:root {
    --bg-primary: #111827;
    --bg-secondary: #1f2937;
    --bg-tertiary: #374151;
    --text-primary: #f9fafb;
    --text-secondary: #d1d5db;
    --border-color: #4b5563;
    --accent-blue: #3b82f6;
    --accent-blue-hover: #2563eb;
    --accent-green: #22c55e;
    --accent-green-hover: #16a34a;
    --accent-red: #ef4444;
    --accent-red-hover: #dc2626;
    --accent-yellow: #eab308;
    --accent-purple: #8b5cf6;
    --shadow-color: rgba(0, 0, 0, 0.2);
}

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

body {
    font-family: 'Inter', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
}

/* --- Layout --- */
.container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 2rem 1rem;
}

.main-grid {
    display: grid;
    grid-template-columns: 1fr;
    gap: 2rem;
}

@media (min-width: 1024px) {
    .main-grid {
        grid-template-columns: repeat(2, 1fr);
    }
}

/* --- General Components --- */
.card {
    background-color: var(--bg-secondary);
    padding: 1.5rem;
    border-radius: 12px;
    border: 1px solid var(--border-color);
    box-shadow: 0 4px 12px var(--shadow-color);
}

.card-title {
    font-size: 1.5rem;
    font-weight: 700;
    margin-bottom: 1.5rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border-color);
}

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

.form-label {
    display: block;
    font-size: 0.875rem;
    font-weight: 500;
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.form-input {
    width: 100%;
    background-color: var(--bg-tertiary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 0.75rem 1rem;
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-input:focus {
    outline: none;
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(59, 130, 246, 0.3);
}

.btn {
    width: 100%;
    padding: 0.75rem 1rem;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-primary);
    border: none;
    cursor: pointer;
    transition: background-color 0.2s, transform 0.1s;
}

.btn:active {
    transform: scale(0.98);
}

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

.btn-primary:hover {
    background-color: var(--accent-blue-hover);
}

.btn-success {
    background-color: var(--accent-green);
}

.btn-success:hover {
    background-color: var(--accent-green-hover);
}

/* --- Specific Components --- */
header {
    text-align: center;
    margin-bottom: 2.5rem;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 800;
}

header p {
    color: var(--text-secondary);
    font-size: 1.125rem;
    margin-top: 0.5rem;
}

.split-method-selector {
    display: flex;
    background-color: var(--bg-tertiary);
    border-radius: 8px;
    padding: 0.25rem;
}

.split-method-btn {
    flex: 1;
    padding: 0.5rem;
    border: none;
    background-color: transparent;
    color: var(--text-secondary);
    font-size: 0.875rem;
    font-weight: 500;
    border-radius: 6px;
    cursor: pointer;
    transition: background-color 0.2s, color 0.2s;
}

.split-method-btn.active {
    background-color: var(--accent-blue);
    color: var(--text-primary);
    font-weight: 600;
}

#person-value-container {
    transition: opacity 0.3s, max-height 0.3s;
    max-height: 0;
    opacity: 0;
    overflow: hidden;
}

#person-value-container.visible {
    max-height: 100px;
    opacity: 1;
}

.totals-summary {
    margin-top: 2rem;
    padding-top: 1.5rem;
    border-top: 1px solid var(--border-color);
}

.total-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 1.125rem;
    margin-bottom: 1rem;
}

.total-row span:first-child {
    font-weight: 500;
    color: var(--text-secondary);
}

.total-row span:last-child {
    font-weight: 700;
}

#display-total {
    color: var(--text-primary);
    font-size: 1.25rem;
}

#display-allocated {
    color: var(--accent-green);
}

#display-remaining {
    color: var(--accent-red);
}

#display-remaining.zero {
    color: var(--accent-green);
}

#display-remaining.over {
    color: var(--accent-yellow);
}

.people-list-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    background-color: var(--bg-tertiary);
    padding: 0.75rem 1rem;
    border-radius: 8px;
}

.person-info p:first-child {
    font-weight: 600;
}

.person-info p:last-child {
    font-size: 1.25rem;
    font-weight: 700;
    color: #67e8f9;
    /* cyan-300 */
}

.person-details {
    font-size: 0.875rem;
    color: var(--text-secondary);
    text-align: right;
    margin-left: 1rem;
}

.delete-person-btn {
    background-color: var(--accent-red);
    border: none;
    color: white;
    border-radius: 50%;
    width: 32px;
    height: 32px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    margin-left: 1rem;
    transition: background-color 0.2s, transform 0.2s;
    flex-shrink: 0;
}

.delete-person-btn:hover {
    background-color: var(--accent-red-hover);
    transform: scale(1.1);
}

#history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

#clear-history-btn {
    background: none;
    border: none;
    color: var(--accent-red);
    font-weight: 600;
    cursor: pointer;
    padding: 0.25rem;
}

#clear-history-btn:hover {
    text-decoration: underline;
}

.history-list {
    max-height: 80vh;
    overflow-y: auto;
    padding-right: 0.5rem;
    display: flex;
    flex-direction: column;
    gap: 1rem;
}

.history-card {
    background-color: var(--bg-tertiary);
    padding: 1rem;
    border-radius: 8px;
}

.history-card-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.75rem;
}

.history-card-header .total {
    font-size: 1.125rem;
    font-weight: 700;
}

.history-card-header .date {
    font-size: 0.75rem;
    color: var(--text-secondary);
}

.history-card-header .method-badge {
    font-size: 0.75rem;
    font-weight: 600;
    padding: 0.25rem 0.5rem;
    border-radius: 9999px;
    text-transform: uppercase;
}

.method-badge.equal {
    background-color: var(--accent-green);
    color: var(--bg-primary);
}

.method-badge.percentage {
    background-color: var(--accent-purple);
    color: var(--text-primary);
}

.method-badge.custom {
    background-color: var(--accent-yellow);
    color: var(--bg-primary);
}

.history-people-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.history-people-list li {
    display: flex;
    justify-content: space-between;
    font-size: 0.875rem;
}

.history-people-list li span:last-child {
    font-weight: 600;
    color: #a5f3fc;
    /* cyan-200 */
}

/* --- Custom Alert & Modal --- */
.alert-box {
    position: fixed;
    top: 20px;
    right: 20px;
    padding: 1rem 1.5rem;
    border-radius: 8px;
    color: white;
    font-weight: 600;
    z-index: 1000;
    opacity: 0;
    transform: translateY(-20px);
    transition: opacity 0.3s, transform 0.3s;
}

.alert-box.show {
    opacity: 1;
    transform: translateY(0);
}

.alert-box.error {
    background-color: var(--accent-red);
}

.alert-box.success {
    background-color: var(--accent-green);
}

.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    z-index: 998;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.3s, visibility 0.3s;
}

.modal-overlay.show {
    opacity: 1;
    visibility: visible;
}

.modal-content {
    background-color: var(--bg-secondary);
    padding: 2rem;
    border-radius: 12px;
    width: 90%;
    max-width: 400px;
    transform: scale(0.95);
    transition: transform 0.3s;
}

.modal-overlay.show .modal-content {
    transform: scale(1);
}

.modal-content h3 {
    margin-bottom: 1rem;
    font-size: 1.25rem;
}

.modal-content p {
    margin-bottom: 1.5rem;
    color: var(--text-secondary);
}

.modal-actions {
    display: flex;
    gap: 1rem;
}

.modal-actions .btn {
    flex: 1;
}

.btn-secondary {
    background-color: var(--bg-tertiary);
}

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

.btn-danger {
    background-color: var(--accent-red);
}

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