/* ============================
   CSS Custom Properties (Tokens)
   ============================ */
:root {
    /* Colors */
    --color-primary: #6366f1;
    --color-primary-dark: #4f46e5;
    --color-primary-light: #818cf8;
    --color-secondary: #64748b;
    --color-success: #22c55e;
    --color-danger: #ef4444;
    --color-warning: #f59e0b;

    /* Background & Surface */
    --bg-main: #0f172a;
    --bg-card: #1e293b;
    --bg-card-hover: #334155;
    --bg-input: #0f172a;

    /* Text */
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;

    /* Borders */
    --border-color: #334155;
    --border-radius: 12px;
    --border-radius-sm: 8px;

    /* Shadows */
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.3);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.4);

    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;

    /* Transitions */
    --transition-fast: 150ms ease;
    --transition-normal: 250ms ease;
}

/* ============================
   Reset & Base
   ============================ */
*,
*::before,
*::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg-main);
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
}

/* ============================
   Layout
   ============================ */
.app-container {
    max-width: 800px;
    margin: 0 auto;
    padding: var(--spacing-md);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    gap: var(--spacing-lg);
}

/* ============================
   Header
   ============================ */
.app-header {
    text-align: center;
    padding: var(--spacing-xl) 0;
}

.app-header h1 {
    font-size: 2rem;
    font-weight: 700;
    background: linear-gradient(135deg, var(--color-primary-light), var(--color-primary));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--spacing-xs);
}

.app-header .subtitle {
    color: var(--text-secondary);
    font-size: 1rem;
}

/* ============================
   Cards
   ============================ */
.card {
    background: var(--bg-card);
    border-radius: var(--border-radius);
    border: 1px solid var(--border-color);
    overflow: hidden;
    transition: transform var(--transition-normal), box-shadow var(--transition-normal);
}

.card:hover {
    box-shadow: var(--shadow-lg);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md) var(--spacing-lg);
    border-bottom: 1px solid var(--border-color);
    background: rgba(99, 102, 241, 0.05);
}

.card-header h2 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

.card-body {
    padding: var(--spacing-lg);
}

/* ============================
   Buttons
   ============================ */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-xs);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.875rem;
    font-weight: 500;
    border: none;
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: all var(--transition-fast);
}

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

.btn-primary:hover {
    background: var(--color-primary-dark);
    transform: translateY(-1px);
}

.btn-secondary {
    background: var(--bg-card-hover);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background: var(--border-color);
}

.btn-danger {
    background: rgba(239, 68, 68, 0.1);
    color: var(--color-danger);
    border: 1px solid rgba(239, 68, 68, 0.3);
}

.btn-danger:hover {
    background: var(--color-danger);
    color: white;
}

.btn-calculate {
    background: linear-gradient(135deg, var(--color-primary), var(--color-primary-dark));
    color: white;
    padding: var(--spacing-md) var(--spacing-xl);
    font-size: 1.1rem;
    font-weight: 600;
    width: 100%;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow-md);
}

.btn-calculate:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

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

/* ============================
   Form Elements
   ============================ */
.form-row {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: var(--spacing-md);
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-xs);
}

.form-group label {
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
}

input[type="text"],
input[type="number"] {
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 1rem;
    color: var(--text-primary);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

input:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

input::placeholder {
    color: var(--text-muted);
}

/* ============================
   Roommates Section
   ============================ */
.roommates-list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.roommate-tag {
    display: inline-flex;
    align-items: center;
    gap: var(--spacing-sm);
    background: rgba(99, 102, 241, 0.15);
    color: var(--color-primary-light);
    padding: var(--spacing-sm) var(--spacing-md);
    border-radius: 20px;
    font-weight: 500;
    animation: fadeIn 0.3s ease;
}

.roommate-tag .remove-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 0;
    font-size: 1.2rem;
    line-height: 1;
    transition: color var(--transition-fast);
}

.roommate-tag .remove-btn:hover {
    color: var(--color-danger);
}

.add-roommate-form {
    display: flex;
    gap: var(--spacing-sm);
}

.add-roommate-form input {
    flex: 1;
}

/* ============================
   Invoice Section
   ============================ */
.invoices-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.invoice-item {
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    animation: fadeIn 0.3s ease;
}

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

.invoice-name-input {
    flex: 1;
    font-weight: 600;
    background: transparent;
    border: 1px solid transparent;
    color: var(--color-primary-light);
    font-size: 1rem;
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
}

.invoice-name-input:hover,
.invoice-name-input:focus {
    background: var(--bg-card);
    border-color: var(--border-color);
}

.invoice-details {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-sm);
}

.invoice-summary {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
    padding-top: var(--spacing-sm);
    border-top: 1px dashed var(--border-color);
}

.days-badge {
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-xs) var(--spacing-sm);
    background: rgba(99, 102, 241, 0.15);
    color: var(--color-primary-light);
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
}

.daily-cost-badge {
    display: inline-flex;
    align-items: center;
    padding: var(--spacing-xs) var(--spacing-sm);
    background: rgba(34, 197, 94, 0.15);
    color: var(--color-success);
    border-radius: 12px;
    font-size: 0.8rem;
    font-weight: 500;
}

.invoices-total {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: rgba(99, 102, 241, 0.1);
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: var(--border-radius-sm);
    margin-top: var(--spacing-md);
}

.invoices-total .label {
    font-weight: 500;
    color: var(--text-secondary);
}

.invoices-total .value {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--color-primary-light);
}

.empty-message {
    color: var(--text-muted);
    font-size: 0.9rem;
    text-align: center;
    padding: var(--spacing-lg);
    background: var(--bg-input);
    border-radius: var(--border-radius-sm);
    border: 1px dashed var(--border-color);
}

.empty-message.default-info {
    color: var(--color-success);
    border-color: rgba(34, 197, 94, 0.3);
    background: rgba(34, 197, 94, 0.1);
}

.section-hint {
    color: var(--text-muted);
    font-size: 0.85rem;
    margin-bottom: var(--spacing-md);
}

/* ============================
   Adjustments Section
   ============================ */
.adjustments-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-sm);
}

.adjustment-item {
    display: grid;
    grid-template-columns: 1fr auto auto auto;
    gap: var(--spacing-sm);
    align-items: center;
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    animation: fadeIn 0.3s ease;
}

.adjustment-item input[type="text"] {
    background: transparent;
    border: none;
    color: var(--text-primary);
    font-size: 0.9rem;
}

.adjustment-item input[type="text"]:focus {
    outline: none;
    background: var(--bg-card);
}

.adjustment-item input[type="number"] {
    width: 100px;
    text-align: right;
}

.adjustment-item select {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-xs) var(--spacing-sm);
    color: var(--text-primary);
    font-size: 0.875rem;
}

.adjustment-amount {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
}

.adjustment-amount.positive input {
    color: var(--color-success);
}

.adjustment-amount.negative input {
    color: var(--color-danger);
}

@media (max-width: 600px) {
    .adjustment-item {
        grid-template-columns: 1fr;
        gap: var(--spacing-xs);
    }

    .invoice-details {
        grid-template-columns: 1fr 1fr;
        gap: var(--spacing-xs);
    }

    .invoice-details>*:last-child {
        grid-column: 1 / -1;
    }

    .invoice-header {
        flex-wrap: wrap;
    }

    .invoice-name-input {
        min-width: 120px;
    }
}

/* Date inputs */
input[type="date"] {
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm) var(--spacing-md);
    font-size: 0.9rem;
    color: var(--text-primary);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    color-scheme: dark;
    width: 100%;
    min-width: 0;
    box-sizing: border-box;
}

input[type="date"]:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.2);
}

.period-dates {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--spacing-sm);
    margin-bottom: var(--spacing-md);
}

.daily-cost {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    background: rgba(34, 197, 94, 0.1);
    border-radius: var(--border-radius-sm);
    border: 1px solid rgba(34, 197, 94, 0.2);
}

.daily-cost .label {
    color: var(--text-secondary);
}

.daily-cost .value {
    font-weight: 600;
    color: var(--color-success);
}

/* ============================
   Periods Section
   ============================ */
.periods-list {
    display: flex;
    flex-direction: column;
    gap: var(--spacing-md);
}

.period-item {
    background: var(--bg-input);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    animation: fadeIn 0.3s ease;
}

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

.period-header h3 {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--color-primary-light);
}

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

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

.period-days input {
    width: 80px;
    text-align: center;
}

.period-presence {
    margin-bottom: var(--spacing-md);
}

.period-presence-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    display: block;
}

.presence-checkboxes {
    display: flex;
    flex-wrap: wrap;
    gap: var(--spacing-sm);
}

.presence-checkbox {
    display: flex;
    align-items: center;
    gap: var(--spacing-xs);
    background: var(--bg-card);
    padding: var(--spacing-xs) var(--spacing-sm);
    border-radius: var(--border-radius-sm);
    cursor: pointer;
    transition: background var(--transition-fast);
}

.presence-checkbox:hover {
    background: var(--bg-card-hover);
}

.presence-checkbox input[type="checkbox"] {
    accent-color: var(--color-primary);
}

.presence-checkbox span {
    font-size: 0.875rem;
}

.period-guests {
    border-top: 1px dashed var(--border-color);
    padding-top: var(--spacing-md);
}

.period-guests-label {
    font-size: 0.875rem;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-sm);
    display: block;
}

.guest-row {
    display: flex;
    gap: var(--spacing-sm);
    align-items: center;
    flex-wrap: wrap;
}

.guest-row input[type="number"] {
    width: 60px;
    text-align: center;
}

.guest-row select {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-sm);
    color: var(--text-primary);
    font-size: 0.875rem;
}

.guest-row label {
    font-size: 0.875rem;
    color: var(--text-secondary);
}

.days-summary {
    display: flex;
    align-items: center;
    gap: var(--spacing-sm);
    margin-top: var(--spacing-md);
    padding: var(--spacing-md);
    background: var(--bg-input);
    border-radius: var(--border-radius-sm);
    font-size: 0.9rem;
}

.days-summary .used {
    color: var(--text-secondary);
}

.days-summary .used strong {
    color: var(--color-primary-light);
}

.days-summary .separator {
    color: var(--text-muted);
}

.days-summary .total strong {
    color: var(--text-primary);
}

.days-summary.error .used strong {
    color: var(--color-danger);
}

.days-summary.complete .used strong {
    color: var(--color-success);
}

/* ============================
   Calculate Section
   ============================ */
.calculate-section {
    padding: var(--spacing-sm) 0;
}

/* ============================
   Results Section
   ============================ */
.results-card {
    border-color: var(--color-success);
    animation: fadeIn 0.4s ease;
}

.results-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.result-item {
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(99, 102, 241, 0.05));
    border: 1px solid rgba(99, 102, 241, 0.2);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    text-align: center;
}

.result-item .name {
    font-size: 1rem;
    font-weight: 600;
    color: var(--color-primary-light);
    margin-bottom: var(--spacing-xs);
}

.result-item .amount {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--text-primary);
}

.results-total {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: var(--spacing-md);
    background: rgba(34, 197, 94, 0.1);
    border: 1px solid rgba(34, 197, 94, 0.2);
    border-radius: var(--border-radius-sm);
    margin-bottom: var(--spacing-lg);
}

.results-total .label {
    font-weight: 500;
    color: var(--text-secondary);
}

.results-total .value {
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--color-success);
}

.results-breakdown {
    border-top: 1px solid var(--border-color);
    padding-top: var(--spacing-md);
}

.results-breakdown h3 {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
}

.breakdown-period {
    background: var(--bg-input);
    border-radius: var(--border-radius-sm);
    padding: var(--spacing-md);
    margin-bottom: var(--spacing-sm);
}

.breakdown-period-header {
    display: flex;
    justify-content: space-between;
    margin-bottom: var(--spacing-sm);
    font-size: 0.875rem;
}

.breakdown-period-header .period-name {
    font-weight: 500;
    color: var(--color-primary-light);
}

.breakdown-period-header .period-cost {
    color: var(--text-secondary);
}

.breakdown-details {
    font-size: 0.8rem;
    color: var(--text-muted);
}

.results-actions {
    margin-top: var(--spacing-lg);
    padding-top: var(--spacing-md);
    border-top: 1px solid var(--border-color);
    text-align: center;
}

.results-actions .btn {
    gap: var(--spacing-xs);
}

/* ============================
   Footer
   ============================ */
.app-footer {
    text-align: center;
    padding: var(--spacing-xl) 0 var(--spacing-md);
    color: var(--text-muted);
    font-size: 0.875rem;
}

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

    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* ============================
   Responsive
   ============================ */
@media (max-width: 600px) {
    .app-header h1 {
        font-size: 1.6rem;
    }

    .card-header {
        flex-direction: column;
        gap: var(--spacing-sm);
        text-align: center;
    }

    .period-days {
        flex-wrap: wrap;
    }

    .guest-row {
        flex-direction: column;
        align-items: flex-start;
    }
}