diff --git a/assets/test_prelude.ld b/assets/test_prelude.ld
index 8325121..963e67f 100644
--- a/assets/test_prelude.ld
+++ b/assets/test_prelude.ld
@@ -791,16 +791,16 @@ fn range {
 & additional list operations now that we have comparitors
 fn at {
 	"Returns the element at index n of a list or tuple, or the byte at index n of a string. Zero-indexed: the first element is at index 0. Returns nil if nothing is found in a list or tuple; returns an empty string if nothing is found in a string."
-	(xs as :list, n as :number) -> base :nth (n, xs)
-	(xs as :tuple, n as :number) -> base :nth (n, xs)
-	(str as :string, n as :number) -> {
-		let raw = base :nth (n, str)
-		when {
-			nil? (raw) -> nil
-			gte? (raw, 128) -> panic! "not an ASCII char"
-			true -> base :str_slice (str, n, inc (n))
-		}
-	}
+	(xs as :list, n as :number) -> base :at (xs, n)
+	(xs as :tuple, n as :number) -> base :at (xs, n)
+	& (str as :string, n as :number) -> {
+	& 	let raw = base :at (str, n)
+	& 	when {
+	& 		nil? (raw) -> nil
+	& 		gte? (raw, 128) -> panic! "not an ASCII char"
+	& 		true -> base :str_slice (str, n, inc (n))
+	& 	}
+	& }
 	(_) -> nil
 }
 
@@ -819,11 +819,6 @@ fn last {
 	(xs) if ordered? (xs) -> at (xs, dec (count (xs)))
 }
 
-fn butlast {
-	"Returns a list, omitting the last element."
-	(xs as :list) -> base :slice (xs, 0, dec (count (xs)))
-}
-
 fn slice {
 	"Returns a slice of a list or a string, representing a sub-list or sub-string."
 	(xs as :list, end as :number) -> slice (xs, 0, end) 
@@ -837,6 +832,11 @@ fn slice {
 	(str as :string, start as :number, end as :number) -> base :str_slice (str, start, end)
 }
 
+fn butlast {
+	"Returns a list, omitting the last element."
+	(xs as :list) -> slice (xs, 0, dec (count (xs)))
+}
+
 &&& keywords: funny names
 fn keyword? {
 	"Returns true if a value is a keyword, otherwise returns false."
@@ -860,10 +860,21 @@ fn dissoc {
 	(d as :dict, k as :keyword) -> base :dissoc (d, k)
 }
 
+& TODO: consider merging `get` and `at`
+fn get {
+	"Takes a key, dict, and optional default value; returns the value at key. If the value is not found, returns nil or the default value."
+	(k as :keyword) -> get (k, _)
+	(k as :keyword, d as :dict) -> base :get (d, k)
+	(k as :keyword, d as :dict, default) -> match base :get (d, k) with {
+		nil -> default
+		val -> val
+	} 
+}
+
 fn update {
 	"Takes a dict, key, and function, and returns a new dict with the key set to the result of applying the function to original value held at the key."
 	(d as :dict) -> d
-	(d as :dict, k as :keyword, updater as :fn) -> base :assoc (d, k, updater (k (d)))
+	(d as :dict, k as :keyword, updater as :fn) -> assoc (d, k, updater (get (k, d)))
 }
 
 fn keys {
@@ -876,19 +887,11 @@ fn values {
 	(d as :dict) -> do d > list > map (second, _)
 }
 
-& TODO: consider merging `get` and `at`
-fn get {
-	"Takes a key, dict, and optional default value; returns the value at key. If the value is not found, returns nil or the default value."
-	(k as :keyword) -> get (k, _)
-	(k as :keyword, d as :dict) -> get (k, d, nil)
-	(k as :keyword, d as :dict, default) -> base :get (k, d, default) 
-}
-
 & TODO: add sets to this?
 fn has? {
 	"Takes a key and a dict, and returns true if there is a non-`nil` value stored at the key."
 	(k as :keyword) -> has? (k, _)
-	(k as :keyword, d as :dict) -> do d > k > some?
+	(k as :keyword, d as :dict) -> do d > get (k) > some?
 }
 
 fn dict {
@@ -938,9 +941,273 @@ fn random_int {
 }
 
 
+&&& Results, errors and other unhappy values
 
+fn ok {
+	"Takes a value and wraps it in an :ok result tuple."
+	(value) -> (:ok, value)	
+}
 
+fn ok? {
+	"Takes a value and returns true if it is an :ok result tuple."
+	((:ok, _)) -> true
+	(_) -> false
+}
 
+fn err {
+	"Takes a value and wraps it in an :err result tuple, presumably as an error message."
+	(msg) -> (:err, msg)
+}
+
+fn err? {
+	"Takes a value and returns true if it is an :err result tuple."
+	((:err, _)) -> true
+	(_) -> false
+}
+
+fn unwrap! {
+	"Takes a result tuple. If it's :ok, then returns the value. If it's not :ok, then it panics. If it's not a result tuple, it also panics."
+	((:ok, value)) -> value
+	((:err, msg)) -> panic! string ("Unwrapped :err! ", msg)
+	(_) -> panic! "Cannot unwrap something that's not an error tuple."
+}
+
+fn unwrap_or {
+	"Takes a value that is a result tuple and a default value. If it's :ok, then it returns the value. If it's :err, returns the default value."
+	((:ok, value), _) -> value
+	((:err, _), default) -> default
+}
+
+fn assert! {
+	"Asserts a condition: returns the value if the value is truthy, panics if the value is falsy. Takes an optional message."
+	(value) -> if value 
+		then value 
+		else panic! "Assert failed: {value}"
+	(msg, value) -> if value 
+		then value 
+		else panic! "Assert failed: {msg} with {value}"
+}
+
+&&& Turtle & other graphics
+
+& some basic colors
+& these are the "basic" css colors
+& https://developer.mozilla.org/en-US/docs/Web/CSS/named-color
+let colors = #{
+	:black (0, 0, 0, 255)
+	:silver (192, 192, 192, 255)
+	:gray (128, 128, 128, 255)
+	:white (255, 255, 255, 255)
+	:maroon (128, 0, 0, 255)
+	:red (255, 0, 0, 255)
+	:purple (128, 0, 128, 255)
+	:fuchsia (255, 0, 255, 255)
+	:green (0, 128, 0, 255)
+	:lime (0, 255, 0, 255)
+	:olive (128, 128, 0, 255)
+	:yellow (255, 255, 0, 255)
+	:navy (0, 0, 128, 255)
+	:blue (0, 0, 255, 255)
+	:teal (0, 128, 128, 255)
+	:aqua (0, 255, 25, 255)
+}
+
+& the initial turtle state
+let turtle_init = #{
+	:position (0, 0) & let's call this the origin for now
+	:heading 0 & this is straight up
+	:pendown? true
+	:pencolor :white
+	:penwidth 1
+	:visible? true
+}
+
+& turtle states: refs that get modified by calls
+& turtle_commands is a list of commands, expressed as tuples
+box turtle_commands = []
+box turtle_state = turtle_init
+
+fn apply_command
+
+fn add_command! (command) -> {
+	update! (turtle_commands, append (_, command))
+	let prev = unbox (turtle_state)
+	let curr = apply_command (prev, command)
+	store! (turtle_state, curr)
+	:ok
+}
+
+fn forward! {
+	"Moves the turtle forward by a number of steps. Alias: fd!"
+	(steps as :number) -> add_command! ((:forward, steps))
+}
+
+let fd! = forward!
+
+fn back! {
+	"Moves the turtle backward by a number of steps. Alias: bk!"
+	(steps as :number) -> add_command! ((:back, steps))
+}
+
+let bk! = back!
+
+fn left! {
+	"Rotates the turtle left, measured in turns. Alias: lt!"
+	(turns as :number) -> add_command! ((:left, turns))
+}
+
+let lt! = left!
+
+fn right! {
+	"Rotates the turtle right, measured in turns. Alias: rt!"
+	(turns as :number) -> add_command! ((:right, turns))
+}
+
+let rt! = right!
+
+fn penup! {
+	"Lifts the turtle's pen, stopping it from drawing. Alias: pu!"
+	() -> add_command! ((:penup))
+}
+
+let pu! = penup!
+
+fn pendown! {
+	"Lowers the turtle's pen, causing it to draw. Alias: pd!"
+	() -> add_command! ((:pendown))
+}
+
+let pd! = pendown!
+
+fn pencolor! {
+	"Changes the turtle's pen color. Takes a single grayscale value, an rgb tuple, or an rgba tuple. Alias: pc!"
+	(color as :keyword) -> add_command! ((:pencolor, color))
+	(gray as :number) -> add_command! ((:pencolor, (gray, gray, gray, 255)))
+	((r as :number, g as :number, b as :number)) -> add_command! ((:pencolor, (r, g, b, 255)))
+	((r as :number, g as :number, b as :number, a as :number)) -> add_command! ((:pencolor, (r, g, b, a)))
+}
+
+let pc! = pencolor!
+
+fn penwidth! {
+	"Sets the width of the turtle's pen, measured in pixels. Alias: pw!"
+	(width as :number) -> add_command! ((:penwidth, width))
+}
+
+let pw! = penwidth!
+
+fn background! {
+	"Sets the background color behind the turtle and path. Alias: bg!"
+	(color as :keyword) -> add_command! ((:background, color))
+	(gray as :number) -> add_command! ((:background, (gray, gray, gray, 255)))
+	((r as :number, g as :number, b as :number)) -> add_command! ((:background, (r, g, b, 255)))
+	((r as :number, g as :number, b as :number, a as :number)) -> add_command! ((:background, (r, g, b, a)))
+}
+
+let bg! = background!
+
+fn home! {
+	"Sends the turtle home: to the centre of the screen, pointing up. If the pen is down, the turtle will draw a path to home."
+	() -> add_command! ((:home))
+}
+
+fn clear! {
+	"Clears the canvas and sends the turtle home."
+	() -> add_command! ((:clear))
+}
+
+fn goto! {
+	"Sends the turtle to (x, y) coordinates. If the pen is down, the turtle will draw a path to its new location."
+	(x as :number, y as :number) -> add_command! ((:goto, (x, y)))
+	((x, y)) -> goto! (x, y)
+}
+
+fn setheading! {
+	"Sets the turtle's heading. The angle is specified in turns, with 0 pointing up. Increasing values rotate the turtle counter-clockwise."
+	(heading as :number) -> add_command! ((:setheading, heading))
+}
+
+fn showturtle! {
+	"If the turtle is hidden, shows the turtle. If the turtle is already visible, does nothing."
+	() -> add_command! ((:show))
+}
+
+fn hideturtle! {
+	"If the turtle is visible, hides it. If the turtle is already hidden, does nothing."
+	() -> add_command! ((:hide))
+}
+
+fn loadstate! {
+	"Sets the turtle state to a previously saved state."
+	(state) -> {
+		let #{position, heading, pendown?, pencolor, penwidth, visible?} = state
+		add_command! ((:loadstate, position, heading, visible?, pendown?, penwidth, pencolor))
+	}
+}
+
+fn apply_command {
+	"Takes a turtle state and a command and calculates a new state."
+	(state, command) -> match command with {
+		(:goto, (x, y)) -> assoc (state, :position, (x, y))
+		(:home) -> do state > 
+			assoc (_, :position, (0, 0)) >
+			assoc (_, :heading, 0)
+		(:clear) -> do state >
+			assoc (state, :position, (0, 0)) >
+			assoc (_, :heading, 0)
+		(:right, turns) -> update (state, :heading, add (_, turns))
+		(:left, turns) -> update (state, :heading, sub (_, turns))
+		(:forward, steps) -> {
+			let #{heading, position, ...} = state
+			let unit = heading/vector (heading)
+			let vect = mult (steps, unit)
+			update (state, :position, add (vect, _))
+		}
+		(:back, steps) -> {
+			let #{heading, position, ...} = state
+			let unit = heading/vector (heading)
+			let vect = mult (steps, unit)
+			update (state, :position, sub (_, vect))
+		}
+		(:penup) -> assoc (state, :pendown?, false)
+		(:pendown) -> assoc (state, :pendown?, true)
+		(:penwidth, pixels) -> assoc (state, :penwidth, pixels)
+		(:pencolor, color) -> assoc (state, :pencolor, color)
+		(:setheading, heading) -> assoc (state, :heading, heading)
+		(:loadstate, position, heading, visible?, pendown?, penwidth, pencolor) -> #{position, heading, visible?, pendown?, penwidth, pencolor}
+		(:show) -> assoc (state, :visible?, true)
+		(:hide) -> assoc (state, :visible?, false)
+		(:background, _) -> state
+	}
+}
+
+& position () -> (x, y)
+fn position {
+	"Returns the turtle's current position."
+	() -> do turtle_state > unbox > :position
+}
+
+fn heading {
+	"Returns the turtle's current heading."
+	() -> do turtle_state > unbox > :heading
+}
+
+fn pendown? {
+	"Returns the turtle's pen state: true if the pen is down."
+	() -> do turtle_state > unbox > :pendown?
+}
+
+fn pencolor {
+	"Returns the turtle's pen color as an (r, g, b, a) tuple or keyword."
+	() -> do turtle_state > unbox > :pencolor
+}
+
+fn penwidth {
+	"Returns the turtle's pen width in pixels."
+	() -> do turtle_state > unbox > :penwidth
+}
+
+box state = nil
 
 #{
   type
@@ -1065,4 +1332,46 @@ fn random_int {
 	each!
 	random
 	random_int
+	ok
+	ok?
+	err
+	err?
+	unwrap!
+	unwrap_or
+	assert!
+	colors
+	turtle_init
+	turtle_commands
+	turtle_state
+	forward!
+	fd!
+	back!
+	bk!
+	left!
+	lt!
+	right!
+	rt!
+	penup!
+	pu!
+	pendown!
+	pd!
+	pencolor!
+	pc!
+	penwidth!
+	pw!
+	background!
+	bg!
+	home!
+	clear!
+	goto!
+	setheading!
+	showturtle!
+	hideturtle!
+	loadstate!
+	position
+	heading
+	pendown?
+	pencolor
+	penwidth
+	state
 }
diff --git a/may_2025_thoughts.md b/may_2025_thoughts.md
index 8e12ac9..938700e 100644
--- a/may_2025_thoughts.md
+++ b/may_2025_thoughts.md
@@ -488,4 +488,8 @@ Currently fixing little bugs in prelude.
 Here's a list of things that need doing:
 * [ ] Escape characters in strings: \n, \t, and \{,  \}.
 * [ ] `doc!` needs to print the patterns of a function.
+* [ ] I need to return to the question of whether/how strings are ordered; do we use `at`, or do we want `char_at`? etc.
+* [ ] Original implementation of `butlast` is breaking stack discipline; I don't know why. It ends up returning from evaluating one of the arguments straight into a `load` instruction. Something about tail calls and ternary synthetic expressions and base functions. (For now, I can call `slice` instead of `base :slice` and it works.)
+    - Original version of `update` also had this same problem with `assoc`; fixed it by calling the Ludus, rather than Rust, function.
+    - I need this fixed for optimization reasons.
 
diff --git a/sandbox.ld b/sandbox.ld
index 0a54d57..cc29d5b 100644
--- a/sandbox.ld
+++ b/sandbox.ld
@@ -1,7 +1,12 @@
-when {
-	false -> :no
-	nil -> :nope
-	:else -> :yup
+let command = (:forward, 100)
+
+match command with {
+	(:goto, (x, y)) -> "goto: {x} and {y}"
+	(:home) -> "go home!"
+	& (:clear) -> "clear the screen"
+	& (:right, turns) -> "make {turns} to the right"
+	& (:left, turns) -> "turn left! by {turns}"
+	(:forward, steps) -> "forward {steps} turtle paces"
+	(:back, steps) -> "flip it and reverse it {steps}"
 }
 
-
diff --git a/src/compiler.rs b/src/compiler.rs
index 1f9eb15..687722b 100644
--- a/src/compiler.rs
+++ b/src/compiler.rs
@@ -607,7 +607,7 @@ impl<'a> Compiler<'a> {
 
                 // patch up the previous no match jumps to jump to clean-up code
                 for idx in jump_idxes {
-                    self.patch_jump(idx, self.len() - idx - 2)
+                    self.patch_jump(idx, self.len() - idx - 3)
                 }
                 // pop everything that was pushed
                 // don't change the compiler stack representation, tho
diff --git a/src/main.rs b/src/main.rs
index 52d8542..70eb87e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -112,8 +112,8 @@ pub fn run(src: &'static str) {
     // in any event, the AST should live forever
     let parsed: &'static Spanned<Ast> = Box::leak(Box::new(parse_result.unwrap()));
 
-    // let prelude = prelude();
-    let prelude = imbl::HashMap::new();
+    let prelude = prelude();
+    // let prelude = imbl::HashMap::new();
 
     let mut validator = Validator::new(&parsed.0, &parsed.1, "user input", src, prelude.clone());
     validator.validate();
diff --git a/src/vm.rs b/src/vm.rs
index 77d1ac4..3c725f7 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -976,6 +976,10 @@ impl Vm {
                             self.ip = self.frame.ip;
                             // finally, throw the value on the stack
                             self.push(value);
+                            println!(
+                                "=== returning to {} ===",
+                                self.frame.function.as_fn().name()
+                            );
                         }
                         Value::Partial(partial) => {
                             let last_arg = self.pop();