what done?

particlelab/src/main/res/drawable/tool_slot_background.xml

@@ -0,0 +1,15 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android"
+    android:shape="rectangle">
+    <corners android:radius="3dp" />
+    <solid
+        android:color="#715f5f"/>
+    <padding
+        android:bottom="2dp"
+        android:left="2dp"
+        android:right="2dp"
+        android:top="2dp" />
+    <stroke
+        android:width="2dp"
+        android:color="#635e5e" />
+</shape>