diff --git a/README.md b/README.md
index 92aba36..b98af8f 100644
--- a/README.md
+++ b/README.md
@@ -3,3 +3,20 @@
 DrugWars (DopeWars) clone for the [Arduboy](https://www.arduboy.com).
 
 [Reference implementation.](https://gist.github.com/mattmanning/1002653/b7a1e88479a10eaae3bd5298b8b2c86e16fb4404)
+
+## Building
+
+Run `make` to build `slangin.hex`. You need [arduino-cli](https://github.com/arduino/arduino-cli) on your path already set up to compile for the Arduboy.
+
+## Running
+
+Run `make run` to build and run the game. You need the [sim-arduboy](https://github.com/dxxb/sim-arduboy) emulator on your path.
+
+To run on an actual device, use `arduino-cli` to upload `slangin.hex` after building. For example:
+
+```
+make && \
+arduino-cli upload -b arduino:avr:leonardo -p /dev/ttyACM1 slangin.hex
+```
+
+Your port path (`-p` argument) may differ depending on your system.