diff --git a/src/lib.rs b/src/lib.rs
index b42088e..1f641d1 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,6 +1,7 @@
 pub mod memory;
 pub mod stack;
 
+use std::cell::{Cell, RefCell, RefMut};
 use std::rc::Rc;
 use std::*;
 
@@ -73,8 +74,10 @@ impl Device for SystemDevice {
     fn deo1(&mut self, vm: &mut Uxn, port: u8, val: u8) {
         let slot = port & 0xF;
         match slot {
-            0x2 => vm.wst.idx = val,
-            0x3 => vm.rst.idx = val,
+            // Note: This VM does not support mutating the stack pointers.
+            // This operation is not well defined upstream
+            0x2 => panic!("Invoked unsupported mutation of the data stack pointer"),
+            0x3 => panic!("Invoked unsupported mutation of the return stack pointer"),
             x => self.buffer[x as usize] = val,
         }
     }
@@ -95,9 +98,9 @@ impl Device for SystemDevice {
 
 #[derive(Debug)]
 pub struct Uxn {
-    memory: Box<TrivialMemory>,
+    memory: Rc<RefCell<TrivialMemory>>,
     // Note: Using Rc so we can start with many NullDevs and replace them
-    devices: [Box<dyn Device>; 16],
+    devices: [Rc<RefCell<dyn Device>>; 16],
     pc: u16,    // Program counter
     wst: Stack, // Data stack
     rst: Stack, // Return stack pointer
@@ -106,24 +109,24 @@ pub struct Uxn {
 impl Uxn {
     pub fn new() -> Uxn {
         Uxn {
-            memory: Box::new(TrivialMemory::new()),
+            memory: Rc::new(RefCell::new(TrivialMemory::new())),
             devices: [
-                Box::new(SystemDevice::new()), // #00
-                Box::new(NullDevice::new()),   // #01
-                Box::new(NullDevice::new()),   // #02
-                Box::new(NullDevice::new()),   // #03
-                Box::new(NullDevice::new()),   // #04
-                Box::new(NullDevice::new()),   // #05
-                Box::new(NullDevice::new()),   // #06
-                Box::new(NullDevice::new()),   // #07
-                Box::new(NullDevice::new()),   // #08
-                Box::new(NullDevice::new()),   // #09
-                Box::new(NullDevice::new()),   // #0a
-                Box::new(NullDevice::new()),   // #0b
-                Box::new(NullDevice::new()),   // #0c
-                Box::new(NullDevice::new()),   // #0d
-                Box::new(NullDevice::new()),   // #0e
-                Box::new(NullDevice::new()),   // #0f
+                Rc::new(RefCell::new(SystemDevice::new())), // #00
+                Rc::new(RefCell::new(NullDevice::new())),   // #01
+                Rc::new(RefCell::new(NullDevice::new())),   // #02
+                Rc::new(RefCell::new(NullDevice::new())),   // #03
+                Rc::new(RefCell::new(NullDevice::new())),   // #04
+                Rc::new(RefCell::new(NullDevice::new())),   // #05
+                Rc::new(RefCell::new(NullDevice::new())),   // #06
+                Rc::new(RefCell::new(NullDevice::new())),   // #07
+                Rc::new(RefCell::new(NullDevice::new())),   // #08
+                Rc::new(RefCell::new(NullDevice::new())),   // #09
+                Rc::new(RefCell::new(NullDevice::new())),   // #0a
+                Rc::new(RefCell::new(NullDevice::new())),   // #0b
+                Rc::new(RefCell::new(NullDevice::new())),   // #0c
+                Rc::new(RefCell::new(NullDevice::new())),   // #0d
+                Rc::new(RefCell::new(NullDevice::new())),   // #0e
+                Rc::new(RefCell::new(NullDevice::new())),   // #0f
             ],
             pc: 0x0100,
             wst: Stack::new(),
@@ -132,27 +135,26 @@ impl Uxn {
     }
 
     pub fn is_halted(&mut self) -> bool {
-        let dev = self.devices[0].as_mut();
-        dev.dei1(self, 0x0f) != 0
+        self.dei1(0x0f) != 0
+    }
+
+    fn device(&self, port: u8) -> Rc<RefCell<dyn Device>> {
+        Rc::clone(&self.devices[(port & 0xF0 >> 4) as usize])
     }
 
     pub fn dei1(&mut self, port: u8) -> u8 {
-        let dev = self.devices[(port & 0xF0 >> 4) as usize];
-        dev.dei1(self, port)
+        self.device(port).borrow_mut().dei1(self, port)
     }
 
     pub fn dei2(&mut self, port: u8) -> u16 {
-        let dev = self.devices[(port & 0xF0 >> 4) as usize];
-        dev.dei2(self, port)
+        self.device(port).borrow_mut().dei2(self, port)
     }
 
     pub fn deo1(&mut self, port: u8, val: u8) {
-        let dev = self.devices[(port & 0xF0 >> 4) as usize].as_mut();
-        dev.deo1(self, port, val)
+        self.device(port).borrow_mut().deo1(self, port, val);
     }
 
     pub fn deo2(&mut self, port: u8, val: u16) {
-        let dev = self.devices[(port & 0xF0 >> 4) as usize].as_mut();
-        dev.deo2(self, port, val)
+        self.device(port).borrow_mut().deo2(self, port, val);
     }
 }
diff --git a/src/stack.rs b/src/stack.rs
index f496201..d3bfe37 100644
--- a/src/stack.rs
+++ b/src/stack.rs
@@ -39,20 +39,55 @@ impl Stack {
         }
     }
 
-    pub fn pop1(&mut self) -> Result<u8, StackError> {
+    pub fn get1(&self, idx: u8) -> Result<u8, StackError> {
+        Ok(self.buff[idx as usize])
+    }
+
+    pub fn peek1(&self) -> Result<u8, StackError> {
         if self.idx == 0 {
             Err(StackError::StackUnderflow)
         } else {
-            self.idx -= 1;
-            Ok(self.buff[self.idx as usize])
+            Ok(self.get1(self.idx - 1)?)
+        }
+    }
+
+    pub fn pop1(&mut self) -> Result<u8, StackError> {
+        let val = self.peek1()?;
+        self.idx -= 1;
+        Ok(val)
+    }
+
+    pub fn get2(&self, idx: u8) -> Result<u16, StackError> {
+        if idx == 255 {
+            Err(StackError::StackOverflow)
+        } else {
+            let high = self.buff[idx as usize] as u16;
+            let low = self.buff[(idx + 1) as usize] as u16;
+            Ok((high << 8) + low)
+        }
+    }
+
+    pub fn peek2(&mut self) -> Result<u16, StackError> {
+        if self.idx < 2 {
+            Err(StackError::StackUnderflow)
+        } else {
+            self.get2(self.idx - 2)
         }
     }
 
     pub fn pop2(&mut self) -> Result<u16, StackError> {
-        if self.idx < 2 {
-            Err(StackError::StackUnderflow)
-        } else {
-            Ok(((self.pop1()? as u16) << 8) + self.pop1()? as u16)
-        }
+        let val = self.peek2()?;
+        self.idx -= 2;
+        Ok(val)
+    }
+
+    pub fn move1(&mut self, other: &mut Stack) -> Result<(), StackError> {
+        other.push1(self.pop1()?)?;
+        Ok(())
+    }
+
+    pub fn move2(&mut self, other: &mut Stack) -> Result<(), StackError> {
+        other.push2(self.pop2()?)?;
+        Ok(())
     }
 }