diff --git a/Cargo.lock b/Cargo.lock
index 6d9bf1c..55ffcc1 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -12,6 +12,20 @@ version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
 
+[[package]]
+name = "dice-stats"
+version = "0.1.0"
+dependencies = [
+ "itertools",
+ "rand",
+]
+
+[[package]]
+name = "either"
+version = "1.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fcaabb2fef8c910e7f4c7ce9f67a1283a1715879a7c230ca9d6d1ae31f16d91"
+
 [[package]]
 name = "fraction-math"
 version = "0.1.0"
@@ -27,12 +41,25 @@ dependencies = [
  "wasi",
 ]
 
+[[package]]
+name = "itertools"
+version = "0.10.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b0fd2260e829bddf4cb6ea802289de2f86d6a7a690192fbe91b3f46e0f2c8473"
+dependencies = [
+ "either",
+]
+
 [[package]]
 name = "libc"
 version = "0.2.139"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "201de327520df007757c1f0adce6e827fe8562fbc28bfd9c15571c66ca1f5f79"
 
+[[package]]
+name = "parens"
+version = "0.1.0"
+
 [[package]]
 name = "ppv-lite86"
 version = "0.2.17"
diff --git a/Cargo.toml b/Cargo.toml
index 0f09fb6..4e495e2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,7 +1,9 @@
 [workspace]
 members = [
   "balance",
+  "dice-stats",
   "fraction-math",
+  "parens",
   "repeated-groups",
   "scramble"
 ]
diff --git a/parens/Cargo.toml b/parens/Cargo.toml
new file mode 100644
index 0000000..baf37e9
--- /dev/null
+++ b/parens/Cargo.toml
@@ -0,0 +1,8 @@
+[package]
+name = "parens"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
diff --git a/parens/src/main.rs b/parens/src/main.rs
new file mode 100644
index 0000000..3407f4d
--- /dev/null
+++ b/parens/src/main.rs
@@ -0,0 +1,52 @@
+use std::env::args;
+
+fn main() {
+    let mut args = args();
+
+    // Consume the first arg, it's the executable name, we don't care in this
+    // context.
+    let _ = args.next();
+
+    match args.next() {
+        Some(parens) => match to_balance(parens) {
+            Ok(balance) => println!("{}", balance),
+            Err(e) => eprintln!("{}", e),
+        },
+        None => println!("Nothing to do. Exiting..."),
+    }
+}
+
+fn to_balance(input: String) -> Result<isize, String> {
+    let mut diff = 0;
+    for c in input.chars() {
+        match c {
+            '(' => diff += 1,
+            ')' => diff -= 1,
+            c => return Err(format!("unexpected character {}", c)),
+        }
+    }
+    Ok(diff)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn balance_parens() {
+        let cases: Vec<(String, Result<isize, String>)> = vec![
+            ("()".to_string(), Ok(0)),
+            ("(()".to_string(), Ok(1)),
+            ("))()))))()".to_string(), Ok(-6)),
+            (")))))".to_string(), Ok(-5)),
+            (
+                "foobar".to_string(),
+                Err("unexpected character f".to_string()),
+            ),
+        ];
+
+        for c in cases {
+            assert_eq!(c.1, to_balance(c.0));
+        }
+    }
+}