diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 0000000..fb2b2f1
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,28 @@
+name: CI
+on:
+  - push
+  - pull_request
+jobs:
+  build:
+    name: Rust clippy and unit tests
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        rustup_channel:
+          - stable
+          - beta
+          - nightly
+        dev_flag:
+          - ""
+          - "--release"
+    steps:
+      - uses: actions/checkout@v2
+      - name: rustup install
+        run: |
+          rustup toolchain update --no-self-update ${{ matrix.rustup_channel }}
+          rustup default ${{ matrix.rustup_channel }}
+      - name: install just
+        run: cargo install just
+      - run: just build
+      - name: unit tests
+        run: just test
diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/README.md b/README.md
index 500f3c2..060d57c 100644
--- a/README.md
+++ b/README.md
@@ -1,13 +1,16 @@
+// <!--
+riir_macro::print_literally! {
+// -->
 # RIIR
 why not Rewrite It In Rust (**RIIR**)
 
 Are you an author or contributor to a software project?
 
-Have you ever been asked to rewrite, or consider rewriting that project in [Rust](https://www.rust-lang.org/)?
+Have you ever been asked to rewrite, or consider rewriting that project in [Rust][rust-lang]?
 
 If so, you may have been a victim of the RIIR agenda that is sweeping the web.
 
-If this has happened to you, please [report it](https://github.com/ansuz/RIIR/issues/) so that something can be done.
+If this has happened to you, please [report it][issues] so that something can be done.
 
 
 ## FAQ
@@ -18,7 +21,23 @@ No. This is a joke.
 
 ### Y U HATE RUST SO MUCH?
 
-I don't, actually. I believe that those who spend their time asking people to rewrite their projects are probably not themselves active Rust developers, as those active devs are probably busy [writing memory-safe code](https://trac.torproject.org/projects/tor/ticket/11331).
+I don't, actually. I believe that those who spend their time asking people to rewrite their projects are probably not themselves active Rust developers, as those active devs are probably busy [writing memory-safe code][memory-safe].
 
 ### R U OFFENDING ME?
 ![](rust.png)
+
+## Building
+This readme is valid Rust language.
+It can be built into an executable by running the [just][just] command:
+
+    just build
+
+Then run "just test", and this readme will be regenerated in Rust code!
+
+[rust-lang]: https://www.rust-lang.org/
+[issues]: https://github.com/ansuz/RIIR/issues/
+[memory-safe]: https://trac.torproject.org/projects/tor/ticket/11331
+[just]: https://github.com/casey/just
+
+// <!--
+} // -->
diff --git a/justfile b/justfile
new file mode 100644
index 0000000..0448e9d
--- /dev/null
+++ b/justfile
@@ -0,0 +1,19 @@
+build: clean build-macro
+	#!/usr/bin/env bash
+	LIB_PATH=$(echo -n target/debug/deps/libriir_macro-*.so)
+	rustc \
+		--crate-name riir \
+		--edition=2018 \
+		README.md \
+		--crate-type bin \
+		--out-dir target/debug \
+		-L dependency=target/debug/deps \
+		--extern riir_macro=$LIB_PATH
+clean:
+	#!/usr/bin/env bash
+	rm target/debug/deps/libriir_macro-*.so || true
+build-macro:
+	cd riir-macro && cargo build --target-dir=../target $( (rustc --version | grep nightly >/dev/null) && echo --features span)
+
+test:
+	cd riir-macro && cargo test --target-dir=../target $( (rustc --version | grep nightly >/dev/null) && echo --features span)
diff --git a/riir-macro/Cargo.lock b/riir-macro/Cargo.lock
new file mode 100644
index 0000000..c7f96f9
--- /dev/null
+++ b/riir-macro/Cargo.lock
@@ -0,0 +1,33 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+[[package]]
+name = "proc-macro2"
+version = "1.0.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "beae6331a816b1f65d04c45b078fd8e6c93e8071771f41b8163255bbd8d7c8fa"
+dependencies = [
+ "unicode-xid",
+]
+
+[[package]]
+name = "quote"
+version = "1.0.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
+dependencies = [
+ "proc-macro2",
+]
+
+[[package]]
+name = "riir-macro"
+version = "0.1.0"
+dependencies = [
+ "proc-macro2",
+ "quote",
+]
+
+[[package]]
+name = "unicode-xid"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
diff --git a/riir-macro/Cargo.toml b/riir-macro/Cargo.toml
new file mode 100644
index 0000000..25ce472
--- /dev/null
+++ b/riir-macro/Cargo.toml
@@ -0,0 +1,14 @@
+[package]
+name = "riir-macro"
+version = "0.1.0"
+edition = "2018"
+
+[lib]
+proc-macro = true
+
+[dependencies]
+proc-macro2 = "1.0.18"
+quote = "1.0.6"
+
+[features]
+span = ["proc-macro2/span-locations"]
diff --git a/riir-macro/src/lib.rs b/riir-macro/src/lib.rs
new file mode 100644
index 0000000..d34d077
--- /dev/null
+++ b/riir-macro/src/lib.rs
@@ -0,0 +1,142 @@
+#![cfg_attr(feature = "span", feature(proc_macro_span))]
+
+use proc_macro2::{Delimiter, Span, TokenStream, TokenTree};
+use quote::quote;
+
+#[proc_macro]
+pub fn print_literally(ts: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let string = print_ts(ts.into());
+    let ts = quote! {
+        fn main() {
+            print!(#string);
+        }
+    };
+    ts.into()
+}
+
+fn print_ts(ts: TokenStream) -> String {
+    let mut output = String::new();
+
+    #[cfg_attr(feature = "span", allow(unused_mut, unused_variables))]
+    let mut was_hash = false;
+    #[cfg_attr(not(feature = "span"), allow(unused_mut, unused_variables))]
+    let mut last_span: Option<Span> = None;
+
+    for tt in ts {
+        #[cfg(feature = "span")]
+        {
+            if let Some(last_span) = last_span {
+                let end = last_span.end();
+                let start = tt.span().start();
+                let end_col = if start.line > end.line {
+                    let lines = start.line - end.line;
+                    output.extend((0..lines).map(|_| '\n'));
+                    0
+                } else {
+                    end.column
+                };
+                let space_size = start.column as isize - end_col as isize;
+                output.extend((0..space_size).map(|_| ' '));
+            }
+        }
+        #[cfg_attr(not(feature = "span"), allow(unused_assignments))]
+        {
+            last_span = Some(tt.span());
+        }
+        match tt {
+            TokenTree::Ident(ident) => {
+                #[cfg_attr(not(feature = "span"), allow(unused_mut))]
+                let mut string = ident.to_string();
+                #[cfg(feature = "span")]
+                {
+                    fill_space(ident.span(), &mut string);
+                }
+                #[cfg(not(feature = "span"))]
+                {
+                    string.push(' ');
+                }
+                output.push_str(&string);
+            }
+            TokenTree::Punct(punct) => {
+                let mut string = punct.as_char().to_string();
+                #[cfg(feature = "span")]
+                {
+                    fill_space(punct.span(), &mut string);
+                }
+                #[cfg(not(feature = "span"))]
+                {
+                    use proc_macro2::Spacing;
+
+                    if punct.as_char() == '#' {
+                        if !was_hash {
+                            string = format!("\n{}", string);
+                        }
+                        was_hash = true;
+                    }
+                    if punct.spacing() == Spacing::Joint {
+                        string.push(' ');
+                    }
+                }
+                output.push_str(&string);
+            }
+            TokenTree::Literal(lit) => {
+                #[cfg_attr(not(feature = "span"), allow(unused_mut))]
+                let mut string = lit.to_string();
+                #[cfg(feature = "span")]
+                {
+                    fill_space(lit.span(), &mut string);
+                }
+                output.push_str(&string);
+            }
+            TokenTree::Group(group) => {
+                let mut string = String::new();
+                let (l, r) = match group.delimiter() {
+                    Delimiter::Parenthesis => ("(", ")"),
+                    Delimiter::Bracket => ("[", "]"),
+                    Delimiter::Brace => ("{", "}"),
+                    Delimiter::None => ("", ""),
+                };
+                string.push_str(l);
+                string.push_str(&print_ts(group.stream()));
+                string.push_str(r);
+                #[cfg(feature = "span")]
+                {
+                    fill_space(group.span(), &mut string);
+                }
+                output.push_str(&string);
+            }
+        }
+    }
+    output
+}
+
+#[cfg(feature = "span")]
+fn fill_space(span: Span, string: &mut String) {
+    let start_col = if span.end().line > span.start().line {
+        let lines = span.end().line - span.start().line;
+        string.extend((0..lines).map(|_| '\n'));
+        -1
+    } else {
+        (span.start().column + string.len()) as isize
+    };
+    let space_size = span.end().column as isize - start_col;
+    string.extend((0..space_size).map(|_| ' '));
+}
+
+#[cfg(test)]
+#[test]
+fn test() {
+    use std::{fs, path::PathBuf};
+
+    let path = PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("test.txt");
+    let content = fs::read_to_string(path).unwrap();
+    let actual = print_ts(content.parse().unwrap());
+    #[cfg(feature = "span")]
+    {
+        assert_eq!(actual, content.trim());
+    }
+    #[cfg(not(feature = "span"))]
+    {
+        // TODO write unit tests for non-span-sensitive code
+    }
+}
diff --git a/riir-macro/test.txt b/riir-macro/test.txt
new file mode 100644
index 0000000..40edba1
--- /dev/null
+++ b/riir-macro/test.txt
@@ -0,0 +1,2 @@
+a bc
+  ## de  f
diff --git a/rust-toolchain b/rust-toolchain
new file mode 100644
index 0000000..bf867e0
--- /dev/null
+++ b/rust-toolchain
@@ -0,0 +1 @@
+nightly