@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

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

:root {
    /* Vercel-Inspired Color Palette */
    --vercel-black: #000000;
    --vercel-bg: #fafafa;
    --vercel-fg: #000000;
    --vercel-gray: #666666;
    --vercel-light-gray: #999999;
    --vercel-lighter-gray: #eaeaea;
    --vercel-lightest-gray: #fafafa;
    --vercel-accent-1: #0070f3;
    --vercel-accent-2: #7928ca;
    --vercel-accent-3: #ff0080;
    --vercel-success: #0070f3;
    --vercel-error: #ee0000;

    /* Gradients */
    --gradient-1: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --gradient-2: linear-gradient(135deg, #f093fb 0%, #f5576c 100%);
    --gradient-vercel: linear-gradient(90deg, var(--vercel-accent-2) 0%, var(--vercel-accent-3) 100%);

    /* Shadows - Vercel style (very subtle) */
    --shadow-smallest: 0 2px 4px rgba(0, 0, 0, 0.04);
    --shadow-small: 0 5px 10px rgba(0, 0, 0, 0.08);
    --shadow-medium: 0 8px 30px rgba(0, 0, 0, 0.1);
    --shadow-large: 0 30px 60px rgba(0, 0, 0, 0.12);

    /* Borders */
    --border-color: #eaeaea;
    --border-radius: 8px;
    --border-radius-large: 12px;

    /* Spacing - Generous like Vercel */
    --space-4: 4px;
    --space-8: 8px;
    --space-12: 12px;
    --space-16: 16px;
    --space-24: 24px;
    --space-32: 32px;
    --space-48: 48px;
    --space-64: 64px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--vercel-bg);
    color: var(--vercel-fg);
    line-height: 1.6;
    padding: var(--space-24);
    font-size: 14px;
    letter-spacing: -0.02em;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

.container {
    max-width: 1280px;
    margin: 0 auto;
}

/* Header - Vercel Style */
header {
    text-align: center;
    margin-bottom: var(--space-64);
    padding: var(--space-48) var(--space-16);
    background: transparent;
}

header h1 {
    font-size: 48px;
    font-weight: 700;
    margin-bottom: var(--space-16);
    color: var(--vercel-fg);
    letter-spacing: -0.05em;
    background: var(--gradient-vercel);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    font-size: 24px;
    color: var(--vercel-fg);
    font-weight: 600;
    max-width: 800px;
    margin: 0 auto var(--space-12) auto;
    line-height: 1.6;
}

.subtitle-detail {
    font-size: 16px;
    color: var(--vercel-gray);
    font-weight: 400;
    max-width: 700px;
    margin: 0 auto;
    line-height: 1.7;
}

/* Sections - Vercel Style */
section {
    background: transparent;
    padding: 0;
    margin-bottom: var(--space-64);
}

section h2 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: var(--space-32);
    color: var(--vercel-fg);
    letter-spacing: -0.04em;
}

/* Card Selection - Vercel Cards */
.card-selection-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(450px, 1fr));
    gap: var(--space-32);
}

.card-selector {
    padding: 0;
}

.card-selector h3 {
    margin-bottom: var(--space-12);
    color: var(--vercel-gray);
    font-size: 14px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.card-select {
    width: 100%;
    padding: 14px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 16px;
    background: #ffffff;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    font-weight: 500;
    color: var(--vercel-fg);
    font-family: 'Inter', sans-serif;
}

.card-select:focus {
    outline: none;
    border-color: var(--vercel-accent-1);
    box-shadow: 0 0 0 3px rgba(0, 112, 243, 0.1);
}

.card-select:hover {
    border-color: var(--vercel-gray);
    box-shadow: var(--shadow-smallest);
}

.card-info {
    margin-top: var(--space-16);
    padding: var(--space-24);
    background: #ffffff;
    border-radius: var(--border-radius-large);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-small);
    min-height: 80px;
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.card-info:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-2px);
}

.card-detail h4 {
    font-size: 20px;
    margin-bottom: var(--space-12);
    color: var(--vercel-fg);
    font-weight: 700;
    letter-spacing: -0.03em;
}

.card-detail p {
    font-size: 16px;
    color: var(--vercel-gray);
    margin-bottom: var(--space-8);
    line-height: 1.6;
}

.fee-select {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 16px;
    background: #ffffff;
    margin-top: var(--space-12);
    cursor: pointer;
    font-family: 'Inter', sans-serif;
    transition: all 0.2s ease;
}

.fee-select:focus {
    outline: none;
    border-color: var(--vercel-accent-1);
    box-shadow: 0 0 0 3px rgba(0, 112, 243, 0.1);
}

.fee-select:hover {
    border-color: var(--vercel-gray);
}

.benefit-item {
    padding: var(--space-12) 0;
    background: transparent;
    margin-bottom: 0;
    font-size: 16px;
    border: none;
    border-bottom: 1px solid var(--border-color);
}

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

.benefit-category {
    font-weight: 600;
    color: var(--vercel-fg);
    margin-right: var(--space-8);
}

/* Spending Section - Vercel Grid */
.category-inputs {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: var(--space-24);
    margin-bottom: var(--space-32);
}

.category-input {
    padding: 0;
    background: transparent;
    transition: all 0.2s ease;
}

.category-input label {
    display: flex;
    align-items: center;
    gap: var(--space-8);
    margin-bottom: var(--space-8);
    font-weight: 500;
    color: var(--vercel-gray);
    font-size: 14px;
}

.category-icon {
    font-size: 16px;
}

.category-input input {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 16px;
    background: #ffffff;
    font-weight: 500;
    font-family: 'Inter', sans-serif;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.category-input input:focus {
    outline: none;
    border-color: var(--vercel-accent-1);
    box-shadow: 0 0 0 3px rgba(0, 112, 243, 0.1);
}

.category-input input:hover {
    border-color: var(--vercel-gray);
}

.total-spending {
    padding: var(--space-24) 0;
    background: transparent;
    text-align: right;
    font-size: 16px;
    border: none;
    border-top: 2px solid var(--vercel-fg);
    margin-top: var(--space-32);
}

.total-spending strong {
    display: inline;
    margin-right: var(--space-12);
    color: var(--vercel-fg);
    font-size: 16px;
    font-weight: 600;
}

.total-spending span {
    color: var(--vercel-accent-1);
    font-weight: 700;
    font-size: 24px;
    letter-spacing: -0.02em;
    font-family: 'Inter', monospace;
}

/* Action Section */
.action-section {
    text-align: center;
    margin: var(--space-64) 0;
}

/* Button - Vercel Gradient Style */
.btn-calculate {
    padding: 16px 48px;
    border: none;
    border-radius: var(--border-radius);
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    background: var(--vercel-fg);
    color: white;
    box-shadow: var(--shadow-small);
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    letter-spacing: -0.01em;
    font-family: 'Inter', sans-serif;
    position: relative;
    overflow: hidden;
}

.btn-calculate::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: var(--gradient-vercel);
    opacity: 0;
    transition: opacity 0.2s ease;
}

.btn-calculate:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-medium);
}

.btn-calculate:hover:not(:disabled)::before {
    opacity: 1;
}

.btn-calculate span {
    position: relative;
    z-index: 1;
}

.btn-calculate:active:not(:disabled) {
    transform: translateY(0);
}

.btn-calculate:disabled {
    opacity: 0.4;
    cursor: not-allowed;
    transform: none;
}

/* Result Section */
.result-section {
    animation: slideUp 0.5s cubic-bezier(0.4, 0, 0.2, 1);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.result-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(450px, 1fr));
    gap: var(--space-32);
    margin-bottom: var(--space-64);
}

.result-card {
    padding: var(--space-32);
    background: #ffffff;
    border-radius: var(--border-radius-large);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-small);
    transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

.result-card:hover {
    box-shadow: var(--shadow-medium);
    transform: translateY(-4px);
}

.result-card h3 {
    font-size: 24px;
    margin-bottom: var(--space-16);
    color: var(--vercel-fg);
    font-weight: 700;
    letter-spacing: -0.03em;
}

.result-card .total-benefit {
    font-size: 32px;
    font-weight: 700;
    background: var(--gradient-vercel);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin: var(--space-24) 0;
    text-align: center;
    padding: var(--space-24);
    background-color: var(--vercel-lightest-gray);
    border-radius: var(--border-radius-large);
    letter-spacing: -0.03em;
    font-family: 'Inter', monospace;
}

.benefit-breakdown {
    margin-top: var(--space-24);
}

.benefit-breakdown h4 {
    font-size: 14px;
    margin-bottom: var(--space-16);
    color: var(--vercel-light-gray);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.breakdown-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--space-12) 0;
    background: transparent;
    margin-bottom: 0;
    font-size: 16px;
    border: none;
    border-bottom: 1px solid var(--border-color);
}

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

.breakdown-category {
    font-weight: 500;
    color: var(--vercel-fg);
}

.breakdown-amount {
    color: var(--vercel-accent-1);
    font-weight: 600;
    font-family: 'Inter', monospace;
}

.annual-fee {
    margin-top: var(--space-16);
    padding: 12px 16px;
    background: #fffbeb;
    border-radius: var(--border-radius);
    text-align: center;
    font-size: 14px;
    color: #92400e;
    border: 1px solid #fde68a;
    font-weight: 500;
}

/* Result Summary - Vercel Hero */
.result-summary {
    padding: var(--space-48) var(--space-32);
    background: #ffffff;
    border-radius: var(--border-radius-large);
    text-align: center;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-small);
}

.result-summary h3 {
    font-size: 14px;
    margin-bottom: var(--space-24);
    color: var(--vercel-light-gray);
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.1em;
}

.winner {
    font-size: 40px;
    font-weight: 700;
    background: var(--gradient-vercel);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin: var(--space-16) 0;
    letter-spacing: -0.04em;
}

.difference {
    font-size: 18px;
    color: var(--vercel-gray);
    font-weight: 500;
    margin-top: var(--space-16);
}

.difference-amount {
    color: var(--vercel-accent-1);
    font-weight: 700;
    font-size: 24px;
    font-family: 'Inter', monospace;
}

/* About Section (SEO Content) */
.about-section {
    background: #ffffff;
    padding: var(--space-48) var(--space-32);
    border-radius: var(--border-radius-large);
    border: 1px solid var(--border-color);
    margin-bottom: var(--space-64);
}

.about-section h2 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: var(--space-24);
    color: var(--vercel-fg);
    letter-spacing: -0.04em;
}

.about-content p {
    font-size: 16px;
    line-height: 1.8;
    color: var(--vercel-gray);
    margin-bottom: var(--space-16);
}

.about-content strong {
    color: var(--vercel-fg);
    font-weight: 600;
}

/* Guide Section (SEO Content) */
.guide-section {
    background: #ffffff;
    padding: var(--space-48) var(--space-32);
    border-radius: var(--border-radius-large);
    border: 1px solid var(--border-color);
    margin-bottom: var(--space-64);
}

.guide-section h2 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: var(--space-32);
    color: var(--vercel-fg);
    letter-spacing: -0.04em;
}

.guide-steps {
    display: grid;
    gap: var(--space-24);
}

.guide-step {
    padding: var(--space-24);
    background: var(--vercel-lightest-gray);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
}

.guide-step h3 {
    font-size: 20px;
    font-weight: 700;
    color: var(--vercel-fg);
    margin-bottom: var(--space-12);
    letter-spacing: -0.02em;
}

.guide-step p {
    font-size: 16px;
    line-height: 1.7;
    color: var(--vercel-gray);
}

/* FAQ Section (AEO Optimization) */
.faq-section {
    background: #ffffff;
    padding: var(--space-48) var(--space-32);
    border-radius: var(--border-radius-large);
    border: 1px solid var(--border-color);
    margin-bottom: var(--space-64);
}

.faq-section h2 {
    font-size: 32px;
    font-weight: 700;
    margin-bottom: var(--space-32);
    color: var(--vercel-fg);
    letter-spacing: -0.04em;
}

.faq-list {
    display: grid;
    gap: var(--space-24);
}

.faq-item {
    padding: var(--space-24);
    background: var(--vercel-lightest-gray);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    transition: all 0.2s ease;
}

.faq-item:hover {
    box-shadow: var(--shadow-small);
    border-color: var(--vercel-gray);
}

.faq-item h3 {
    font-size: 18px;
    font-weight: 600;
    color: var(--vercel-fg);
    margin-bottom: var(--space-12);
    letter-spacing: -0.02em;
}

.faq-item p {
    font-size: 16px;
    line-height: 1.7;
    color: var(--vercel-gray);
}

/* Footer - Vercel Subtle */
footer {
    text-align: center;
    padding: var(--space-48);
    color: var(--vercel-light-gray);
    font-size: 14px;
    margin-top: var(--space-64);
    border-top: 1px solid var(--border-color);
}

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

/* Responsive Design - Vercel Approach */
@media (max-width: 768px) {
    body {
        padding: var(--space-16);
    }

    header {
        padding: var(--space-32) var(--space-16);
        margin-bottom: var(--space-48);
    }

    header h1 {
        font-size: 32px;
    }

    .subtitle {
        font-size: 16px;
    }

    section {
        margin-bottom: var(--space-48);
    }

    section h2 {
        font-size: 24px;
    }

    .card-selection-grid,
    .result-grid {
        grid-template-columns: 1fr;
        gap: var(--space-24);
    }

    .category-inputs {
        grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
        gap: var(--space-16);
    }

    .btn-calculate {
        width: 100%;
        padding: 14px 32px;
    }

    .result-summary {
        padding: var(--space-32) var(--space-24);
    }

    .winner {
        font-size: 32px;
    }

    .result-card .total-benefit {
        font-size: 24px;
    }

    /* SEO Content Sections - Mobile */
    .about-section,
    .guide-section,
    .faq-section {
        padding: var(--space-32) var(--space-24);
        margin-bottom: var(--space-48);
    }

    .about-section h2,
    .guide-section h2,
    .faq-section h2 {
        font-size: 24px;
    }

    .guide-step h3,
    .faq-item h3 {
        font-size: 16px;
    }

    .about-content p,
    .guide-step p,
    .faq-item p {
        font-size: 14px;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 28px;
    }

    section h2 {
        font-size: 20px;
    }

    .category-inputs {
        grid-template-columns: 1fr;
    }

    .total-spending span {
        font-size: 20px;
    }

    .winner {
        font-size: 28px;
    }

    /* SEO Content Sections - Small Mobile */
    .about-section,
    .guide-section,
    .faq-section {
        padding: var(--space-24) var(--space-16);
    }

    .about-section h2,
    .guide-section h2,
    .faq-section h2 {
        font-size: 20px;
    }
}