diff --git a/src/server/request-handler.ts b/src/server/request-handler.ts
index 71ef695..3b38361 100644
--- a/src/server/request-handler.ts
+++ b/src/server/request-handler.ts
@@ -838,6 +838,38 @@ function htmlPage(): string {
         box-shadow: none;
       }
 
+      .timeline-selection,
+      .timeline-brush {
+        position: absolute;
+        top: 4px;
+        bottom: 18px;
+        left: 0;
+        width: 0;
+        opacity: 0;
+        pointer-events: none;
+        transition: opacity 120ms ease, background 120ms ease, border-color 120ms ease;
+      }
+
+      .timeline-selection {
+        background: var(--timeline-selection-bg);
+        border: 1px solid var(--timeline-selection-border);
+        z-index: 0;
+      }
+
+      .timeline-selection.visible {
+        opacity: 1;
+      }
+
+      .timeline-brush {
+        background: var(--timeline-brush-bg);
+        border: 1px solid var(--timeline-brush-border);
+        z-index: 2;
+      }
+
+      .timeline-brush.visible {
+        opacity: 1;
+      }
+
       .timeline-chart::before {
         content: none;
       }