diff --git a/prototype/src/App.tsx b/prototype/src/App.tsx
index 0223f28..ff0dfaa 100644
--- a/prototype/src/App.tsx
+++ b/prototype/src/App.tsx
@@ -141,7 +141,7 @@ export default function App(): JSX.Element {
               />
               {ob.moving && (
                 <text x={sx(ob.pos.x)} y={sy(ob.pos.y) + 4} style={styles.obLabel as never}>
-                  mobile
+                  transit
                 </text>
               )}
             </g>
@@ -186,7 +186,7 @@ export default function App(): JSX.Element {
             <div style={styles.dim}>blue line — pose broadcast (5 Hz, ~46 B)</div>
             <div style={styles.dim}>green line — bulk sync (sealed partitions)</div>
             <div style={styles.dim}>flash — broadcast event delivered</div>
-            <div style={styles.dim}>red circle — mobile obstacle</div>
+            <div style={styles.dim}>red circle — transit object crossing the area</div>
           </Section>
         </aside>
       </div>
diff --git a/prototype/src/sim.ts b/prototype/src/sim.ts
index 287b94a..f57f815 100644
--- a/prototype/src/sim.ts
+++ b/prototype/src/sim.ts
@@ -65,12 +65,52 @@ function rnd(): number {
   return ((seedState >>> 0) % 100000) / 100000;
 }
 
-const WAYPOINTS: Vec[] = [
+// Two interleaved patrol routes: even drones circle the perimeter, odd
+// drones fly an X through the center. Paths cross mid-field, so the mesh
+// keeps bridging between the front and the back of the formation instead
+// of stretching into disconnected segments along one loop.
+const PERIMETER: Vec[] = [
   { x: 120, y: 120 },
   { x: AREA - 120, y: 150 },
   { x: AREA - 150, y: AREA - 120 },
   { x: 150, y: AREA - 150 },
 ];
+const CROSS: Vec[] = [
+  { x: 150, y: 150 },
+  { x: AREA - 150, y: AREA - 150 },
+  { x: AREA - 150, y: 150 },
+  { x: 150, y: AREA - 150 },
+];
+function routeOf(d: Drone): Vec[] {
+  return d.id % 2 === 0 ? PERIMETER : CROSS;
+}
+
+// Transit objects enter at one edge, cross the whole area, and respawn at
+// a fresh edge once they leave — a stream of through-traffic instead of
+// obstacles bouncing until they wedge into a corner.
+const TRANSIT_MARGIN = 120;
+function spawnTransit(id: number): Obstacle {
+  const speed = 26 + rnd() * 30;
+  const along = 120 + rnd() * (AREA - 240);
+  const skew = (rnd() - 0.5) * speed * 0.9; // diagonal-ish crossings
+  const edge = Math.floor(rnd() * 4);
+  const table: { pos: Vec; vel: Vec }[] = [
+    { pos: { x: along, y: -TRANSIT_MARGIN + 20 }, vel: { x: skew, y: speed } },
+    { pos: { x: along, y: AREA + TRANSIT_MARGIN - 20 }, vel: { x: skew, y: -speed } },
+    { pos: { x: -TRANSIT_MARGIN + 20, y: along }, vel: { x: speed, y: skew } },
+    { pos: { x: AREA + TRANSIT_MARGIN - 20, y: along }, vel: { x: -speed, y: skew } },
+  ];
+  const { pos, vel } = table[edge];
+  return { id, pos, radius: 22 + rnd() * 16, moving: true, vel };
+}
+function outOfTransit(ob: Obstacle): boolean {
+  return (
+    ob.pos.x < -TRANSIT_MARGIN ||
+    ob.pos.x > AREA + TRANSIT_MARGIN ||
+    ob.pos.y < -TRANSIT_MARGIN ||
+    ob.pos.y > AREA + TRANSIT_MARGIN
+  );
+}
 
 export function makeWorld(droneCount: number): World {
   const drones: Drone[] = Array.from({ length: droneCount }, (_, i) => {
@@ -83,7 +123,7 @@ export function makeWorld(droneCount: number): World {
       },
       vel: { x: 0, y: 0 },
       heading: angle,
-      waypoint: i % WAYPOINTS.length,
+      waypoint: i % PERIMETER.length,
       battery: 90 + rnd() * 10,
       channel: CHANNELS[i % CHANNELS.length],
     };
@@ -92,8 +132,9 @@ export function makeWorld(droneCount: number): World {
     { id: 0, pos: { x: 340, y: 420 }, radius: 60, moving: false, vel: { x: 0, y: 0 } },
     { id: 1, pos: { x: 700, y: 260 }, radius: 45, moving: false, vel: { x: 0, y: 0 } },
     { id: 2, pos: { x: 560, y: 720 }, radius: 70, moving: false, vel: { x: 0, y: 0 } },
-    { id: 3, pos: { x: 200, y: 800 }, radius: 30, moving: true, vel: { x: 14, y: -6 } },
-    { id: 4, pos: { x: 820, y: 620 }, radius: 26, moving: true, vel: { x: -10, y: 9 } },
+    spawnTransit(3),
+    spawnTransit(4),
+    spawnTransit(5),
   ];
   return { t: 0, drones, obstacles, links: new Map(), totalBytes: 0, broadcasts: 0 };
 }
@@ -103,12 +144,13 @@ function linkKey(a: number, b: number): string {
 }
 
 function steer(d: Drone, world: World, dt: number): Drone {
-  const wp = WAYPOINTS[(d.waypoint + d.id) % WAYPOINTS.length];
+  const route = routeOf(d);
+  const wp = route[(d.waypoint + d.id) % route.length];
   let ax = wp.x - d.pos.x;
   let ay = wp.y - d.pos.y;
   const wpDist = Math.hypot(ax, ay);
   let waypoint = d.waypoint;
-  if (wpDist < 90) waypoint = (d.waypoint + 1) % WAYPOINTS.length;
+  if (wpDist < 90) waypoint = (d.waypoint + 1) % route.length;
   ax /= wpDist || 1;
   ay /= wpDist || 1;
 
@@ -157,18 +199,15 @@ function steer(d: Drone, world: World, dt: number): Drone {
 
 export function tick(world: World, dt: number): World {
   const drones = world.drones.map((d) => steer(d, world, dt));
-  const obstacles = world.obstacles.map((ob) =>
-    ob.moving
-      ? {
-          ...ob,
-          pos: { x: ob.pos.x + ob.vel.x * dt, y: ob.pos.y + ob.vel.y * dt },
-          vel: {
-            x: ob.pos.x < 60 || ob.pos.x > AREA - 60 ? -ob.vel.x : ob.vel.x,
-            y: ob.pos.y < 60 || ob.pos.y > AREA - 60 ? -ob.vel.y : ob.vel.y,
-          },
-        }
-      : ob,
-  );
+  const obstacles = world.obstacles.map((ob) => {
+    if (!ob.moving) return ob;
+    const moved = {
+      ...ob,
+      pos: { x: ob.pos.x + ob.vel.x * dt, y: ob.pos.y + ob.vel.y * dt },
+    };
+    // Once a transit object leaves the area, respawn it at a random edge
+    return outOfTransit(moved) ? spawnTransit(ob.id) : moved;
+  });
 
   const links = new Map(world.links);
   let totalBytes = world.totalBytes;