/* Improve touch interactions */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    -webkit-tap-highlight-color: transparent;
}

button {
    -webkit-tap-highlight-color: rgba(0, 0, 0, 0.1);
}

input[type="number"]::-webkit-inner-spin-button,
input[type="number"]::-webkit-outer-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

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

:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --danger-color: #dc2626;
    --danger-hover: #b91c1c;
    --success-color: #16a34a;
    --background: #f8fafc;
    --surface: #ffffff;
    --border: #e2e8f0;
    --text-primary: #1e293b;
    --text-secondary: #64748b;
    --positive: #16a34a;
    --negative: #dc2626;
    --shadow: 0 1px 3px 0 rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
    background: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    padding: 1rem;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    -webkit-tap-highlight-color: transparent;
}

.container {
    max-width: 900px;
    margin: 0 auto;
    background: var(--surface);
    border-radius: 12px;
    box-shadow: var(--shadow-lg);
    overflow: hidden;
}

/* Header */
header {
    background: var(--primary-color);
    color: white;
    padding: 2rem;
    text-align: center;
}

header h1 {
    font-size: 2rem;
    margin-bottom: 0.5rem;
}

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

/* Tabs */
.tabs {
    display: flex;
    background: var(--surface);
    border-bottom: 2px solid var(--border);
    overflow-x: auto;
}

.tab-button {
    flex: 1;
    padding: 1rem;
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    border-bottom: 3px solid transparent;
    white-space: nowrap;
}

.tab-button:hover {
    background: var(--background);
}

.tab-button.active {
    color: var(--primary-color);
    border-bottom-color: var(--primary-color);
}

/* Tab Content */
.tab-content {
    display: none;
    padding: 2rem;
}

.tab-content.active {
    display: block;
}

.tab-content h2 {
    margin-bottom: 1.5rem;
    color: var(--text-primary);
}

.tab-content h3 {
    margin: 1.5rem 0 1rem;
    color: var(--text-primary);
    font-size: 1.1rem;
}

.tab-content h4 {
    margin: 1rem 0 0.5rem;
    color: var(--text-secondary);
    font-size: 1rem;
    font-weight: 500;
}

/* Converter Mode (within Calculator) */
.exchange-info {
    text-align: center;
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: 2rem;
    padding: 0.75rem;
    background: var(--background);
    border-radius: 8px;
}

.converter-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    max-width: 500px;
    margin: 0 auto;
}

.converter-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.converter-group label {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 1.1rem;
}

.converter-group input {
    padding: 1rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1.5rem;
    text-align: center;
    font-weight: 500;
    background-color: var(--surface);
    color: var(--text-primary);
    -webkit-appearance: none;
}

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

.converter-arrow {
    text-align: center;
    font-size: 2rem;
    color: var(--primary-color);
    font-weight: bold;
}

/* Persons Tab */
.add-person-form {
    display: flex;
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

.add-person-form input {
    flex: 1;
    padding: 0.75rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
}

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

.add-person-form button {
    padding: 0.75rem 1.5rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.2s;
    white-space: nowrap;
}

.add-person-form button:hover {
    background: var(--primary-hover);
}

.persons-list {
    display: grid;
    gap: 0.75rem;
}

.person-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.person-item span {
    font-weight: 500;
}

.remove-btn {
    width: 28px;
    height: 28px;
    background: var(--danger-color);
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 1.25rem;
    cursor: pointer;
    transition: background 0.2s;
    display: flex;
    align-items: center;
    justify-content: center;
    line-height: 1;
}

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

/* Expense Tab */
.exchange-rate-section {
    background: var(--background);
    padding: 1rem;
    border-radius: 8px;
    margin-bottom: 1.5rem;
    display: flex;
    gap: 1rem;
    align-items: center;
}

.exchange-rate-section label {
    font-weight: 500;
    color: var(--text-secondary);
}

.exchange-rate-section input {
    width: 150px;
    padding: 0.5rem;
    border: 2px solid var(--border);
    border-radius: 6px;
    font-size: 1rem;
}

.mode-selection {
    margin-bottom: 1.5rem;
}

.mode-buttons {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
    gap: 0.75rem;
    margin-top: 0.75rem;
}

.mode-btn {
    padding: 0.75rem;
    background: var(--background);
    color: var(--text-secondary);
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

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

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

.expense-form {
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.form-group label {
    font-weight: 500;
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.form-group input,
.form-group select {
    padding: 0.875rem 0.75rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    height: 48px;
    line-height: 1.2;
    background-color: var(--surface);
    color: var(--text-primary);
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    box-sizing: border-box;
}

.form-group select {
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%231e293b' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 0.5rem center;
    background-size: 1.25rem;
    padding-right: 2rem;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.mode-content {
    display: none;
}

.mode-content.active {
    display: block;
}

/* Equal Mode */
.checkbox-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(150px, 1fr));
    gap: 0.75rem;
}

.checkbox-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.75rem;
    background: var(--background);
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.2s;
}

.checkbox-label:hover {
    background: #e0e7ff;
}

.checkbox-label input[type="checkbox"] {
    width: 18px;
    height: 18px;
    cursor: pointer;
}

/* Individual Mode */
.individual-inputs {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
}

.individual-input-row {
    display: grid;
    grid-template-columns: 1fr 2fr;
    gap: 1rem;
    align-items: center;
}

.individual-input-row label {
    font-weight: 500;
}

.individual-amount {
    padding: 0.75rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    background-color: var(--surface);
    color: var(--text-primary);
    -webkit-appearance: none;
}

/* Items Mode */
.items-list {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-bottom: 1rem;
}

.item-row {
    display: grid;
    grid-template-columns: 150px 1fr auto auto;
    gap: 0.75rem;
    align-items: start;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.item-row input,
.item-row select {
    padding: 0.875rem 0.75rem;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1rem;
    height: 48px;
    line-height: 1.2;
    background-color: var(--surface);
    color: var(--text-primary);
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    box-sizing: border-box;
}

.item-row select {
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%231e293b' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 0.5rem center;
    background-size: 1.25rem;
    padding-right: 2rem;
}

.item-person-container {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.item-person-single {
    width: 100%;
    background-color: var(--surface);
    color: var(--text-primary);
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    background-image: url("data:image/svg+xml;charset=UTF-8,%3csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%231e293b' stroke-width='2' stroke-linecap='round' stroke-linejoin='round'%3e%3cpolyline points='6 9 12 15 18 9'%3e%3c/polyline%3e%3c/svg%3e");
    background-repeat: no-repeat;
    background-position: right 0.5rem center;
    background-size: 1.25rem;
    padding: 0.875rem 2rem 0.875rem 0.75rem;
    line-height: 1.2;
    box-sizing: border-box;
}

.item-persons-multiple {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(120px, 1fr));
    gap: 0.5rem;
}

.item-person-checkbox {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.5rem;
    background: var(--surface);
    border-radius: 6px;
    cursor: pointer;
    transition: background 0.2s;
    font-size: 0.9rem;
}

.item-person-checkbox:hover {
    background: #e0e7ff;
}

.item-person-checkbox input[type="checkbox"] {
    width: 16px;
    height: 16px;
    cursor: pointer;
}

.toggle-multiple-btn {
    width: 48px;
    height: 48px;
    background: var(--background);
    color: var(--text-primary);
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 1.25rem;
    cursor: pointer;
    transition: all 0.2s;
    align-self: start;
}

.toggle-multiple-btn:hover {
    border-color: var(--primary-color);
    background: #e0e7ff;
}

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

.remove-item-btn {
    width: 48px;
    height: 48px;
    background: var(--danger-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1.25rem;
    cursor: pointer;
    transition: background 0.2s;
    align-self: start;
}

.remove-item-btn:hover {
    background: var(--danger-hover);
}

#add-item-btn {
    padding: 0.75rem;
    background: var(--background);
    color: var(--text-primary);
    border: 2px dashed var(--border);
    border-radius: 8px;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
}

#add-item-btn:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
}

.items-total {
    margin-top: 1rem;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
}

.total-comparison {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.total-comparison.match {
    color: var(--success-color);
}

.total-comparison.mismatch {
    color: var(--danger-color);
}

.total-comparison .error {
    font-weight: 600;
}

.total-comparison .success {
    font-weight: 600;
}

.submit-btn {
    padding: 1rem;
    background: var(--primary-color);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
    margin-top: 1rem;
}

.submit-btn:hover {
    background: var(--primary-hover);
}

.reset-btn {
    padding: 1rem;
    background: var(--text-secondary);
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background 0.2s;
    margin-top: 1.5rem;
    width: 100%;
}

.reset-btn:hover {
    background: var(--text-primary);
}

/* Result Section */
.result-section {
    margin-top: 2rem;
    padding: 1.5rem;
    background: var(--background);
    border-radius: 8px;
    border: 2px solid var(--primary-color);
}

.result-section h3 {
    color: var(--primary-color);
    margin-bottom: 1rem;
}

.error-text {
    color: var(--danger-color) !important;
}

.result-info {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
    padding: 1rem;
    background: var(--surface);
    border-radius: 8px;
    font-size: 1.1rem;
}

.result-total {
    display: flex;
    gap: 0.5rem;
    align-items: baseline;
}

.original-amount {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.split-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.split-item {
    display: flex;
    justify-content: space-between;
    padding: 0.75rem;
    background: var(--surface);
    border-radius: 6px;
    font-weight: 500;
}

/* Balance styles (used in results) */

.balance-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-top: 1rem;
}

.balance-item {
    display: flex;
    justify-content: space-between;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
    border: 1px solid var(--border);
    font-weight: 500;
}

.balance-item.positive {
    background: #dcfce7;
    border-color: var(--positive);
    color: var(--positive);
}

.balance-item.negative {
    background: #fee2e2;
    border-color: var(--negative);
    color: var(--negative);
}

.balance-item.zero {
    opacity: 0.6;
}

.transaction-list {
    display: flex;
    flex-direction: column;
    gap: 0.75rem;
    margin-top: 1rem;
}

.transaction-item {
    display: grid;
    grid-template-columns: 1fr auto 1fr auto;
    gap: 1rem;
    align-items: center;
    padding: 1rem;
    background: var(--background);
    border-radius: 8px;
    border: 1px solid var(--border);
}

.from-person {
    text-align: right;
    font-weight: 500;
}

.arrow {
    color: var(--primary-color);
    font-size: 1.25rem;
}

.to-person {
    font-weight: 500;
}

.amount {
    font-weight: 600;
    color: var(--primary-color);
    text-align: right;
}

.settlement-complete {
    padding: 2rem;
    background: #dcfce7;
    color: var(--success-color);
    border-radius: 8px;
    text-align: center;
    font-weight: 600;
    font-size: 1.1rem;
}

/* Empty States */
.empty-state {
    padding: 3rem;
    text-align: center;
    color: var(--text-secondary);
    font-style: italic;
}

/* Mobile Responsiveness */
@media (max-width: 768px) {
    body {
        padding: 0;
    }
    
    .container {
        border-radius: 0;
        min-height: 100vh;
    }
    
    header {
        padding: 1.25rem 1rem;
    }
    
    header h1 {
        font-size: 1.5rem;
    }
    
    .subtitle {
        font-size: 0.9rem;
    }
    
    .tab-content {
        padding: 1.25rem 1rem;
    }
    
    .tab-button {
        padding: 1rem 0.75rem;
        font-size: 0.9rem;
        min-height: 48px;
    }
    
    /* Make all interactive elements at least 44x44px (Apple guidelines) */
    button,
    input[type="checkbox"],
    select {
        min-height: 44px;
        min-width: 44px;
    }
    
    input[type="checkbox"] {
        width: 20px;
        height: 20px;
    }
    
    /* Converter Mode */
    .converter-group input {
        font-size: 1.75rem;
        padding: 1.25rem;
    }
    
    .converter-arrow {
        font-size: 2.5rem;
        margin: 0.5rem 0;
    }
    
    /* Mode Selection */
    .mode-buttons {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .mode-btn {
        padding: 1rem;
        font-size: 1rem;
    }
    
    /* Form Groups */
    .form-group input {
        font-size: 1rem;
        padding: 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    .form-group select {
        font-size: 1rem;
        padding: 1rem 2.5rem 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    /* Checkboxes */
    .checkbox-grid {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .checkbox-label {
        padding: 1.25rem;
        font-size: 1rem;
        min-height: 52px;
    }
    
    .checkbox-label input[type="checkbox"] {
        width: 20px;
        height: 20px;
        min-width: 20px;
        min-height: 20px;
    }
    
    /* Individual Mode */
    .individual-input-row {
        grid-template-columns: 1fr;
        gap: 0.5rem;
    }
    
    .individual-input-row label {
        font-size: 1rem;
    }
    
    .individual-amount {
        font-size: 1rem;
        padding: 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    /* Items Mode */
    .item-row {
        grid-template-columns: 1fr;
        gap: 0.75rem;
        padding: 1rem;
    }
    
    .item-row input {
        font-size: 1rem;
        padding: 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    .item-row select {
        font-size: 1rem;
        padding: 1rem 2.5rem 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    .item-person-container {
        width: 100%;
    }
    
    .item-person-single {
        font-size: 1rem;
        padding: 1rem 2.5rem 1rem 0.75rem;
        height: 52px;
        line-height: 1.2;
    }
    
    .item-persons-multiple {
        grid-template-columns: 1fr;
        gap: 0.75rem;
    }
    
    .item-person-checkbox {
        padding: 1rem;
        font-size: 1rem;
        min-height: 52px;
    }
    
    .item-person-checkbox input[type="checkbox"] {
        width: 20px;
        height: 20px;
        min-width: 20px;
        min-height: 20px;
    }
    
    .toggle-multiple-btn,
    .remove-item-btn {
        width: 100%;
        height: 52px;
        margin-top: 0.5rem;
        font-size: 1rem;
    }
    
    #add-item-btn {
        padding: 1rem;
        font-size: 1rem;
    }
    
    /* Result Section */
    .result-section {
        margin-top: 1.5rem;
        padding: 1rem;
    }
    
    .result-section h3 {
        font-size: 1.25rem;
    }
    
    .result-section h4 {
        font-size: 1.1rem;
    }
    
    .result-total {
        font-size: 1.1rem;
    }
    
    .split-item {
        padding: 1rem;
        font-size: 1rem;
    }
    
    .balance-item {
        padding: 1rem;
        font-size: 1rem;
    }
    
    .transaction-item {
        grid-template-columns: 1fr;
        gap: 0.75rem;
        text-align: left;
    }
    
    .from-person {
        text-align: left;
    }
    
    .arrow {
        display: inline;
        margin: 0 0.5rem;
    }
    
    .to-person {
        display: inline;
    }
    
    .amount {
        text-align: left;
        font-size: 1.1rem;
    }
    
    /* Person Management */
    .add-person-form {
        flex-direction: column;
        gap: 0.75rem;
    }
    
    .add-person-form input {
        font-size: 1rem;
        padding: 1rem;
    }
    
    .add-person-form button {
        width: 100%;
        padding: 1rem;
        font-size: 1rem;
    }
    
    .person-item {
        padding: 1rem;
        font-size: 1rem;
    }
    
    .remove-btn {
        width: 44px;
        height: 44px;
        font-size: 1.5rem;
    }
    
    /* Ensure proper spacing */
    .mode-content {
        margin-top: 1rem;
    }
    
    h2 {
        font-size: 1.5rem;
        margin-bottom: 1.25rem;
    }
    
    h3 {
        font-size: 1.25rem;
    }
    
    h4 {
        font-size: 1.1rem;
    }
}

@media (max-width: 480px) {
    header h1 {
        font-size: 1.35rem;
    }
    
    .tab-button {
        font-size: 0.85rem;
        padding: 0.875rem 0.5rem;
    }
    
    .converter-group input {
        font-size: 1.5rem;
    }
    
    .item-persons-multiple {
        grid-template-columns: 1fr;
    }
}