diff --git a/assets/test_prelude.ld b/assets/test_prelude.ld
index 3dc08a0..b0eeb73 100644
--- a/assets/test_prelude.ld
+++ b/assets/test_prelude.ld
@@ -414,6 +414,7 @@ fn print! {
 	"Sends a text representation of Ludus values to the console."
 	(...args) -> {
 		let line = do args > map (string, _) > join (_, " ")
+		base :print! (args)
 		update! (console, append (_, line))
 		:ok
 	}
diff --git a/sandbox.ld b/sandbox.ld
index 8e6f6cb..2a0efc4 100644
--- a/sandbox.ld
+++ b/sandbox.ld
@@ -1,16 +1,20 @@
-fn simple_reporter () -> {
+fn reporter () -> {
   print! (self (), msgs ())
 }
 
-fn hanger () -> hanger ()
+fn printer () -> {
+  print!("LUDUS SAYS ==> hi")
+  sleep! (1)
+  printer ()
+}
 
-let foo = spawn! (hanger)
-let bar = spawn! (simple_reporter)
-let baz = spawn! (fn () -> panic! :oops)
 
-send (foo, [:foo, :bar, :baz])
-send (bar, (1, 2, 3))
+let foo = spawn! (printer)
+let bar = spawn! (reporter)
 
-yield! ()
+send (bar, [:foo, :bar, :baz])
+
+& yield! ()
+sleep! (5)
 
 :done
diff --git a/src/lib.rs b/src/lib.rs
index 063bee8..af892a5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -3,7 +3,7 @@ use imbl::HashMap;
 use wasm_bindgen::prelude::*;
 
 const DEBUG_SCRIPT_COMPILE: bool = false;
-const DEBUG_SCRIPT_RUN: bool = true;
+const DEBUG_SCRIPT_RUN: bool = false;
 const DEBUG_PRELUDE_COMPILE: bool = false;
 const DEBUG_PRELUDE_RUN: bool = false;
 
diff --git a/src/vm.rs b/src/vm.rs
index f36c1ff..06f222b 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -292,14 +292,15 @@ impl Creature {
                 self.push(Value::Keyword("ok"));
             }
             "spawn" => {
-                println!("spawning new process!");
                 let f = args[1].clone();
                 let proc = Creature::spawn(f, self.zoo.clone(), self.debug);
                 let id = self.zoo.as_ref().borrow_mut().put(proc);
+                println!("spawning new process {id}!");
                 self.push(Value::Keyword(id));
             }
             "yield" => {
                 self.r#yield = true;
+                println!("yielding from {}", self.id);
                 self.push(Value::Keyword("ok"));
             }
             "alive" => {
@@ -318,7 +319,15 @@ impl Creature {
                 self.mbx = VecDeque::new();
                 self.push(Value::Keyword("ok"));
             }
-            "sleep" => {}
+            "sleep" => {
+                println!("sleeping {} for {}", self.id, args[1]);
+                let Value::Number(ms) = args[1] else {
+                    unreachable!()
+                };
+                self.zoo.as_ref().borrow_mut().sleep(self.id, ms as usize);
+                self.r#yield = true;
+                self.push(Value::Keyword("ok"));
+            }
             msg => panic!("Process does not understand message: {msg}"),
         }
     }
diff --git a/src/world.rs b/src/world.rs
index f44515e..5034323 100644
--- a/src/world.rs
+++ b/src/world.rs
@@ -4,7 +4,9 @@ use crate::vm::{Creature, Panic};
 use ran::ran_u8;
 use std::cell::RefCell;
 use std::collections::HashMap;
+use std::mem::swap;
 use std::rc::Rc;
+use std::time::{Duration, Instant};
 
 const ANIMALS: [&str; 24] = [
     "tortoise",
@@ -67,7 +69,9 @@ pub struct Zoo {
     ids: HashMap<&'static str, usize>,
     dead: Vec<&'static str>,
     kill_list: Vec<&'static str>,
-    active: usize,
+    sleeping: HashMap<&'static str, (Instant, Duration)>,
+    active_idx: usize,
+    active_id: &'static str,
 }
 
 impl Zoo {
@@ -78,7 +82,9 @@ impl Zoo {
             ids: HashMap::new(),
             kill_list: vec![],
             dead: vec![],
-            active: 0,
+            sleeping: HashMap::new(),
+            active_idx: 0,
+            active_id: "",
         }
     }
 
@@ -119,27 +125,63 @@ impl Zoo {
         self.kill_list.push(id);
     }
 
+    pub fn sleep(&mut self, id: &'static str, ms: usize) {
+        self.sleeping
+            .insert(id, (Instant::now(), Duration::from_millis(ms as u64)));
+    }
+
+    pub fn is_alive(&self, id: &'static str) -> bool {
+        if self.kill_list.contains(&id) {
+            return false;
+        }
+        let idx = self.ids.get(id);
+        match idx {
+            Some(idx) => match self.procs.get(*idx) {
+                Some(proc) => match proc {
+                    Status::Empty => false,
+                    Status::Borrowed => true,
+                    Status::Nested(_) => true,
+                },
+                None => false,
+            },
+            None => false,
+        }
+    }
+
     pub fn clean_up(&mut self) {
         while let Some(id) = self.kill_list.pop() {
             if let Some(idx) = self.ids.get(id) {
+                println!("buried process {id}");
                 self.procs[*idx] = Status::Empty;
                 self.empty.push(*idx);
                 self.ids.remove(id);
                 self.dead.push(id);
             }
         }
+
+        self.sleeping
+            .retain(|_, (instant, duration)| instant.elapsed() < *duration);
+
+        println!(
+            "currently sleeping processes: {}",
+            self.sleeping
+                .keys()
+                .map(|id| id.to_string())
+                .collect::<Vec<_>>()
+                .join(" | ")
+        );
     }
 
     pub fn catch(&mut self, id: &'static str) -> Creature {
         if let Some(idx) = self.ids.get(id) {
             let mut proc = Status::Borrowed;
-            std::mem::swap(&mut proc, &mut self.procs[*idx]);
+            swap(&mut proc, &mut self.procs[*idx]);
             let Status::Nested(proc) = proc else {
-                unreachable!("tried to borrow an empty or already-borrowed process");
+                unreachable!("tried to borrow an empty or already-borrowed process {id}");
             };
             proc
         } else {
-            unreachable!("tried to borrow a non-existent process");
+            unreachable!("tried to borrow a non-existent process {id}");
         }
     }
 
@@ -147,46 +189,36 @@ impl Zoo {
         let id = proc.id;
         if let Some(idx) = self.ids.get(id) {
             let mut proc = Status::Nested(proc);
-            std::mem::swap(&mut proc, &mut self.procs[*idx]);
-        } else {
-            unreachable!("tried to return a process the world doesn't know about");
+            swap(&mut proc, &mut self.procs[*idx]);
+        }
+        // Removed because, well, we shouldn't have creatures we don't know about
+        // And since zoo.next now cleans (and thus kills) before the world releases its active process
+        // We'll die if we execute this check
+        // else {
+        //     unreachable!("tried to return a process the world doesn't know about");
+        // }
+    }
+
+    pub fn is_available(&self) -> bool {
+        match &self.procs[self.active_idx] {
+            Status::Empty => false,
+            Status::Borrowed => false,
+            Status::Nested(proc) => !self.sleeping.contains_key(proc.id),
         }
     }
 
-    pub fn next(&mut self, curr_id: &'static str) -> &'static str {
-        println!("getting next process from {curr_id}");
-        println!(
-            "current procs in zoo:\n{}",
-            self.procs
-                .iter()
-                .map(|proc| proc.to_string())
-                .collect::<Vec<_>>()
-                .join("//")
-        );
-        println!("ids: {:?}", self.ids);
-        let idx = self.ids.get(curr_id).unwrap();
-        println!("current idx: {idx}");
-        if *idx != self.active {
-            panic!(
-                "tried to get next creature after {curr_id} while {} is active",
-                self.active
+    pub fn next(&mut self) -> &'static str {
+        self.active_idx = (self.active_idx + 1) % self.procs.len();
+        while !self.is_available() {
+            self.clean_up();
+            self.active_idx = (self.active_idx + 1) % self.procs.len();
+            println!(
+                "testing process availability: {}",
+                self.procs[self.active_idx]
             );
         }
-        self.active = (self.active + 1) % self.procs.len();
-        println!("active idx is now: {}", self.active);
-        while self.procs[self.active] == Status::Empty {
-            let new_active_idx = (self.active + 1) % self.procs.len();
-            println!("new active idx: {new_active_idx}");
-            println!("new active process is: {}", self.procs[new_active_idx]);
-            self.active = (self.active + 1) % self.procs.len();
-        }
-        println!("found next proc: {}", &self.procs[self.active]);
-        match &self.procs[self.active] {
-            Status::Empty => unreachable!(),
-            Status::Borrowed => panic!(
-                "encountered unexpectedly borrowed process at idx {}",
-                self.active
-            ),
+        match &self.procs[self.active_idx] {
+            Status::Empty | Status::Borrowed => unreachable!(),
             Status::Nested(proc) => proc.id,
         }
     }
@@ -231,26 +263,42 @@ impl World {
     //     proc.receive(msg);
     //     self.zoo.release(proc);
     // }
-
+    //
     fn next(&mut self) {
-        let id = self
-            .zoo
-            .as_ref()
-            .borrow_mut()
-            .next(self.active.as_ref().unwrap().id);
-        println!("next id is {id}");
         let mut active = None;
-        std::mem::swap(&mut active, &mut self.active);
-        let mut holding_pen = self.zoo.as_ref().borrow_mut().catch(id);
-        let mut active = active.unwrap();
-        std::mem::swap(&mut active, &mut holding_pen);
-        println!("now in the holding pen: {}", holding_pen.id);
-        holding_pen.reset_reductions();
-        self.zoo.as_ref().borrow_mut().release(holding_pen);
-        let mut active = Some(active);
-        std::mem::swap(&mut active, &mut self.active);
+        swap(&mut active, &mut self.active);
+        let mut zoo = self.zoo.as_ref().borrow_mut();
+        zoo.release(active.unwrap());
+        // at the moment, active is None, process is released.
+        // zoo should NOT need an id--it has a representation of the current active process
+        // world has an active process for memory reasons
+        // not for state-keeping reasons
+        let new_active_id = zoo.next();
+        let mut new_active_proc = zoo.catch(new_active_id);
+        new_active_proc.reset_reductions();
+        let mut new_active_opt = Some(new_active_proc);
+        swap(&mut new_active_opt, &mut self.active);
     }
 
+    // fn old_next(&mut self) {
+    //     let id = self
+    //         .zoo
+    //         .as_ref()
+    //         .borrow_mut()
+    //         .next(self.active.as_ref().unwrap().id);
+    //     println!("next id is {id}");
+    //     let mut active = None;
+    //     std::mem::swap(&mut active, &mut self.active);
+    //     let mut holding_pen = self.zoo.as_ref().borrow_mut().catch(id);
+    //     let mut active = active.unwrap();
+    //     std::mem::swap(&mut active, &mut holding_pen);
+    //     println!("now in the holding pen: {}", holding_pen.id);
+    //     holding_pen.reset_reductions();
+    //     self.zoo.as_ref().borrow_mut().release(holding_pen);
+    //     let mut active = Some(active);
+    //     std::mem::swap(&mut active, &mut self.active);
+    // }
+
     // pub fn sleep(&mut self, id: &'static str) {
     //     // check if the id is the actually active process
     //     if self.active.id != id {
@@ -299,16 +347,15 @@ impl World {
         &self.active.as_ref().unwrap().result
     }
 
-    pub fn clean_up(&mut self) {
-        self.zoo.as_ref().borrow_mut().clean_up()
-    }
-
     pub fn run(&mut self) {
         self.activate_main();
         loop {
-            println!("entering world loop");
+            println!(
+                "entering world loop; active process is {}",
+                self.active_id()
+            );
             self.active.as_mut().unwrap().interpret();
-            println!("interpreted loop");
+            println!("yielded from {}", self.active_id());
             match self.active_result() {
                 None => (),
                 Some(_) => {
@@ -316,12 +363,13 @@ impl World {
                         self.result = self.active_result().clone();
                         return;
                     }
+                    println!("process died: {}", self.active_id());
                     self.kill_active();
                 }
             }
             println!("getting next process");
             self.next();
-            self.clean_up();
+            // self.clean_up();
         }
     }