Buttons visual feedback

app/src/main/res/drawable/button_background_released.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android">
+    <stroke
+        android:width="2dp"
+        android:color="@color/accent" />
+    <corners android:radius="15dp" />
+    <padding
+        android:bottom="5dp"
+        android:left="5dp"
+        android:right="5dp"
+        android:top="5dp" />
+</shape>