diff --git a/frontend/components/MultiplayerPanel.js b/frontend/components/MultiplayerPanel.js
index 9062f42977..4c3447c618 100644
--- a/frontend/components/MultiplayerPanel.js
+++ b/frontend/components/MultiplayerPanel.js
@@ -6,6 +6,7 @@ import { PlutoActionsContext } from "../common/PlutoContext.js"
 // TODO: investigate why effect is bad with low throttle rate?
 // ....  update notebook should be pretty fast.
 const CURSOR_THROTTLE_RATE = 100
+const DEFAULT_CURSOR_COLOR = "#eeeeee"
 
 const mouse_data_to_point = ({relative_to_cell, relative_x, relative_y}) => {
     const cell_elt = document.getElementById(relative_to_cell)
@@ -21,6 +22,9 @@ const mouse_data_to_point = ({relative_to_cell, relative_x, relative_y}) => {
     ]
 }
 
+// l² norm in pixel space
+const dist2 = (x1, y1, x2, y2) => (x1 - x2) ^ 2 + (y1 - y2) ^ 2
+
 const update_mouse_data = (mouseX, mouseY) => {
     const cell_nodes = Array.from(document.querySelectorAll("pluto-notebook > pluto-cell"))
 
@@ -31,13 +35,13 @@ const update_mouse_data = (mouseX, mouseY) => {
 
     const mousePt = [mouseX, mouseY]
 
-    for (let cell_elt of cell_nodes) {
-        const dist_with_cell = dist2(mousePt, [cell_elt.offsetLeft, cell_elt.offsetTop])
+    for (let { id: cell_id, offsetLeft: cell_x, offsetTop: cell_y } of cell_nodes) {
+        const dist_with_cell = dist2(mouseX, mouseY, cell_x, cell_y)
         if (dist_with_cell < best_dist) {
             best_dist = dist_with_cell
-            best_index = cell_elt.id
-            relative_x = mouseX - cell_elt.offsetLeft
-            relative_y = mouseY - cell_elt.offsetTop
+            best_index = cell_id
+            relative_x = mouseX - cell_x
+            relative_y = mouseY - cell_y
         }
     }
 
@@ -60,8 +64,8 @@ const usePerfectCursor = (cb, point) => {
     return onPointChange
 }
 
+// hex needs to be a string of length 7 example: '#bedbad'
 const hexToRGBA = (hex, alpha) => `rgba(${parseInt(hex.slice(1,3),16)},${parseInt(hex.slice(3,5),16)},${parseInt(hex.slice(5,8),16)},${alpha})`
-const dist2 = ([x1,y1], [x2,y2]) => (x1 - x2) ^ 2 + (y1 - y2) ^ 2
 
 const Cursor = ({ mouse: point, color }) => {
     if (!point) return
@@ -76,7 +80,7 @@ const Cursor = ({ mouse: point, color }) => {
     const onPointMove = usePerfectCursor(animate)
     useLayoutEffect(() => onPointMove(point), [point, onPointMove])
 
-    color = color ?? "#eeeeee"
+    color = color ?? DEFAULT_CURSOR_COLOR
 
     return html`
     <div
@@ -88,8 +92,10 @@ const Cursor = ({ mouse: point, color }) => {
         width: 20,
         height: 20,
         borderRadius: 10,
-        border: "solid 8px " + hexToRGBA(color , 0.5 ),
+        border: "solid 4px " + hexToRGBA(color , 0.5),
         backgroundColor: color,
+        "-webkit-background-clip": "padding-box", /* for Safari */
+        backgroundClip: "padding-box", /* for IE9+, Firefox 4+, Opera, Chrome */
       }}
     ></div>
     `
@@ -113,10 +119,13 @@ export const MultiplayerPanel = ({ users, client_id }) => {
         })
     }, CURSOR_THROTTLE_RATE), [client_id])
 
-    // usePassiveDocumentEventListener("blur", update_notebook(notebook => {
-    //     if (!(client_id in notebook.users)) return
-    //     notebook.users[client_id].mouse = null
-    // }), [])
+
+    const hide_mouse_for_client = useCallback(() => update_notebook(notebook => {
+        if (!(client_id in notebook.users)) return
+        notebook.users[client_id].mouse = null
+    }), [client_id])
+
+    usePassiveDocumentEventListener("blur", hide_mouse_for_client, [hide_mouse_for_client])
 
     return html`
         <div className="pluto-multiplayer">