add README

Makefile

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 main: *.c
-	vamos -c ../.vamosc sc main.c LINK
+	vamos -c ../.vamosrc sc main.c LINK

README.md

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+# Pizza Timer
+
+This is the pizza timer written in C for the Commodore Amiga I made for
+"Can a Commodore Amiga help you cook a pizza?" on YouTube: https://youtu.be/QrrugOgFmjg
+
+## Requirements
+
+* AmigaOS 2 and higher
+  * I use the GadTools library to build the timer, which only works out-od-the-box
+    on 2 and higher.
+  * The timer can take advantage of AmigaOS 3 updates to GadTools for displaying
+    the timer text.
+
+## Running
+
+* `main` and `bell.8svx` will run the timer itself
+  * You'll need `bell.8svx` in the same folder as `main` if you want to
+    hear the bell noise.
+* `justwindow` will show the basic window with no gadgets besides window ones.
+
+## Compiling
+
+I built this using [vamos](https://lallafa.de/blog/amiga-projects/amitools/vamos/)
+and SAS/C on my Linux machine, which I set up using
+[this guide](https://lallafa.de/blog/2011/12/running-the-amiga-sas-c-6-58-compiler-with-vamos/).
+Having GNU make installed makes the process a little easier.
+
+## Credits
+
+* "Reception bell" by cdrk
+  * https://freesound.org/people/cdrk/sounds/264594/
+  * CC-BY 4.0
+