diff --git a/2016/input/day_12.txt b/2016/input/day_12.txt
new file mode 100644
index 0000000..8084c18
--- /dev/null
+++ b/2016/input/day_12.txt
@@ -0,0 +1,23 @@
+cpy 1 a
+cpy 1 b
+cpy 26 d
+jnz c 2
+jnz 1 5
+cpy 7 c
+inc d
+dec c
+jnz c -2
+cpy a c
+inc a
+dec b
+jnz b -2
+cpy c b
+dec d
+jnz d -6
+cpy 16 c
+cpy 17 d
+inc a
+dec d
+jnz d -2
+dec c
+jnz c -5
\ No newline at end of file
diff --git a/2016/rust/src/day_12.rs b/2016/rust/src/day_12.rs
new file mode 100644
index 0000000..b7827c8
--- /dev/null
+++ b/2016/rust/src/day_12.rs
@@ -0,0 +1,98 @@
+use std::collections::HashMap;
+
+use errors::*;
+
+pub fn solve(input: &str) -> Result<String> {
+    Ok("".into())
+}
+
+// The assembunny code you've extracted operates on four registers (a, b, c, and d) that start at 0
+// and can hold any integer. However, it seems to make use of only a few instructions:
+#[derive(Clone, Debug, Hash, Eq, PartialEq)]
+enum Register {
+    A,
+    B,
+    C,
+    D,
+}
+
+enum Variable {
+    Register(Register),
+    Value(usize),
+}
+
+#[derive(Debug, PartialEq)]
+struct State {
+    pc: usize,
+    registers: HashMap<Register, isize>,
+}
+
+impl State {
+    fn value(&self, v: &Variable) -> isize {
+        match v {
+            &Variable::Register(ref r) => {
+                self.registers.get(r).cloned().unwrap_or(0 as isize)
+            }
+            &Variable::Value(value) => value as isize,
+        }
+    }
+}
+
+// cpy x y copies x (either an integer or the value of a register) into register y.
+struct Copy {
+    variable: Variable,
+    register: Register,
+}
+
+impl Copy {
+    fn run(&self, state: &State) -> State {
+        let pc = state.pc + 1;
+        let value = state.value(&self.variable);
+        let mut registers = state.registers.clone();
+        registers.insert(self.register.clone(), value);
+        State {
+            pc: pc,
+            registers: registers,
+        }
+    }
+}
+
+// inc x increases the value of register x by one.
+// dec x decreases the value of register x by one.
+// jnz x y jumps to an instruction y away (positive means forward; negative means backward), but only if x is not zero.
+
+#[cfg(test)]
+mod tests {
+    use super::{Variable, Register, State, Copy};
+
+    #[test]
+    fn test_state_value() {
+        let state = State {
+            pc: 0,
+            registers: vec![(Register::A, 41)].into_iter().collect(),
+        };
+        assert_eq!(state.value(&Variable::Register(Register::A)), 41);
+        assert_eq!(state.value(&Variable::Register(Register::B)), 0);
+        assert_eq!(state.value(&Variable::Value(23)), 23);
+    }
+
+    #[test]
+    fn test_copy() {
+        let variable = Variable::Value(41);
+        let register = Register::A;
+        let copy = Copy {
+            variable: variable,
+            register: register,
+        };
+        let state = State {
+            pc: 0,
+            registers: vec![].into_iter().collect(),
+        };
+        let expected = State {
+            pc: 1,
+            registers: vec![(Register::A, 41)].into_iter().collect(),
+        };
+
+        assert_eq!(copy.run(&state), expected);
+    }
+}
diff --git a/2016/rust/src/lib.rs b/2016/rust/src/lib.rs
index ba7f4b3..8963715 100644
--- a/2016/rust/src/lib.rs
+++ b/2016/rust/src/lib.rs
@@ -1,4 +1,4 @@
-#![feature(inclusive_range_syntax)]
+#![feature(field_init_shorthand, inclusive_range_syntax)]
 #![recursion_limit = "1024"]
 
 #[macro_use]
@@ -15,5 +15,6 @@ pub mod day_05;
 pub mod day_06;
 pub mod day_07;
 pub mod day_08;
-pub mod day_09;
+// pub mod day_09;
 // pub mod day_10;
+pub mod day_12;
diff --git a/2016/rust/src/main.rs b/2016/rust/src/main.rs
index b7f73a8..27be66b 100644
--- a/2016/rust/src/main.rs
+++ b/2016/rust/src/main.rs
@@ -10,7 +10,7 @@ fn main() {
     let mut input = String::new();
     io::stdin().read_to_string(&mut input).ok();
 
-    let solution = day_09::solve(&input)?;
+    let solution = day_12::solve(&input)?;
     println!("{}", solution);
 
     Ok(())