/* ============================================================
   CDO Tranche Simulation — Professional White Interface
   ============================================================ */

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

body {
    font-family: -apple-system, "Segoe UI", Helvetica, Arial, sans-serif;
    background: #ffffff;
    color: #1a1a1a;
    line-height: 1.5;
    font-size: 14px;
}

/* --- Header --- */

.site-header {
    border-bottom: 1px solid #d0d0d0;
    padding: 18px 32px;
    display: flex;
    align-items: baseline;
    gap: 16px;
}

.site-header h1 {
    font-family: Georgia, "Times New Roman", serif;
    font-size: 20px;
    font-weight: normal;
    letter-spacing: 0.02em;
    color: #1a1a1a;
}

.site-header .subtitle {
    font-size: 12px;
    color: #888;
}

/* --- Tab Navigation --- */

.tab-nav {
    display: flex;
    border-bottom: 1px solid #d0d0d0;
    padding: 0 32px;
    gap: 0;
    background: #fafafa;
}

.tab-nav button {
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    padding: 10px 20px;
    font-size: 13px;
    color: #666;
    cursor: pointer;
    font-family: inherit;
    transition: color 0.15s, border-color 0.15s;
    white-space: nowrap;
}

.tab-nav button:hover {
    color: #1a1a1a;
}

.tab-nav button.active {
    color: #1a1a1a;
    border-bottom-color: #1a1a1a;
    font-weight: 600;
}

/* --- Content Panels --- */

.tab-panel {
    display: none;
    padding: 28px 32px;
    max-width: 1100px;
}

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

.panel-title {
    font-family: Georgia, "Times New Roman", serif;
    font-size: 17px;
    font-weight: normal;
    margin-bottom: 4px;
    color: #1a1a1a;
}

.panel-desc {
    font-size: 12px;
    color: #777;
    margin-bottom: 20px;
}

/* --- Forms --- */

.param-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
    gap: 12px 20px;
    margin-bottom: 20px;
}

.param-group {
    display: flex;
    flex-direction: column;
    gap: 3px;
}

.param-group label {
    font-size: 11px;
    color: #555;
    text-transform: uppercase;
    letter-spacing: 0.05em;
}

.param-group input,
.param-group select {
    padding: 7px 10px;
    border: 1px solid #ccc;
    border-radius: 3px;
    font-size: 13px;
    font-family: inherit;
    background: #f9f9f9;
    color: #1a1a1a;
    transition: border-color 0.15s;
}

.param-group input:focus,
.param-group select:focus {
    outline: none;
    border-color: #888;
    background: #fff;
}

.param-group textarea {
    padding: 7px 10px;
    border: 1px solid #ccc;
    border-radius: 3px;
    font-size: 12px;
    font-family: "SFMono-Regular", Consolas, "Liberation Mono", Menlo, monospace;
    background: #f9f9f9;
    color: #1a1a1a;
    resize: vertical;
    min-height: 80px;
    transition: border-color 0.15s;
}

.param-group textarea:focus {
    outline: none;
    border-color: #888;
    background: #fff;
}

.param-group.wide {
    grid-column: 1 / -1;
}

/* --- Buttons --- */

.btn {
    display: inline-block;
    padding: 8px 24px;
    border: 1px solid #333;
    background: #1a1a1a;
    color: #fff;
    font-size: 13px;
    font-family: inherit;
    border-radius: 3px;
    cursor: pointer;
    transition: background 0.15s;
    margin-bottom: 24px;
}

.btn:hover {
    background: #333;
}

.btn:disabled {
    background: #999;
    border-color: #999;
    cursor: not-allowed;
}

/* --- Charts --- */

.chart-container {
    position: relative;
    width: 100%;
    height: 380px;
    margin-bottom: 24px;
    border: 1px solid #e8e8e8;
    border-radius: 3px;
    padding: 12px;
    background: #fff;
}

/* --- Stats / Tables --- */

.stats-container {
    margin-top: 8px;
}

.stats-container table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13px;
}

.stats-container th,
.stats-container td {
    text-align: left;
    padding: 7px 12px;
    border-bottom: 1px solid #e8e8e8;
}

.stats-container th {
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: #777;
    font-weight: 600;
    background: #fafafa;
}

.stats-container tr:last-child td {
    border-bottom: none;
}

.stats-container tr.highlight td {
    font-weight: 600;
    background: #f5f5f0;
}

.stats-container .delta {
    font-size: 11px;
    color: #999;
}

/* --- Footer --- */

.site-footer {
    border-top: 1px solid #e0e0e0;
    padding: 14px 32px;
    font-size: 11px;
    color: #aaa;
    margin-top: 40px;
}

/* --- Responsive --- */

@media (max-width: 700px) {
    .site-header { padding: 14px 16px; }
    .tab-nav { padding: 0 8px; overflow-x: auto; }
    .tab-nav button { padding: 8px 12px; font-size: 12px; }
    .tab-panel { padding: 20px 16px; }
    .param-grid { grid-template-columns: 1fr 1fr; }
}