README updated.

README.md

@@ -1,2 +1,13 @@
-Asteroid game for the [Flipper Zero](https://flipperzero.one/).
-This is a work in progress. Repository created only to push as backup.
+This is an implementation of the classic Asteroids game for the [Flipper Zero](https://flipperzero.one/). Inside you will find a simple 2D engine that can be reused to implement other games.
+
+Controls:
+* Left/Right: rotate ship in the two directions.
+* Ok, short press: fire bullets.
+* Ok, long press: accelerate towards ship head.
+* Down: decelerates.
+
+This is a screenshot, but the game looks a lot better in the device itself:
+
+![Asteroids for Flipper Zero screenshot](/images/Asteroids.jpg)
+
+Don't miss the game over screen. BSD licensed. Enjoy.