===================================================================
--- original.js
+++ change.js
@@ -88,11 +88,14 @@
 			obstacles[i].destroy();
 			obstacles.splice(i, 1);
 		}
 	}
-	// Spawn obstacles
-	if (LK.ticks % 120 === 0) {
-		// Every 2 seconds
+	// Spawn obstacles with variable rate
+	var spawnRate = 120 - Math.floor(LK.ticks / 1800); // Decrease spawn rate every 30 seconds
+	if (spawnRate < 30) {
+		spawnRate = 30;
+	} // Set a minimum spawn rate
+	if (LK.ticks % spawnRate === 0) {
 		var obstacle = new Obstacle();
 		obstacle.x = game.width;
 		obstacle.y = game.height - obstacle.height;
 		obstacles.push(obstacle);