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

:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --background: #f8fafc;
    --card-background: #ffffff;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --border-color: #e2e8f0;
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1), 0 1px 2px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1), 0 4px 6px -4px rgb(0 0 0 / 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    min-height: 100vh;
    padding: 20px;
    color: var(--text-primary);
}

.container {
    max-width: 600px;
    margin: 0 auto;
}

header {
    text-align: center;
    color: white;
    margin-bottom: 30px;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 8px;
}

.subtitle {
    font-size: 1rem;
    opacity: 0.9;
}

main {
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.card {
    background: var(--card-background);
    border-radius: 16px;
    padding: 24px;
    box-shadow: var(--shadow-lg);
}

.card h2 {
    font-size: 1.25rem;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

/* People Selector */
.people-selector {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 8px;
}

.btn-people {
    padding: 12px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-primary);
}

.btn-people:hover {
    border-color: var(--primary-color);
    transform: translateY(-2px);
}

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

.input-custom {
    grid-column: span 5;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 1rem;
    width: 100%;
    transition: border-color 0.2s;
}

.input-custom:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Toggle Group */
.toggle-group {
    display: flex;
    gap: 8px;
    margin-bottom: 16px;
}

.btn-toggle {
    flex: 1;
    padding: 12px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-primary);
}

.btn-toggle:hover {
    border-color: var(--primary-color);
}

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

/* Amount Input */
.amount-input-wrapper {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 16px;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    background: var(--background);
}

.currency {
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.input-amount {
    flex: 1;
    border: none;
    background: transparent;
    font-size: 1.5rem;
    font-weight: 600;
    color: var(--text-primary);
    outline: none;
}

.amount-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    white-space: nowrap;
}

/* Tax Selector */
.tax-selector {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
}

.btn-tax {
    padding: 12px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-primary);
}

.btn-tax:hover {
    border-color: var(--secondary-color);
    transform: translateY(-2px);
}

.btn-tax.active {
    background: var(--secondary-color);
    color: white;
    border-color: var(--secondary-color);
}

.input-custom-small {
    grid-column: span 3;
    padding: 12px;
    border: 2px solid var(--border-color);
    border-radius: 8px;
    font-size: 0.95rem;
    width: 100%;
    transition: border-color 0.2s;
}

.input-custom-small:focus {
    outline: none;
    border-color: var(--secondary-color);
}

/* Tip Selector */
.tip-selector {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 8px;
}

.btn-tip {
    padding: 12px;
    border: 2px solid var(--border-color);
    background: white;
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    color: var(--text-primary);
}

.btn-tip:hover {
    border-color: var(--success-color);
    transform: translateY(-2px);
}

.btn-tip.active {
    background: var(--success-color);
    color: white;
    border-color: var(--success-color);
}

/* Summary */
.summary-card {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
}

.summary-card h2 {
    color: white;
}

.summary-details {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 24px;
}

.summary-row {
    display: flex;
    justify-content: space-between;
    font-size: 1rem;
    padding: 8px 0;
}

.total-row {
    border-top: 2px solid rgba(255, 255, 255, 0.3);
    padding-top: 16px;
    margin-top: 8px;
    font-size: 1.125rem;
    font-weight: 600;
}

.per-person-result {
    background: rgba(255, 255, 255, 0.2);
    border-radius: 12px;
    padding: 20px;
    text-align: center;
    backdrop-filter: blur(10px);
}

.per-person-label {
    font-size: 0.875rem;
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 8px;
    opacity: 0.9;
}

.per-person-amount {
    font-size: 2.5rem;
    font-weight: 700;
    color: white;
}

footer {
    text-align: center;
    color: white;
    margin-top: 30px;
    opacity: 0.8;
    font-size: 0.875rem;
}

/* Responsive Design */
@media (max-width: 640px) {
    header h1 {
        font-size: 2rem;
    }

    .people-selector {
        grid-template-columns: repeat(3, 1fr);
    }

    .input-custom {
        grid-column: span 3;
    }

    .tax-selector,
    .tip-selector {
        grid-template-columns: repeat(2, 1fr);
    }

    .input-custom-small {
        grid-column: span 2;
    }

    .per-person-amount {
        font-size: 2rem;
    }
}

/* Remove spinner from number inputs */
input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

input[type="number"] {
    appearance: textfield;
    -moz-appearance: textfield;
}