:root {
    --primary: #3b82f6;
    --primary-dark: #2563eb;
    --primary-light: #60a5fa;
    --primary-bg: rgba(59, 130, 246, 0.1);
    --text: #1f2937;
    --text-light: #6b7280;
    --light-gray: #f3f4f6;
    --medium-gray: #e5e7eb;
    --dark-gray: #4b5563;
    --white: #ffffff;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --radius: 8px;
    --transition: all 0.3s ease;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    line-height: 1.6;
    color: var(--text);
    background-color: #f9fafb;
    padding: 20px;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 0 15px;
}

/* Header */
.header {
    text-align: center;
    margin-bottom: 2.5rem;
    padding: 2rem 0;
}

.logo {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1rem;
}

.logo i {
    font-size: 2.5rem;
    color: var(--primary);
}

h1 {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text);
    margin: 0;
}

.subtitle {
    color: var(--text-light);
    font-size: 1.1rem;
    margin-top: 0.5rem;
}

/* Card */
.card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem;
    margin-bottom: 2rem;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 2rem;
    overflow-x: auto;
    padding-bottom: 0.5rem;
}

.tab-btn {
    background: var(--light-gray);
    border: none;
    padding: 0.75rem 1.25rem;
    border-radius: 50px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    white-space: nowrap;
    font-size: 0.9rem;
}

.tab-btn:hover {
    background: var(--medium-gray);
}

.tab-btn.active {
    background: var(--primary);
    color: var(--white);
}

.tab-content {
    display: none;
}

.tab-content.active {
    display: block;
    animation: fadeIn 0.3s ease;
}

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

label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
    color: var(--text);
}

.date-input {
    width: 100%;
    padding: 0.75rem 1rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--radius);
    font-size: 1rem;
    transition: var(--transition);
}

.date-input:focus {
    outline: none;
    border-color: var(--primary);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.2);
}

/* Buttons */
.calculate-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    background: linear-gradient(135deg, var(--primary), var(--primary-dark));
    color: var(--white);
    border: none;
    padding: 0.875rem 1.75rem;
    border-radius: var(--radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    transition: var(--transition);
    margin-top: 1rem;
}

.calculate-btn:hover {
    background: linear-gradient(135deg, var(--primary-dark), var(--primary));
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.2);
}

.calculate-btn:active {
    transform: translateY(0);
}

/* Results */
.result {
    margin-top: 1.5rem;
    padding: 1.5rem;
    background: var(--primary-bg);
    border-radius: var(--radius);
    text-align: center;
    font-size: 1.1rem;
    line-height: 1.6;
    display: none;
}

.result.show {
    display: block;
    animation: fadeIn 0.3s ease;
}

.result .highlight {
    font-size: 1.4rem;
    font-weight: 700;
    color: var(--primary-dark);
    margin: 0.5rem 0;
    display: block;
}

/* Info Card */
.info-card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 2rem;
    margin-bottom: 2rem;
}

.info-card h3 {
    margin-bottom: 1.5rem;
    color: var(--text);
    font-size: 1.25rem;
}

.facts-list {
    list-style: none;
}

.facts-list li {
    margin-bottom: 0.75rem;
    padding-left: 1.75rem;
    position: relative;
}

.facts-list li i {
    position: absolute;
    left: 0;
    top: 0.25rem;
    color: var(--primary);
}

/* FAQ */
.faq {
    margin-bottom: 3rem;
}

.faq h2 {
    text-align: center;
    margin-bottom: 1.5rem;
    font-size: 1.5rem;
    color: var(--text);
}

.faq-item {
    margin-bottom: 0.75rem;
    border: 1px solid var(--medium-gray);
    border-radius: var(--radius);
    overflow: hidden;
}

.faq-question {
    width: 100%;
    text-align: left;
    padding: 1rem 1.5rem;
    background: var(--white);
    border: none;
    font-size: 1rem;
    font-weight: 500;
    color: var(--text);
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: var(--transition);
}

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

.faq-question i {
    transition: var(--transition);
}

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

.faq-answer {
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease;
    background: var(--light-gray);
}

.faq-answer p {
    padding: 1.5rem;
    margin: 0;
    border-top: 1px solid var(--medium-gray);
}

/* Footer */
.footer {
    text-align: center;
    padding: 2rem 0;
    color: var(--text-light);
    font-size: 0.9rem;
}

.footer i {
    color: #ef4444;
    margin: 0 0.25rem;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Responsive */
@media (max-width: 768px) {
    .header {
        padding: 1.5rem 0;
    }

    h1 {
        font-size: 1.75rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .tabs {
        flex-wrap: nowrap;
        overflow-x: auto;
        padding-bottom: 0.5rem;
        -webkit-overflow-scrolling: touch;
    }

    .tab-btn {
        font-size: 0.85rem;
        padding: 0.6rem 1rem;
    }

    .card, .info-card {
        padding: 1.5rem;
    }

    .result .highlight {
        font-size: 1.2rem;
    }
}

/* Print Styles */
@media print {
    .tabs, .calculate-btn, .footer {
        display: none !important;
    }

    .tab-content {
        display: block !important;
        opacity: 1 !important;
    }

    .result {
        display: block !important;
        background: none;
        border: 1px solid #000;
    }
}