introducing tooltips

frontend/styles.css

@@ -1389,10 +1389,135 @@ body {
         margin: 1rem;
         max-height: calc(100vh - 2rem);
     }
-    
+
     .rankings-controls {
         flex-direction: column;
         align-items: stretch;
     }
 }
 
+/* =============================================================================
+   TOOLTIP SYSTEM
+   ============================================================================= */
+
+/* Info Icon Trigger */
+.info-trigger {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    padding: 0;
+    margin-left: 0.25rem;
+    background: none;
+    border: none;
+    cursor: help;
+    color: var(--text-muted);
+    opacity: 0.6;
+    transition: var(--transition);
+    vertical-align: middle;
+    border-radius: 50%;
+}
+
+.info-trigger:hover,
+.info-trigger:focus {
+    color: var(--accent-teal);
+    opacity: 1;
+}
+
+.info-trigger:focus {
+    outline: none;
+    box-shadow: 0 0 0 2px var(--accent-teal);
+}
+
+.info-trigger:focus:not(:focus-visible) {
+    box-shadow: none;
+}
+
+.info-trigger:focus-visible {
+    box-shadow: 0 0 0 2px var(--accent-teal);
+}
+
+/* Info Icon SVG */
+.info-icon {
+    width: 12px;
+    height: 12px;
+    flex-shrink: 0;
+}
+
+.modal-stat-label .info-icon {
+    width: 14px;
+    height: 14px;
+}
+
+/* Tooltip Container */
+.tooltip {
+    position: absolute;
+    z-index: 3000;
+    min-width: 200px;
+    max-width: 280px;
+    padding: 0.75rem 1rem;
+    background: var(--bg-accent);
+    color: var(--text-inverse);
+    border-radius: var(--radius-md);
+    box-shadow: var(--shadow-medium);
+    font-family: 'DM Sans', sans-serif;
+    font-size: 0.8125rem;
+    line-height: 1.5;
+    text-transform: none;
+    letter-spacing: normal;
+    text-align: left;
+    opacity: 0;
+    visibility: hidden;
+    transition: opacity 150ms ease, visibility 150ms ease;
+    pointer-events: none;
+}
+
+.tooltip.visible {
+    opacity: 1;
+    visibility: visible;
+    pointer-events: auto;
+}
+
+/* Tooltip Arrow - Top Placement (arrow points down) */
+.tooltip[data-placement="top"]::after {
+    content: '';
+    position: absolute;
+    top: 100%;
+    left: 50%;
+    transform: translateX(-50%);
+    border: 8px solid transparent;
+    border-top-color: var(--bg-accent);
+}
+
+/* Tooltip Arrow - Bottom Placement (arrow points up) */
+.tooltip[data-placement="bottom"]::after {
+    content: '';
+    position: absolute;
+    bottom: 100%;
+    left: 50%;
+    transform: translateX(-50%);
+    border: 8px solid transparent;
+    border-bottom-color: var(--bg-accent);
+}
+
+/* Tooltip Title */
+.tooltip-title {
+    font-weight: 600;
+    margin-bottom: 0.25rem;
+    font-size: 0.875rem;
+}
+
+/* Tooltip Note (for context like national average) */
+.tooltip-note {
+    margin-top: 0.5rem;
+    padding-top: 0.5rem;
+    border-top: 1px solid rgba(250, 247, 242, 0.2);
+    font-size: 0.75rem;
+    opacity: 0.8;
+}
+
+/* Label wrapper for inline icon */
+.stat-label-with-info {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+}