diff --git a/playground/4-callbacks.js b/playground/4-callbacks.js
new file mode 100644
index 0000000..cf643df
--- /dev/null
+++ b/playground/4-callbacks.js
@@ -0,0 +1,33 @@
+// setTimeout(() => {
+//   console.log('Two seconds are up')
+// }, 2000)
+//
+// const names = ['Jason', 'Jen', 'Jess']
+// const shortNames = names.filter((name) => {
+//   return name.length <= 4
+// })
+//
+// const geocode = (address, callback) => {
+//   setTimeout(() => {
+//     const data = {
+//       latitude: 0,
+//       longitude: 0
+//     }
+//
+//     callback(data)
+//   }, 2000)
+// }
+//
+// geocode('Philadelphia', (data) => {
+//   console.log(data)
+// })
+
+const add = (x, y, callback) => {
+  setTimeout(() => {
+    callback(x + y)
+  }, 2000)
+}
+
+add(1, 4, (sum) => {
+    console.log(sum) // Should print: 5
+})