Merge pull request 'add gamble' (#72) from feature/add-gamble into develop

Reviewed-on: #72
Reviewed-by: Pham Huynh Duc Huy <huy.pham@mercurystudiogroup.com>

docs/03-setup-special-feature/02-gamble.md

@@ -4,4 +4,20 @@ sidebar_position: 2
 
 # Gamble
 
-> To be added
+## Overview
+
+![Gamble Preview](./img/gamble/gamble-preview.png)
+
+---
+
+## Implementation
+
+Only need to set up the background in the **main scene**.
+
+#### Landscape
+
+![Gamble Background - Landscape](./img/gamble/gamble-bg-landscape.png)
+
+#### Portrait
+
+![Gamble Background - Portrait](./img/gamble/gamble-bg-portrait.png)