diff --git a/.gitignore b/.gitignore
index 6315628..23f45e2 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,4 @@
 !uninstall.sh
 !util.sh
 !.gitignore
+!README.md
diff --git a/README.md b/README.md
new file mode 100644
index 0000000..b71d0bc
--- /dev/null
+++ b/README.md
@@ -0,0 +1,13 @@
+# Automatic `sh-elf-gcc` installer
+
+This script can be used to automatically compile and install a GCC cross-compiler targeting SH3 and SH4 calculators. The normal use is with GiteaPC:
+
+```
+% giteapc install Lephenixnoir/sh-elf-gcc
+```
+
+You can also install manually. First install [`sh-elf-binutils`](https://gitea.planet-casio.com/Lephenixnoir/sh-elf-binutils), then run the GiteaPC Makefile with a manually-specified install prefix:
+
+```
+% make -f giteapc.make configure build install PREFIX=$HOME/.local
+```
diff --git a/giteapc.make b/giteapc.make
index b78c23a..1e46d34 100644
--- a/giteapc.make
+++ b/giteapc.make
@@ -1,7 +1,8 @@
 # giteapc: version=1
 # giteapc: depends=Lephenixnoir/sh-elf-binutils
 
-VERSION=10.2.0
+PREFIX ?= $(GITEAPC_PREFIX)
+VERSION = 10.2.0
 
 configure:
 	@ ./configure.sh $(VERSION)
@@ -10,9 +11,9 @@ build:
 	@ ./build.sh
 
 install:
-	@ ./install.sh "$(GITEAPC_PREFIX)"
+	@ ./install.sh "$(PREFIX)"
 
 uninstall:
-	@ ./uninstall.sh "$(GITEAPC_PREFIX)"
+	@ ./uninstall.sh "$(PREFIX)"
 
 .PHONY: configure build install uninstall