/* CSS Custom Properties */
:root {
    /* Eco-friendly color palette */
    --primary: #10b981;
    --secondary: #059669;
    --accent: #34d399;
    --danger: #ef4444;
    --warning: #f59e0b;
    --info: #3b82f6;
    --text: #1f2937;
    --text-light: #6b7280;
    --bg: #f3f4f6;
    --white: #ffffff;
    
    /* Spacing scale */
    --spacing-xs: 0.5rem;
    --spacing-sm: 1rem;
    --spacing-md: 1.5rem;
    --spacing-lg: 2rem;
    --spacing-xl: 3rem;
    
    /* Border radius */
    --radius: 0.5rem;
    --radius-lg: 1rem;
    
    /* Shadows */
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
}

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

body {
    min-height: 100vh;
    background: linear-gradient(135deg, #d4fc79 0%, #96e6a1 100%);
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    color: var(--text);
    line-height: 1.6;
}

.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--spacing-md);
}

/* Utility Classes */
.hidden {
    display: none !important;
}

.section-title {
    font-size: 1.875rem;
    font-weight: 700;
    color: var(--text);
    margin-bottom: var(--spacing-md);
}

/* Header Styles */
.header {
    background-color: var(--white);
    box-shadow: var(--shadow-md);
    padding: var(--spacing-lg) var(--spacing-md);
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

.header__title {
    color: var(--primary);
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: var(--spacing-sm);
}

.header__subtitle {
    color: var(--text-light);
    font-size: 1rem;
    max-width: 600px;
    margin: 0 auto;
}

/* Main Content */
.main {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 var(--spacing-md);
}

/* Form Styles */
.calculator-form {
    background-color: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.form-group {
    margin-bottom: var(--spacing-md);
}

.form-group__label {
    display: block;
    font-weight: 600;
    margin-bottom: var(--spacing-xs);
    color: var(--text);
}

.form-group__input {
    width: 100%;
    padding: var(--spacing-sm);
    border: 2px solid var(--bg);
    border-radius: var(--radius);
    font-size: 1rem;
    transition: all 0.3s ease;
}

.form-group__input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.1);
}

.form-group__input:read-only {
    background-color: var(--bg);
    cursor: not-allowed;
}

.form-group__helper-text {
    display: block;
    font-size: 0.875rem;
    color: var(--text-light);
    margin-top: var(--spacing-xs);
}

.form-group__checkbox {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    cursor: pointer;
    margin-top: var(--spacing-sm);
}

.form-group__checkbox-input {
    width: 1.25rem;
    height: 1.25rem;
    cursor: pointer;
}

.form-group__checkbox-label {
    font-weight: 500;
    color: var(--text);
}

/* Transport Mode Grid */
.transport-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-sm);
    margin-top: var(--spacing-sm);
}

.transport-grid__option {
    position: relative;
    cursor: pointer;
}

.transport-grid__radio {
    position: absolute;
    opacity: 0;
    width: 0;
    height: 0;
}

.transport-grid__label {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: var(--spacing-md);
    border: 2px solid var(--bg);
    border-radius: var(--radius);
    background-color: var(--white);
    transition: all 0.3s ease;
    min-height: 120px;
}

.transport-grid__label:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.transport-grid__icon {
    font-size: 3rem;
    margin-bottom: var(--spacing-xs);
}

.transport-grid__text {
    font-weight: 600;
    color: var(--text);
    text-align: center;
}

.transport-grid__radio:checked + .transport-grid__label {
    border-color: var(--primary);
    border-width: 2px;
    background-color: rgba(16, 185, 129, 0.05);
}

/* Submit Button */
.form-submit {
    width: 100%;
    padding: var(--spacing-md);
    background-color: var(--primary);
    color: var(--white);
    font-size: 1rem;
    font-weight: 600;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.3s ease;
    margin-top: var(--spacing-sm);
}

.form-submit:hover {
    background-color: var(--secondary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.form-submit:disabled {
    background-color: var(--text-light);
    cursor: not-allowed;
    transform: none;
}

/* Results Sections */
.results,
.comparison,
.carbon-credits {
    background-color: var(--white);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
    animation: fadeIn 0.5s ease-out;
}

.results__content,
.comparison__content,
.carbon-credits__content {
    color: var(--text);
}

/* Results Grid */
.results__grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.results__card {
    background-color: var(--white);
    padding: 1.5rem;
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--bg);
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    transition: all 0.3s ease;
}

.results__card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.results__card--highlight {
    border: 2px solid var(--primary);
    background-color: rgba(16, 185, 129, 0.05);
}

.results__card--success {
    border: 2px solid var(--accent);
    background-color: rgba(52, 211, 153, 0.05);
}

.results__card-icon {
    font-size: 2.5rem;
    flex-shrink: 0;
}

.results__card-content {
    flex: 1;
}

.results__card-title {
    font-size: 0.875rem;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
    font-weight: 600;
}

.results__card-value {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text);
    line-height: 1.2;
}

.results__card-value--large {
    font-size: 2rem;
    color: var(--primary);
}

.results__card-subtitle {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-top: 0.25rem;
}

/* Comparison Section */
.comparison__grid {
    display: grid;
    gap: var(--spacing-md);
    margin-top: var(--spacing-md);
}

.comparison__item {
    background-color: var(--white);
    padding: 1.5rem;
    border: 2px solid var(--bg);
    border-radius: var(--radius);
    transition: all 0.3s ease;
}

.comparison__item:hover {
    border-color: var(--accent);
    box-shadow: var(--shadow-md);
}

.comparison__item--selected {
    border-color: var(--primary);
    background-color: rgba(16, 185, 129, 0.05);
    box-shadow: var(--shadow-md);
}

.comparison__header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--spacing-sm);
}

.comparison__icon {
    font-size: 1.5rem;
    margin-right: 0.5rem;
}

.comparison__label {
    font-weight: 700;
    color: var(--text);
    font-size: 1.125rem;
}

.comparison__badge {
    background-color: var(--primary);
    color: var(--white);
    padding: 0.25rem 0.75rem;
    border-radius: 9999px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.comparison__stats {
    display: flex;
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-sm);
}

.comparison__stat {
    display: flex;
    flex-direction: column;
}

.comparison__stat-label {
    font-size: 0.75rem;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 0.25rem;
}

.comparison__stat-value {
    font-size: 1.125rem;
    font-weight: 700;
    color: var(--text);
}

.comparison__bar-container {
    width: 100%;
    height: 12px;
    background-color: var(--bg);
    border-radius: 9999px;
    overflow: hidden;
    margin-top: var(--spacing-sm);
}

.comparison__bar {
    height: 100%;
    border-radius: 9999px;
    transition: width 0.5s ease;
}

.comparison__tip {
    background-color: rgba(59, 130, 246, 0.1);
    border-left: 4px solid var(--info);
    padding: var(--spacing-md);
    border-radius: var(--radius);
    margin-top: var(--spacing-lg);
    display: flex;
    gap: var(--spacing-sm);
    align-items: flex-start;
}

.comparison__tip-icon {
    font-size: 1.5rem;
    flex-shrink: 0;
}

.comparison__tip-text {
    flex: 1;
    line-height: 1.6;
    color: var(--text);
}

.comparison__tip-text strong {
    color: var(--info);
}

/* Carbon Credits Section */
.carbon-credits__grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: var(--spacing-lg);
    margin-bottom: var(--spacing-lg);
}

.carbon-credits__card {
    background-color: var(--white);
    padding: var(--spacing-lg);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--bg);
    transition: all 0.3s ease;
}

.carbon-credits__card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.carbon-credits__card-header {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.carbon-credits__icon {
    font-size: 2rem;
}

.carbon-credits__card-title {
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-light);
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.carbon-credits__card-body {
    text-align: center;
}

.carbon-credits__value {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--primary);
    line-height: 1;
    margin-bottom: 0.5rem;
}

.carbon-credits__helper {
    font-size: 0.875rem;
    color: var(--text-light);
    margin-top: var(--spacing-xs);
}

.carbon-credits__info {
    background-color: rgba(59, 130, 246, 0.05);
    border: 2px dashed var(--info);
    padding: var(--spacing-md);
    border-radius: var(--radius);
    margin-bottom: var(--spacing-lg);
}

.carbon-credits__info-title {
    font-weight: 700;
    color: var(--info);
    margin-bottom: var(--spacing-xs);
    font-size: 1rem;
}

.carbon-credits__info-text {
    line-height: 1.6;
    color: var(--text);
    font-size: 0.9375rem;
}

.carbon-credits__action {
    text-align: center;
}

.carbon-credits__button {
    width: 100%;
    padding: var(--spacing-md);
    background-color: var(--primary);
    color: var(--white);
    font-size: 1rem;
    font-weight: 700;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.3s ease;
}

.carbon-credits__button:hover {
    background-color: var(--secondary);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.carbon-credits__button:active {
    transform: translateY(0);
}

/* Loading Spinner */
.spinner {
    display: inline-block;
    width: 40px;
    height: 40px;
    border: 4px solid var(--bg);
    border-top-color: var(--primary);
    border-radius: 50%;
    animation: spin 1s linear infinite;
}

@keyframes spin {
    to {
        transform: rotate(360deg);
    }
}

/* Fade In Animation */
@keyframes fadeIn {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* Footer */
.footer {
    background-color: var(--white);
    box-shadow: var(--shadow-md);
    padding: var(--spacing-lg) var(--spacing-md);
    text-align: center;
    margin-top: var(--spacing-xl);
}

.footer__credits {
    color: var(--text-light);
    font-size: 0.875rem;
}

/* Responsive Design */
@media (max-width: 767px) {
    .header__title {
        font-size: 1.5rem;
    }
    
    .header__subtitle {
        font-size: 0.875rem;
    }
    
    .calculator-form {
        padding: var(--spacing-md);
    }
    
    .transport-grid {
        grid-template-columns: repeat(2, 1fr);
    }
    
    .transport-grid__icon {
        font-size: 2.5rem;
    }
    
    /* Results responsive */
    .results__grid {
        grid-template-columns: 1fr;
    }
    
    .results__card-value--large {
        font-size: 1.5rem;
    }
    
    /* Comparison responsive */
    .comparison__stats {
        flex-direction: column;
        gap: var(--spacing-sm);
    }
    
    /* Carbon Credits responsive */
    .carbon-credits__grid {
        grid-template-columns: 1fr;
    }
    
    .carbon-credits__value {
        font-size: 2rem;
    }
    
    .section-title {
        font-size: 1.5rem;
    }
}

@media (min-width: 768px) {
    .header__title {
        font-size: 2.5rem;
    }
    
    .transport-grid {
        grid-template-columns: repeat(4, 1fr);
    }
    
    .calculator-form {
        padding: var(--spacing-xl);
    }
    
    .results__grid {
        grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    }
}