Update README.md

Author: snesrev

Diff for: README.md

@@ -1,8 +1,19 @@
 # smw
+A reimplementation of Super Mario World.
 
 Our discord server is: https://discord.gg/AJJbJAzNNJ
 
-Early version. It has bugs and the code is messy.
+## About
+
+This is a reverse engineered clone of Super Mario World.
+
+It reimplements all parts of the original game and a bunch of mods added by Lunar Magic. The game is playable from start to end.
+
+You need a copy of the ROM to extract game resources (levels, images). Then once that's done, the ROM is no longer needed.
+
+It uses the PPU and DSP implementation from [LakeSnes](https://github.com/elzo-d/LakeSnes), but with lots of speed optimizations.
+
+## Building
 
 You must self-build for now. Easy method on 64-bit Windows (no terminal or big downloads):<br>
 (1) Download [Python](https://www.python.org/ftp/python/3.11.4/python-3.11.4-amd64.exe) if you don't have it and install with "Add to PATH" checked<br>
@@ -17,3 +28,42 @@ For other platforms and compilers, see: https://github.com/snesrev/smw/blob/main
 
 When running, it runs an emulated version in the background and compares the ram state every frame. If it detects a mismatch, it saves a snapshot in saves/ and displays a counter on screen counting down from 300. Please submit these bug snapshots on discord so that they can be fixed.
 
+## Usage and controls
+
+The game supports snapshots. The joypad input history is also saved in the snapshot. It's thus possible to replay a playthrough in turbo mode to verify that the game behaves correctly.
+
+| Button | Key         |
+| ------ | ----------- |
+| Up     | Up arrow    |
+| Down   | Down arrow  |
+| Left   | Left arrow  |
+| Right  | Right arrow |
+| Start  | Enter       |
+| Select | Right shift |
+| A      | X           |
+| B      | Z           |
+| X      | S           |
+| Y      | A           |
+| L      | C           |
+| R      | V           |
+
+The keys can be reconfigured in smw.ini
+
+Additionally, the following commands are available:
+
+| Key | Action                |
+| --- | --------------------- |
+| Tab | Turbo mode |
+| P   | Pause (with dim)                |
+| Shift+P   | Pause (without dim)                |
+| Ctrl+Up   | Increase window size                |
+| Ctrl+Down   | Decrease window size                |
+| T   | Toggle replay turbo mode  |
+| K   | Clear all input history from the joypad log  |
+| L   | Stop replaying a shapshot  |
+| R   | Toggle between fast and slow renderer |
+| F   | Display renderer performance |
+| F1-F10 | Load snapshot      |
+| Alt+Enter | Toggle Fullscreen     |
+| Shift+F1-F10 | Save snapshot |
+| Ctrl+F1-F10 | Replay the snapshot |