diff --git a/appendix/external-bus.typ b/appendix/external-bus.typ
index 57b83f3..bf0a4d1 100644
--- a/appendix/external-bus.typ
+++ b/appendix/external-bus.typ
@@ -10,7 +10,7 @@
 ]
 
 #let bus-diagram = (addr: array, rd: array, wr: array, a15: array, cs: array, data: array, sampling-edge: false) => {
-  import timing: *
+  import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
   text(13pt,
     diagram(
       grid: true,
@@ -40,7 +40,7 @@
 
 #figure(
   {
-    import timing: *
+    import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
     bus-diagram(
       addr: (u(10),),
       rd: (e(1), l(9),),
@@ -57,7 +57,7 @@
 
 #figure(
   {
-    import timing: *
+    import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
     [
       #columns(2, [
         #block(
@@ -120,7 +120,7 @@
 )
 #figure(
   {
-    import timing: *
+    import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
     [
       #columns(2, [
         #block(
@@ -182,7 +182,7 @@
 
 #figure(
   {
-    import timing: *
+    import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
     [
       #columns(2, [
         #block(
diff --git a/chapter/cpu/instruction-set.typ b/chapter/cpu/instruction-set.typ
index 727e674..f804d0f 100644
--- a/chapter/cpu/instruction-set.typ
+++ b/chapter/cpu/instruction-set.typ
@@ -14,7 +14,7 @@
 ]
 
 #let simple-instruction-timing(mnemonic: str, timing_data: dictionary) = timing.diagram(w_scale: 0.9, ..{
-  import timing: *
+  import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
   let duration = timing_data.duration
   (
     (label: "M-cycle", wave: (
@@ -29,7 +29,7 @@
       x(1),
       ..timing_data.mem_rw.enumerate().map(((idx, label)) => {
         let m_cycle = idx + 2
-        if label == "U" { timing.u(8) } else { timing.d(8, label) }
+        if label == "U" { timing.unknown(8) } else { timing.data(8, label) }
       }),
       x(1, opacity: 40%),
     )),
@@ -37,14 +37,14 @@
 })
 
 #let instruction-timing(mnemonic: str, timing_data: dictionary) = timing.diagram(w_scale: 0.9, ..{
-  import timing: *
+  import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
   let duration = timing_data.duration
   let map_cycle_labels(data) = data.enumerate().map(((idx, label)) => {
     let m_cycle = idx + 2
     if label == "U" {
-      timing.u(8)
+      timing.unknown(8)
     } else {
-      timing.d(8, label)
+      timing.data(8, label)
     }
   })
   (
@@ -62,31 +62,31 @@
     )),
     (label: "Addr bus", wave: (
       x(1),
-      timing.d(8, [Previous], opacity: 40%),
+      timing.data(8, [Previous], opacity: 40%),
       ..map_cycle_labels(timing_data.addr),
       x(1, opacity: 40%),
     )),
     (label: "Data bus", wave: (
       x(1),
-      timing.d(8, [IR ← mem], opacity: 40%),
+      timing.data(8, [IR ← mem], opacity: 40%),
       ..map_cycle_labels(timing_data.data),
       x(1, opacity: 40%),
     )),
     (label: "IDU op", wave: (
       x(1),
-      timing.d(8, [Previous], opacity: 40%),
+      timing.data(8, [Previous], opacity: 40%),
       ..map_cycle_labels(timing_data.idu_op),
       x(1, opacity: 40%),
     )),
     (label: "ALU op", wave: (
       x(1),
-      timing.d(8, [Previous], opacity: 40%),
+      timing.data(8, [Previous], opacity: 40%),
       ..map_cycle_labels(timing_data.alu_op),
       x(1, opacity: 40%),
     )),
     (label: "Misc op", wave: (
       x(1),
-      timing.d(8, [Previous], opacity: 40%),
+      timing.data(8, [Previous], opacity: 40%),
       ..map_cycle_labels(timing_data.misc_op),
       x(1, opacity: 40%),
     )),
diff --git a/chapter/cpu/timing.typ b/chapter/cpu/timing.typ
index df3e5d9..bacc55e 100644
--- a/chapter/cpu/timing.typ
+++ b/chapter/cpu/timing.typ
@@ -44,7 +44,7 @@ The following timing diagram shows all memory operations done by the CPU, and
 the fetch and execute stages of each instruction:
 
 #figure({
-  import timing: *
+  import timing: diagram, clock as c, data as d, either as e, high as h, low as l, unknown as u, undefined as x, high_impedance as z
   diagram(
     w_scale: 0.6, 
     (label: "CLK 4 MiHz", wave: (
diff --git a/timing.typ b/timing.typ
index 2718e8d..6c1e5b4 100644
--- a/timing.typ
+++ b/timing.typ
@@ -1,130 +1,139 @@
 #import "common.typ": cetz, monotext, hex
 
-#let c = (len, ..args) => (type: "C", len: len, ..args.named())
-#let d = (len, label, ..args) => (type: "D", len: len, label: label, ..args.named())
-#let e = (len, ..args) => (type: "E", len: len, ..args.named())
-#let h = (len, ..args) => (type: "H", len: len, ..args.named())
-#let l = (len, ..args) => (type: "L", len: len, ..args.named())
-#let u = (len, ..args) => (type: "U", len: len, ..args.named())
-#let x = (len, ..args) => (type: "X", len: len, ..args.named())
-#let z = (len, ..args) => (type: "Z", len: len, ..args.named())
+#let clock = (len, ..args) => (type: "C", len: len, ..args.named())
+#let data = (len, label, ..args) => (type: "D", len: len, label: label, ..args.named())
+#let either = (len, ..args) => (type: "E", len: len, ..args.named())
+#let high = (len, ..args) => (type: "H", len: len, ..args.named())
+#let low = (len, ..args) => (type: "L", len: len, ..args.named())
+#let unknown = (len, ..args) => (type: "U", len: len, ..args.named())
+#let undefined = (len, ..args) => (type: "X", len: len, ..args.named())
+#let high_impedance = (len, ..args) => (type: "Z", len: len, ..args.named())
 
 #let diagram = (..args, w_scale: 1.0, y_scale: 1.0, grid: false, fg: () => none) => {
   cetz.canvas(length: 0.7em, {
     import cetz.draw
     let x_slope = 0.15 * w_scale;
     let y_step = 2 * y_scale
-    let y_h = 1.0 * y_scale
-    let y_m = 0.5 * y_scale
-    let y_l = 0.0 * y_scale
+
+    let y_level = (H: 1.0 * y_scale, L: 0.0 * y_scale, M: 0.5 * y_scale)
     draw.set-style(stroke: (thickness: 0.07em))
 
     let resolve_level = (prev_state, event) => if event.type == "C" {
-      if prev_state.level == "H" {
-        "L"
-      } else if prev_state.level == "L" {
-        "H"
-      }
+      if prev_state.level == "L" { "H" } else { "L" }
     } else if ("L", "H", "E").contains(event.type) {
       event.type
     } else if ("Z", "X", "D", "U").contains(event.type) {
       "M"
     }
 
+    let invert_level = (level) => if level == "L" { "H" }
+      else if level == "H" { "L" }
+      else { level }
+
     let draw_event = (prev_state, event, next_type) => {
-      let x_start = if ("D", "U").contains(event.type) and prev_state.type != "" { x_slope } else { 0.0 }
-      let x_end = if ("D", "U").contains(next_type) {
-        event.len * w_scale + x_slope
-      } else {
-        event.len * w_scale
-      }
-      if event.type == "L" {
-        if prev_state.level == "H" {
-          draw.line((x_start, y_h), (x_start + x_slope, y_l), (x_end, y_l))
+      let opacity = 100% - (if "opacity" in event { event.opacity } else { 100% })
+      let fg_paint = (if event.type == "X" { red }
+        else if event.type == "Z" { blue }
+        else { black }
+      ).lighten(opacity)
+      let fg_opts = (stroke: if "stroke" in event { event.stroke } else { (paint: fg_paint) })
+
+      let x_start = if ("D", "U").contains(prev_state.type) { x_slope } else { 0.0 }
+      let x_end = event.len * w_scale
+      if event.type == "L" or event.type == "H" {
+        let y = y_level.at(event.type)
+        let y_invert = y_level.at(invert_level(event.type))
+        if prev_state.level == event.type or prev_state.level == "" {
+          draw.line((x_start, y), (x_end, y), ..fg_opts)
         } else if prev_state.level == "E" {
-          draw.line((x_start, y_h), (x_start + x_slope, y_l))
-          draw.line((x_start, y_l), (x_end, y_l))
+          draw.line((x_start, y_invert), (x_start + x_slope, y), ..fg_opts)
+          draw.line((x_start, y), (x_end, y), ..fg_opts)
         } else if prev_state.level == "M" {
-          draw.line((x_start, y_m), (x_start + x_slope, y_l), (x_end, y_l))
-        } else {
-          draw.line((x_start, y_l), (x_end, y_l))
+          draw.line((x_start, y_level.M), (x_start + x_slope, y), (x_end, y), ..fg_opts)
+        } else if prev_state.level == invert_level(event.type) {
+          draw.line((x_start, y_invert), (x_start + x_slope, y), (x_end, y), ..fg_opts)
         }
-      } else if event.type == "H" {
-        if prev_state.level == "L" {
-          draw.line((x_start, y_l), (x_start + x_slope, y_h), (x_end, y_h))
+      } else if event.type == "C" {
+        if prev_state.level == "L" or prev_state.level == "H" {
+          let prev_y = y_level.at(prev_state.level)
+          let y = y_level.at(invert_level(prev_state.level))
+          draw.line((x_start, prev_y), (x_start, y), (x_end, y), ..fg_opts)
         } else if prev_state.level == "E" {
-          draw.line((x_start, y_l), (x_start + x_slope, y_h))
-          draw.line((x_start, y_h), (x_end, y_h))
+          draw.line((x_start, y_level.H), (x_start + x_slope, y_level.L), ..fg_opts)
+          draw.line((x_start, y_level.L), (x_end, y_level.L), ..fg_opts)
         } else if prev_state.level == "M" {
-          draw.line((x_start, y_m), (x_start + x_slope, y_h), (x_end, y_h))
-        } else {
-          draw.line((x_start, y_h), (x_end, y_h))
-        }
-      } else if event.type == "C" {
-        if prev_state.level == "L" {
-          draw.line((x_start, y_l), (x_start, y_scale), (x_end, y_scale))
-        } else if prev_state.level == "H" {
-          draw.line((x_start, y_scale), (x_start, y_l), (x_end, y_l))
+          draw.line((x_start, y_level.M), (x_start + x_slope, y_level.L), (x_end, y_level.L), ..fg_opts)
+        } else if prev_state.level == "" {
+          draw.line((x_start, y_level.L), (x_end, y_level.L), ..fg_opts)
         }
       } else if event.type == "E" {
-        if prev_state.level == "L" {
-          draw.line((x_start, y_l), (x_start + x_slope, y_h), (x_end, y_h))
-        } else if prev_state.level == "M" {
-          draw.line((x_start, y_m), (x_start + x_slope, y_h), (x_end, y_h))
+        if prev_state.level == "L" or prev_state.level == "M" {
+          let y = y_level.at(prev_state.level)
+          draw.line((x_start, y), (x_start + x_slope, y_level.H), (x_end, y_level.H), ..fg_opts)
         } else {
-          draw.line((x_start, y_h), (x_end, y_h))
+          draw.line((x_start, y_level.H), (x_end, y_level.H), ..fg_opts)
         }
-        if prev_state.level == "H" {
-          draw.line((x_start, y_h), (x_start + x_slope, y_l), (x_end, y_l))
-        } else if prev_state.level == "M" {
-          draw.line((x_start, y_m), (x_start + x_slope, y_l), (x_end, y_l))
+        if prev_state.level == "H" or prev_state.level == "M" {
+          let y = y_level.at(prev_state.level)
+          draw.line((x_start, y), (x_start + x_slope, y_level.L), (x_end, y_level.L), ..fg_opts)
         } else {
-          draw.line((x_start, y_l), (x_end, y_l))
+          draw.line((x_start, y_level.L), (x_end, y_level.L), ..fg_opts)
+        }
+      } else if event.type == "X" or event.type == "Z" {
+        if prev_state.level == "L" or prev_state.level == "H" {
+          let y = y_level.at(prev_state.level)
+          draw.line((x_start, y), (x_start + x_slope, y_level.M), (x_end, y_level.M), ..fg_opts)
+        } else if prev_state.level == "M" or prev_state.level == "" {
+          draw.line((x_start, y_level.M), (x_end, y_level.M), ..fg_opts)
+        } else if prev_state.level == "E" {
+          draw.line((x_start, y_level.H), (x_start + x_slope, y_level.M))
+          draw.line((x_start, y_level.L), (x_start + x_slope, y_level.M))
+          draw.line((x_start + x_slope, y_level.M), (x_end, y_level.M), ..fg_opts)
         }
-      } else if event.type == "X" {
-        let opacity = 100% - (if "opacity" in event { event.opacity } else { 100% })
-        draw.line((x_start, y_m), (x_end, y_m), stroke: (paint: red.lighten(opacity)))
-      } else if event.type == "Z" {
-        let opacity = 100% - (if "opacity" in event { event.opacity } else { 100% })
-        draw.line((x_start, y_m), (x_end, y_m), stroke: (paint: blue.lighten(opacity)))
       } else if event.type == "D" or event.type == "U" {
-        let opacity = 100% - (if "opacity" in event { event.opacity } else { 100% })
-        let fg = (if "stroke" in event { event.stroke } else { black }).lighten(opacity)
+        let x_start = if ("X", "Z", "").contains(prev_state.type) { 0.0 } else { x_slope }
+        let x_end = event.len * w_scale + x_slope
         let fill = if event.type == "U" { gray } else if "fill" in event { event.fill.lighten(opacity) } else { none }
         let left-open = prev_state.level == ""
         let right-open = next_type == ""
         if left-open and right-open {
           if fill != none {
-            draw.rect((x_start, y_l), (x_end, y_h), stroke: none, fill: fill)
+            draw.rect((x_start, y_level.L), (x_end, y_level.H), stroke: none, fill: fill)
           }
-          draw.line((x_start, y_h), (x_end, y_h), stroke: (paint: fg))
-          draw.line((x_start, y_l), (x_end, y_l), stroke: (paint: fg))
+          draw.line((x_start, y_level.H), (x_end, y_level.H), ..fg_opts)
+          draw.line((x_start, y_level.L), (x_end, y_level.L), ..fg_opts)
         } else {
+          if prev_state.level == "H" or prev_state.level == "E" {
+            draw.line((0.0, y_level.H), (x_slope, y_level.M), ..fg_opts)
+          }
+          if prev_state.level == "L" or prev_state.level == "E" {
+            draw.line((0.0, y_level.L), (x_slope, y_level.M), ..fg_opts)
+          }
           let points = ()
           if left-open {
-            points.push((x_start, y_h))
-            points.push((x_end - x_slope, y_h))
-            points.push((x_end, y_m))
-            points.push((x_end - x_slope, y_l))
-            points.push((x_start, y_l))
+            points.push((x_start, y_level.H))
+            points.push((x_end - x_slope, y_level.H))
+            points.push((x_end, y_level.M))
+            points.push((x_end - x_slope, y_level.L))
+            points.push((x_start, y_level.L))
           } else if right-open {
-            points.push((x_end, y_h))
-            points.push((x_start + x_slope, y_h))
-            points.push((x_start, y_m))
-            points.push((x_start + x_slope, y_l))
-            points.push((x_end, y_l))
+            points.push((x_end, y_level.H))
+            points.push((x_start + x_slope, y_level.H))
+            points.push((x_start, y_level.M))
+            points.push((x_start + x_slope, y_level.L))
+            points.push((x_end, y_level.L))
           } else {
-            points.push((x_start, y_m))
-            points.push((x_start + x_slope, y_h))
-            points.push((x_end - x_slope, y_h))
-            points.push((x_end, y_m))
-            points.push((x_end - x_slope, y_l))
-            points.push((x_start + x_slope, y_l))
-            points.push((x_start, y_m))
+            points.push((x_start, y_level.M))
+            points.push((x_start + x_slope, y_level.H))
+            points.push((x_end - x_slope, y_level.H))
+            points.push((x_end, y_level.M))
+            points.push((x_end - x_slope, y_level.L))
+            points.push((x_start + x_slope, y_level.L))
+            points.push((x_start, y_level.M))
           }
-          draw.line(..points, stroke: (paint: fg), fill: fill)
+          draw.line(..points, ..fg_opts, fill: fill)
         }
-        draw.anchor("center", (event.len * w_scale / 2.0, y_m))
+        draw.anchor("center", ((x_end - x_start) / 2.0 + x_start, y_level.M))
         if "label" in event {
           draw.content("center", text(0.5em, fill: black.lighten(opacity), event.label))
         }
@@ -146,7 +155,7 @@
         for i in range(0, lanes.len()) {
           let lane = lanes.at(i)
           draw.group(ctx => {
-            draw.anchor("west", (0.0, y_l))
+            draw.anchor("west", (0.0, y_level.L))
             let prev_state = (level: "", type: "")
             for i in range(lane.wave.len()) {
               let event = lane.wave.at(i)
@@ -155,7 +164,7 @@
               prev_state.level = resolve_level(prev_state, event)
               prev_state.type = event.type
             }
-            draw.anchor("east", (0.0, y_h))
+            draw.anchor("east", (0.0, y_level.H))
             if grid {
               draw.on-layer(-1, {
                 draw.grid("west", "east", step: (x: 0.5 * w_scale, y: 0.5 * y_scale), stroke: (paint: gray.lighten(60%), thickness: 0.01em))
@@ -169,4 +178,3 @@
     })
   })
 }
-