diff --git a/go.mod b/go.mod
index 0498488..a7218c9 100644
--- a/go.mod
+++ b/go.mod
@@ -1,8 +1,11 @@
 module git.tebibyte.media/tomo/backend
 
-go 1.20
+go 1.21.0
+
+toolchain go1.22.2
 
 require (
+	git.tebibyte.media/sashakoshka/goutil v0.3.0
 	git.tebibyte.media/tomo/tomo v0.46.1
 	git.tebibyte.media/tomo/typeset v0.8.0
 	git.tebibyte.media/tomo/xgbkb v1.0.1
diff --git a/go.sum b/go.sum
index b92a944..12341ad 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+git.tebibyte.media/sashakoshka/goutil v0.3.0 h1:dcZ/9/or7m8eTpf2B1Pu4CscplXh2INTXFartz+ExwE=
+git.tebibyte.media/sashakoshka/goutil v0.3.0/go.mod h1:e1OXLa+wX7x/F8n8gyxz2hnfVCEkWzGrZNX8/k/lR/M=
 git.tebibyte.media/sashakoshka/xgbkb v1.0.0/go.mod h1:pNcE6TRO93vHd6q42SdwLSTTj25L0Yzggz7yLe0JV6Q=
 git.tebibyte.media/tomo/tomo v0.46.1 h1:/8fT6I9l4TK529zokrThbNDHGRvUsNgif1Zs++0PBSQ=
 git.tebibyte.media/tomo/tomo v0.46.1/go.mod h1:WrtilgKB1y8O2Yu7X4mYcRiqOlPR8NuUnoA/ynkQWrs=
diff --git a/internal/system/attribute.go b/internal/system/attribute.go
index aacab29..b583bcc 100644
--- a/internal/system/attribute.go
+++ b/internal/system/attribute.go
@@ -1,12 +1,12 @@
 package system
 
 import "git.tebibyte.media/tomo/tomo"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 type attrHierarchy [T tomo.Attr] struct {
 	fallback T
-	style    util.Optional[T]
-	user     util.Optional[T]
+	style    ucontainer.Optional[T]
+	user     ucontainer.Optional[T]
 }
 
 func (this *attrHierarchy[T]) SetFallback (fallback T) {
diff --git a/internal/system/box.go b/internal/system/box.go
index 224e9ac..dfe6740 100644
--- a/internal/system/box.go
+++ b/internal/system/box.go
@@ -7,20 +7,21 @@ import "git.tebibyte.media/tomo/tomo/data"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
+import "git.tebibyte.media/sashakoshka/goutil/image/color"
 
 type box struct {
 	system *System
 	parent parent
 	outer  anyBox
 
-	tags             util.Set[string]
+	tags             ucontainer.Set[string]
 	role             tomo.Role
 	lastStyleNonce   int
 	lastIconSetNonce int
 	styleApplicator  *styleApplicator
 
-	minSize             util.Memo[image.Point]
+	minSize             ucontainer.Memo[image.Point]
 	bounds              image.Rectangle
 	innerClippingBounds image.Rectangle
 	
@@ -41,7 +42,7 @@ type box struct {
 	focused bool
 	pressed bool
 	
-	canvas util.Memo[canvas.Canvas]
+	canvas ucontainer.Memo[canvas.Canvas]
 	drawer canvas.Drawer
 
 	on struct {
@@ -68,10 +69,10 @@ func (this *System) newBox (outer anyBox) *box {
 		system:  this,
 		outer:   outer,
 		drawer:  outer,
-		tags:    make(util.Set[string]),
+		tags:    make(ucontainer.Set[string]),
 	}
 	box.attrColor.SetFallback(tomo.AColor(color.Transparent))
-	box.canvas = util.NewMemo (func () canvas.Canvas {
+	box.canvas = ucontainer.NewMemo (func () canvas.Canvas {
 		if box.parent == nil { return nil }
 		parentCanvas := box.parent.getCanvas()
 		if parentCanvas == nil { return nil }
@@ -82,7 +83,7 @@ func (this *System) newBox (outer anyBox) *box {
 		box.drawer = box
 		box.outer  = box
 	}
-	box.minSize = util.NewMemo(box.calculateMinimumSize)
+	box.minSize = ucontainer.NewMemo(box.calculateMinimumSize)
 	return box
 }
 
@@ -476,7 +477,7 @@ func (this *box) drawBorders (can canvas.Canvas) {
 	rectangle := func (x0, y0, x1, y1 int, c color.Color) {
 		area := image.Rect(x0, y0, x1, y1)
 		if area.Empty() { return }
-		if util.Transparent(c) && this.parent != nil {
+		if ucolor.Transparent(c) && this.parent != nil {
 			this.parent.drawBackgroundPart(can.SubCanvas(area))
 		}
 		pen.Fill(c)
@@ -682,7 +683,7 @@ func (this *box) transparent () bool {
 	// TODO uncomment once we have
 	// a way to detect texture transparency
 	col := this.attrColor.Value().Color
-	return col == nil || util.Transparent(col) /*&&
+	return col == nil || ucolor.Transparent(col) /*&&
 		(this.texture == nil || !this.texture.Opaque())*/
 }
 
diff --git a/internal/system/containerbox.go b/internal/system/containerbox.go
index 58a3ef7..b821df5 100644
--- a/internal/system/containerbox.go
+++ b/internal/system/containerbox.go
@@ -1,11 +1,11 @@
 package system
 
 import "image"
+import "slices"
 import "image/color"
 import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
-import "git.tebibyte.media/tomo/backend/internal/util"
 
 type containerBox struct {
 	*box
@@ -50,7 +50,7 @@ func (this *containerBox) OnContentBoundsChange (callback func()) event.Cookie {
 
 func (this *containerBox) Add (child tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	if util.IndexOf(this.children, box) > -1 { return }
+	if slices.Index(this.children, box) > -1 { return }
 
 	box.setParent(this)
 	box.flushActionQueue()
@@ -61,26 +61,26 @@ func (this *containerBox) Add (child tomo.Object) {
 
 func (this *containerBox) Remove (child tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	index := util.IndexOf(this.children, box)
+	index := slices.Index(this.children, box)
 	if index < 0 { return }
 
 	box.setParent(nil)
-	this.children = util.Remove(this.children, index)
+	this.children = slices.Delete(this.children, index, index)
 	this.invalidateLayout()
 	this.invalidateMinimum()
 }
 
 func (this *containerBox) Insert (child, before tomo.Object) {
 	box := assertAnyBox(child.GetBox())
-	if util.IndexOf(this.children, box) > -1 { return }
+	if slices.Index(this.children, box) > -1 { return }
 
 	beforeBox := assertAnyBox(before.GetBox())
-	index     := util.IndexOf(this.children, beforeBox)
+	index     := slices.Index(this.children, beforeBox)
 	
 	if index < 0 {
 		this.children = append(this.children, box)
 	} else {
-		this.children = util.Insert(this.children, index, box)
+		this.children = slices.Insert(this.children, index, box)
 	}
 	box.setParent(this)
 
diff --git a/internal/system/hierarchy.go b/internal/system/hierarchy.go
index 5a45116..a3e05a5 100644
--- a/internal/system/hierarchy.go
+++ b/internal/system/hierarchy.go
@@ -5,7 +5,7 @@ import "git.tebibyte.media/tomo/tomo"
 import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/canvas"
 import "git.tebibyte.media/tomo/backend/style"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // Hierarchy is coupled to a tomo.Window implementation, and manages a tree of
 // Boxes.
@@ -25,9 +25,9 @@ type Hierarchy struct {
 	drags         [10][]anyBox
 	minimumSize   image.Point
 
-	needStyle    util.Set[anyBox]
-	needLayout   util.Set[anyBox]
-	needDraw     util.Set[anyBox]
+	needStyle    ucontainer.Set[anyBox]
+	needLayout   ucontainer.Set[anyBox]
+	needDraw     ucontainer.Set[anyBox]
 	needRedo     bool
 	minimumClean bool
 }
@@ -53,9 +53,9 @@ func (this *System) NewHierarchy (link WindowLink) *Hierarchy {
 	hierarchy := &Hierarchy {
 		system:      this,
 		link:        link,
-		needStyle:   make(util.Set[anyBox]),
-		needLayout:  make(util.Set[anyBox]),
-		needDraw:    make(util.Set[anyBox]),
+		needStyle:   make(ucontainer.Set[anyBox]),
+		needLayout:  make(ucontainer.Set[anyBox]),
+		needDraw:    make(ucontainer.Set[anyBox]),
 	}
 	this.hierarchies.Add(hierarchy)
 	return hierarchy
diff --git a/internal/system/system.go b/internal/system/system.go
index 0ea9bb9..9e9da1d 100644
--- a/internal/system/system.go
+++ b/internal/system/system.go
@@ -4,7 +4,7 @@ import "io"
 import "image"
 import "git.tebibyte.media/tomo/tomo/canvas"
 import "git.tebibyte.media/tomo/backend/style"
-import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 // System is coupled to a tomo.Backend implementation, and manages Hierarchies
 // and Boxes.
@@ -17,7 +17,7 @@ type System struct {
 	styleNonce   int
 	iconSetNonce int
 	
-	hierarchies util.Set[*Hierarchy]
+	hierarchies ucontainer.Set[*Hierarchy]
 }
 
 // BackendLink allows the System to call up into the tomo.Backend implementation
@@ -41,7 +41,7 @@ type SurfaceLink interface {
 func New (link BackendLink) *System {
 	return &System {
 		link:        link,
-		hierarchies: make(util.Set[*Hierarchy]),
+		hierarchies: make(ucontainer.Set[*Hierarchy]),
 	}
 }
 
diff --git a/internal/system/textbox.go b/internal/system/textbox.go
index 1093093..67318a0 100644
--- a/internal/system/textbox.go
+++ b/internal/system/textbox.go
@@ -12,6 +12,7 @@ import "git.tebibyte.media/tomo/tomo/input"
 import "git.tebibyte.media/tomo/tomo/event"
 import "git.tebibyte.media/tomo/tomo/canvas"
 import "git.tebibyte.media/tomo/backend/internal/util"
+import "git.tebibyte.media/sashakoshka/goutil/container"
 
 type textBox struct {
 	*box
@@ -36,7 +37,7 @@ type textBox struct {
 
 	drawer     typeset.Drawer
 	face       util.Cycler[font.Face]
-	lineHeight util.Memo[fixed.Int26_6]
+	lineHeight ucontainer.Memo[fixed.Int26_6]
 
 	on struct {
 		contentBoundsChange event.FuncBroadcaster
@@ -49,7 +50,7 @@ func (this *System) NewTextBox () tomo.TextBox {
 	box.box = this.newBox(box)
 	box.attrTextColor.SetFallback(tomo.ATextColor(color.Black))
 	box.attrDotColor.SetFallback(tomo.ADotColor(color.RGBA { G: 255, B: 255, A: 255}))
-	box.lineHeight = util.NewMemo(func () fixed.Int26_6 {
+	box.lineHeight = ucontainer.NewMemo(func () fixed.Int26_6 {
 		face := box.face.Value()
 		if face == nil { return 0 }
 		metrics := face.Metrics()
diff --git a/internal/util/util.go b/internal/util/util.go
index a13ac27..a222e80 100644
--- a/internal/util/util.go
+++ b/internal/util/util.go
@@ -1,100 +1,6 @@
 package util
 
 import "io"
-import "image/color"
-
-// IndexOf returns the index of needle within haystack. If needle does not exist
-// within haystack, it returns -1.
-func IndexOf[T comparable] (haystack []T, needle T) int {
-	for index, test := range haystack {
-		if test == needle {
-			return index
-		}
-	}
-	return -1
-}
-
-// Remove removes an element from slice at index.
-func Remove[T any] (slice []T, index int) []T {
-	return append(slice[:index], slice[index + 1:]...)
-}
-
-// Insert inserts an element into slice at index.
-func Insert[T any] (slice []T, index int, element T) []T {
-	slice = append(slice[:index + 1], slice[index:]...)
-	slice[index] = element
-	return slice
-}
-
-// Transparent returns whether or not a color has transparency.
-func Transparent (c color.Color) bool {
-	_, _, _, a := c.RGBA()
-	return a != 0xFFFF
-}
-
-// Set is a set of unique items, built on top of map.
-type Set[T comparable] map[T] struct { }
-
-// Empty returns true if there are no items in the set.
-func (set Set[T]) Empty () bool {
-	return set == nil || len(set) == 0
-}
-
-// Has returns true if the set contains item.
-func (set Set[T]) Has (item T) bool {
-	if set == nil {
-		return false
-	}
-	_, ok := set[item]
-	return ok
-}
-
-// Add adds an item to the set.
-func (set Set[T]) Add (item T) {
-	set[item] = struct { } { }
-}
-
-// Pop removes the first accessible item from the set and returns it.
-func (set Set[T]) Pop () (item T) {
-	for item := range set {
-		delete(set, item)
-		return item
-	}
-	return
-}
-
-// Memo holds a cached value.
-type Memo[T any] struct {
-	cache  T
-	valid  bool
-	update func () T
-}
-
-// NewMemo creates a new Memo which will take its value from the specified
-// update callback.
-func NewMemo[T any] (update func () T) Memo[T] {
-	return Memo[T] {
-		update: update,
-	}
-}
-
-// Value returns the Memo's value, updating it if the current cached value is
-// invalid.
-func (this *Memo[T]) Value () T {
-	if !this.valid {
-		this.cache = this.update()
-		this.valid = true
-	}
-	return this.cache
-}
-
-// Invalidate marks the Memo's value as invalid, which will cause it to be
-// updated the next time Value is called.
-func (this *Memo[T]) Invalidate () {
-	var zero T
-	this.cache = zero
-	this.valid = false
-}
 
 // Cycler stores a value and an accompanying io.Closer. When the value is set,
 // the closer associated with the previous value is closed.
@@ -124,33 +30,3 @@ func (this *Cycler[T]) Close () error {
 	this.closer = nil
 	return err
 }
-
-// Optional is an optional value.
-type Optional[T any] struct {
-	value T
-	exists bool
-}
-
-// Value returns the value and true if the value exists. If not, it returns the
-// last set value and false.
-func (this *Optional[T]) Value () (T, bool) {
-	return this.value, this.exists
-}
-
-// Set sets the value.
-func (this *Optional[T]) Set (value T) {
-	this.value = value
-	this.exists = true
-}
-
-// Unset unsets the value.
-func (this *Optional[T]) Unset () {
-	var zero T
-	this.value = zero
-	this.exists = false
-}
-
-// Exists returns if the value is currently set.
-func (this *Optional[T]) Exists () bool {
-	return this.exists
-}