diff --git a/build/ludus.mjs b/build/ludus.mjs
index 4c70165..2296127 100644
--- a/build/ludus.mjs
+++ b/build/ludus.mjs
@@ -6,25 +6,22 @@ let result = null
 
 export function run (source) {
   const output = mod.ludus(source).value
-  // console.log(output)
   result = JSON.parse(output)
   return result
 }
 
 export function stdout () {
+  if (!result) return ""
   return result.io.console.data
 }
 
 export function turtle_commands () {
+  if (!result) return []
   return result.io.turtle.data
 }
 
-export function p5_calls () {
-  return p5_call_list
-}
-
 export function svg () {
-  
+  // TODO
 }
 
 const turtle_init = {
@@ -55,13 +52,14 @@ const colors = {
 	aqua: [0, 255, 25, 255],
 }
 
-let turtle_states = [turtle_init]
-let background_color = "black"
-
-function last_state () {
-  return turtle_states[turtle_states.length - 1]
+function resolve_color (color) {
+  if (typeof color === 'string') return colors[color]
+  if (typeof color === 'number') return [color, color, color, 255]
+  if (Array.isArray(color)) return color
 }
 
+let background_color = "black"
+
 function add (v1, v2) {
   const [x1, y1] = v1
   const [x2, y2] = v2
@@ -76,83 +74,84 @@ function mult (vector, scalar) {
 function unit_of (heading) {
   const turns = -heading + 0.25
   const radians = turn_to_rad(turns)
-  [Math.cos (radians), Math.sin(radians)]
+  return [Math.cos(radians), Math.sin(radians)]
 }
 
-function command_to_state (previous, command) {
-  const verb = command[0]
+function command_to_state (prev_state, curr_command) {
+  const verb = curr_command[0]
   switch (verb) {
     case "goto": {
-      const [_, x, y] = command
-      return {...previous, position: [x, y]}
+      const [_, x, y] = curr_command
+      return {...prev_state, position: [x, y]}
     }
     case "home": {
-      return {...previous, position: [0, 0], heading: 0}
+      return {...prev_state, position: [0, 0], heading: 0}
     }
     case "right": {
-      const [_, angle] = command
-      const {heading} = previous
-      return {...previous, heading: heading + angle}
+      const [_, angle] = curr_command
+      const {heading} = prev_state
+      return {...prev_state, heading: heading + angle}
     }
     case "left": {
-      const [_, angle] = command
-      const {heading} = previous
-      return {...previous, heading: heading - angle}
+      const [_, angle] = curr_command
+      const {heading} = prev_state
+      return {...prev_state, heading: heading - angle}
     }
     case "forward": {
-      const [_, steps] = command
-      const {heading, position} = previous
+      const [_, steps] = curr_command
+      const {heading, position} = prev_state
       const unit = unit_of(heading)
       const move = mult(unit, steps)
-      return {...previous, position: add(position, move)}
+      return {...prev_state, position: add(position, move)}
     }
     case "back": {
-      const [_, steps] = command
-      const {heading, position} = previous
+      const [_, steps] = curr_command
+      const {heading, position} = prev_state
       const unit = unit_of(heading)
       const move = mult(unit, -steps)
-      return {...previous, position: add(position, move)}
+      return {...prev_state, position: add(position, move)}
     }
     case "penup": {
-      return {...previous, pendown: false}
+      return {...prev_state, pendown: false}
     }
     case "pendown": {
-      return {...previous, pendown: true}
+      return {...prev_state, pendown: true}
     }
     case "pendwith": {
-      const [_, width] = command
-      return {...previous, penwidth: width}
+      const [_, width] = curr_command
+      return {...prev_state, penwidth: width}
     }
     case "pencolor": {
-      if (command.length = 2) {
-        const [_, color] = command
-        return {...previous, pencolor: color}
+      console.log(curr_command)
+      if (curr_command.length = 2) {
+        const [_, color] = curr_command
+        return {...prev_state, pencolor: color}
       } else {
-        const [_, r, g, b, a] = command
-        return {...previous, pencolor: [r, g, b, a]}
+        const [_, r, g, b, a] = curr_command
+        return {...prev_state, pencolor: [r, g, b, a]}
       }
     }
     case "setheading": {
-      const [_, heading] = command
-      return {...previous, heading: heading}
+      const [_, heading] = curr_command
+      return {...prev_state, heading: heading}
     }
     case "loadstate": {
-      const [_, x, y, heading, visible, pendown, penwidth] = command
+      const [_, x, y, heading, visible, pendown, penwidth] = curr_command
       // there are 7 fixed-arity arguments
       // color will either be the last one or four
-      let pencolor = command.slice(7)
+      let pencolor = curr_command.slice(7)
       // if there's one, it's a string, unpack it
       if (pencolor.length = 1) pencolor = pencolor[0]
       return {position: [x, y], heading, visible, pendown, penwidth, pencolor}
     }
     case "show": {
-      return {...position, visible: true}
+      return {...prev_state, visible: true}
     }
     case "hide": {
-      return {...position, visible: false}
+      return {...prev_state, visible: false}
     }
     case "background": {
-      let color = command.slice(1)
+      let color = curr_command.slice(1)
       if (color.lengh = 1) color = color[0]
       background_color = color
       return
@@ -166,8 +165,26 @@ function are_eq (v1, v2) {
   return (x1 === x2) && (y1 === y2)
 }
 
-function state_to_call (prev, curr) {
-  
+function states_to_call (prev, curr) {
+  const calls = []
+  // whose state should we use?
+  // pen states will only differ on more than one property
+  // if we use `loadstate`
+  // my sense is `prev`, but that may change
+  if (prev.pendown && !are_eq(prev.position, curr.position)) {
+    calls.push(["line", prev.position[0], prev.position[1], curr.position[0], curr.position[1]])
+  }
+  if (curr.pencolor !== prev.pencolor) {
+    if (Array.isArray(curr.pencolor)) {
+      calls.push(["stroke", ...curr.pencolor])
+    } else {
+      calls.push(["stroke", curr.pencolor])
+    }
+  }
+  if (curr.penwidth !== prev.penwidth) {
+    calls.push(["strokeWeight", curr.penwidth])
+  }
+  return calls
 }
 
 const turtle_radius = 20
@@ -176,47 +193,65 @@ const turtle_angle = 0.385
 
 const turtle_color = [255, 255, 255, 150]
 
-let p5_call_list = []
-
-function add_p5_call (call) {
-  p5_call_list.push(call)
-}
+const p5_call_root = [
+  ["background", ...resolve_color(background_color)],
+  ["stroke", ...resolve_color(turtle_init.pencolor)]
+]
 
 function rotate (vector, heading) {
   const radians = turn_to_rad(heading)
   const [x, y] = vector
   return [
-    (x * cos (radians)) - (y * sin (radians)),
-    (x * sin (radians)) + (y * cos (radians))
+    (x * Math.cos (radians)) - (y * Math.sin (radians)),
+    (x * Math.sin (radians)) + (y * Math.cos (radians))
   ]
 }
 
 function turn_to_rad (heading) {
-  heading * 2 * Math.PI
+  return heading * 2 * Math.PI
 }
 
-function render_turtle () {
-  const state = last_state ()
+function render_turtle (state, calls) {
   if (!state.visible) return
+  calls.push(["push"])
   const [r, g, b, a] = turtle_color
-  add_call("fill", r, g, b, a)
-  const {heading, pencolor: [pen_r, pen_g, pen_b, pen_a], position: [x, y], pendown} = state
+  calls.push(["fill", r, g, b, a])
+  const {heading, pencolor, position: [x, y], pendown} = state
   const origin = [0, turtle_radius]
   const [x1, y1] = origin
   const [x2, y2] = rotate(origin, turtle_angle)
   const [x3, y3] = rotate(origin, -turtle_angle)
-  add_p5_call(["push"])
-  add_p5_call(["translate", x, y])
-  add_p5_call(["rotate", turn_to_rad(heading)])
-  add_p5_call(["noStroke"])
-  add_p5_call(["beginShape"])
-  add_p5_call(["vertex", x1, y1])
-  add_p5_call(["vertex", x2, y2])
-  add_p5_call(["vertex", x3, y3])
-  add_p5_call(["endShape"])
-  add_p5_call(["stroke", pen_r, pen_g, pen_b, pen_a])
-  if (pendown) add_p5_call(["line", 0, 0, x1, y1])
-  add_p5_call(["pop"])
+  calls.push(["translate", x, y])
+  calls.push(["rotate", turn_to_rad(heading)])
+  calls.push(["noStroke"])
+  calls.push(["beginShape"])
+  calls.push(["vertex", x1, y1])
+  calls.push(["vertex", x2, y2])
+  calls.push(["vertex", x3, y3])
+  calls.push(["endShape"])
+  calls.push(["stroke", ...resolve_color(pencolor)])
+  if (pendown) calls.push(["line", 0, 0, x1, y1])
+  calls.push(["pop"])
+  return calls
 }
 
-
+export function p5_calls (commands) {
+  const states = [turtle_init]
+  commands.reduce((prev_state, command) => {
+    const new_state = command_to_state(prev_state, command)
+    states.push(new_state)
+    return new_state
+  }, turtle_init)
+  const p5_calls = [...p5_call_root]
+  for (let i = 1; i < states.length; ++i) {
+    const prev = states[i - 1]
+    const curr = states[i]
+    const calls = states_to_call(prev, curr)
+    for (const call of calls) {
+      p5_calls.push(call)
+    }
+  }
+  p5_calls[0] = ["background", ...resolve_color(background_color)]
+  render_turtle(states[states.length - 1], p5_calls)
+  return p5_calls
+}