hover {
    color: var(--dark-green);
}

.social-links {
    display: flex;
    gap: 15px;
}

.social-link {
    display: flex;
    align-items: center;
    justify-content: center;
    width: 40px;
    height: 40px;
    background: var(--background);
    color: var(--text-light);
    border-radius: 50%;
    text-decoration: none;
    transition: all 0.3s ease;
}

.social-link:hover {
    background: var(--dark-green);
    color: white;
    transform: translateY(-2px);
}

.footer-bottom {
    text-align: center;
    padding-top: 20px;
    border-top: 1px solid var(--border);
    color: var(--text-light);
    transition: all 0.3s ease;
}

/* Responsive Design */
@media (max-width: 768px) {
    .container {
        padding: 15px;
    }
    
    .header-content h1 {
        font-size: 2rem;
    }
    
    .section {
        padding: 20px;
    }
    
    .config-grid {
        grid-template-columns: 1fr;
    }
    
    .config-group {
        padding: 20px;
    }
    
    .input-group {
        flex-direction: column;
        align-items: stretch;
        gap: 8px;
    }
    
    .input-group .unit {
        text-align: center;
        min-width: auto;
    }
    
    .about-content {
        grid-template-columns: 1fr;
    }
    
    .results-grid {
        grid-template-columns: 1fr;
    }
    
    .projection-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .savings-content {
        flex-direction: column;
        text-align: center;
    }
    
    .theme-toggle {
        position: relative;
        top: auto;
        right: auto;
        margin: 10px auto;
        display: flex;
        justify-content: center;
    }
    
    .header {
        padding-bottom: 60px;
    }
}

/* Animation for results */
@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.fade-in {
    animation: fadeInUp 0.5s ease-out;
}