diff --git a/gameforui.go b/gameforui.go
index 76cff965a..15d8aaaf3 100644
--- a/gameforui.go
+++ b/gameforui.go
@@ -147,8 +147,8 @@ func (g *gameForUI) Layout(outsideWidth, outsideHeight float64) (float64, float6
 	return float64(sw), float64(sh)
 }
 
-func (g *gameForUI) UpdateInputState(inputState ui.InputState) {
-	theInputState.set(inputState)
+func (g *gameForUI) UpdateInputState(fn func(*ui.InputState)) {
+	fn(&theInputState.state)
 }
 
 func (g *gameForUI) Update() error {
diff --git a/input.go b/input.go
index 3119c4d09..3183679cb 100644
--- a/input.go
+++ b/input.go
@@ -405,7 +405,7 @@ func (i *inputState) set(inputState ui.InputState) {
 func (i *inputState) appendInputChars(runes []rune) []rune {
 	i.m.Lock()
 	defer i.m.Unlock()
-	return append(runes, i.state.Runes[:i.state.RunesCount]...)
+	return append(runes, i.state.Runes...)
 }
 
 func (i *inputState) isKeyPressed(key Key) bool {
@@ -453,9 +453,6 @@ func (i *inputState) appendTouchIDs(touches []TouchID) []TouchID {
 	defer i.m.Unlock()
 
 	for _, t := range i.state.Touches {
-		if !t.Valid {
-			continue
-		}
 		touches = append(touches, t.ID)
 	}
 	return touches
@@ -466,9 +463,6 @@ func (i *inputState) touchPosition(id TouchID) (int, int) {
 	defer i.m.Unlock()
 
 	for _, t := range i.state.Touches {
-		if !t.Valid {
-			continue
-		}
 		if id != t.ID {
 			continue
 		}
diff --git a/internal/ui/context.go b/internal/ui/context.go
index 54e1f40bc..773935d43 100644
--- a/internal/ui/context.go
+++ b/internal/ui/context.go
@@ -36,7 +36,7 @@ type Game interface {
 	NewOffscreenImage(width, height int) *Image
 	NewScreenImage(width, height int) *Image
 	Layout(outsideWidth, outsideHeight float64) (screenWidth, screenHeight float64)
-	UpdateInputState(InputState)
+	UpdateInputState(fn func(*InputState))
 	Update() error
 	DrawOffscreen() error
 	DrawFinalScreen(scale, offsetX, offsetY float64)
@@ -128,9 +128,9 @@ func (c *context) updateFrameImpl(graphicsDriver graphicsdriver.Graphics, update
 	// Update the game.
 	for i := 0; i < updateCount; i++ {
 		// Read the input state and use it for one tick to give a consistent result for one tick (#2496, #2501).
-		var inputState InputState
-		ui.readInputState(&inputState)
-		c.game.UpdateInputState(inputState)
+		c.game.UpdateInputState(func(inputState *InputState) {
+			ui.readInputState(inputState)
+		})
 
 		if err := hooks.RunBeforeUpdateHooks(); err != nil {
 			return err
diff --git a/internal/ui/input.go b/internal/ui/input.go
index a7a439323..ef76cd65f 100644
--- a/internal/ui/input.go
+++ b/internal/ui/input.go
@@ -32,10 +32,9 @@ const (
 type TouchID int
 
 type Touch struct {
-	Valid bool
-	ID    TouchID
-	X     int
-	Y     int
+	ID TouchID
+	X  int
+	Y  int
 }
 
 type InputState struct {
@@ -45,16 +44,28 @@ type InputState struct {
 	CursorY            int
 	WheelX             float64
 	WheelY             float64
-	Touches            [16]Touch
-	Runes              [16]rune
-	RunesCount         int
+	Touches            []Touch
+	Runes              []rune
 	WindowBeingClosed  bool
 }
 
-func (i *InputState) reset() {
+func (i *InputState) copyAndReset(dst *InputState) {
+	dst.KeyPressed = i.KeyPressed
+	dst.MouseButtonPressed = i.MouseButtonPressed
+	dst.CursorX = i.CursorX
+	dst.CursorY = i.CursorY
+	dst.WheelX = i.WheelX
+	dst.WheelY = i.WheelY
+	dst.Touches = append(dst.Touches[:0], i.Touches...)
+	dst.Runes = append(dst.Runes[:0], i.Runes...)
+	dst.WindowBeingClosed = i.WindowBeingClosed
+
+	// Reset the members that are updated by deltas, rather than absolute values.
 	i.WheelX = 0
 	i.WheelY = 0
-	i.RunesCount = 0
+	i.Runes = i.Runes[:0]
+
+	// Reset the member that is never reset until it is explicitly done.
 	i.WindowBeingClosed = false
 }
 
@@ -62,10 +73,5 @@ func (i *InputState) appendRune(r rune) {
 	if !unicode.IsPrint(r) {
 		return
 	}
-	if i.RunesCount >= len(i.Runes) {
-		return
-	}
-
-	i.Runes[i.RunesCount] = r
-	i.RunesCount++
+	i.Runes = append(i.Runes, r)
 }
diff --git a/internal/ui/input_js.go b/internal/ui/input_js.go
index 223e7b589..eee27a246 100644
--- a/internal/ui/input_js.go
+++ b/internal/ui/input_js.go
@@ -123,20 +123,17 @@ func (u *userInterfaceImpl) recoverCursorPosition() {
 }
 
 func (u *userInterfaceImpl) updateTouchesFromEvent(e js.Value) {
-	for i := range u.inputState.Touches {
-		u.inputState.Touches[i].Valid = false
-	}
+	u.inputState.Touches = u.inputState.Touches[:0]
 
 	touches := e.Get("targetTouches")
 	for i := 0; i < touches.Length(); i++ {
 		t := touches.Call("item", i)
 		x, y := u.context.clientPositionToLogicalPosition(t.Get("clientX").Float(), t.Get("clientY").Float(), u.DeviceScaleFactor())
-		u.inputState.Touches[i] = Touch{
-			Valid: true,
-			ID:    TouchID(t.Get("identifier").Int()),
-			X:     int(x),
-			Y:     int(y),
-		}
+		u.inputState.Touches = append(u.inputState.Touches, Touch{
+			ID: TouchID(t.Get("identifier").Int()),
+			X:  int(x),
+			Y:  int(y),
+		})
 	}
 }
 
diff --git a/internal/ui/input_mobile.go b/internal/ui/input_mobile.go
index e3126547f..6a92d4dd0 100644
--- a/internal/ui/input_mobile.go
+++ b/internal/ui/input_mobile.go
@@ -35,20 +35,16 @@ func (u *userInterfaceImpl) updateInputState(keys map[Key]struct{}, runes []rune
 		u.inputState.KeyPressed[k] = ok
 	}
 
-	copy(u.inputState.Runes[:], runes)
-	u.inputState.RunesCount = len(runes)
+	u.inputState.Runes = append(u.inputState.Runes, runes...)
 
-	for i := range u.inputState.Touches {
-		u.inputState.Touches[i].Valid = false
-	}
-	for i, t := range touches {
+	u.inputState.Touches = u.inputState.Touches[:0]
+	for _, t := range touches {
 		x, y := u.context.clientPositionToLogicalPosition(t.X, t.Y, u.DeviceScaleFactor())
-		u.inputState.Touches[i] = Touch{
-			Valid: true,
-			ID:    t.ID,
-			X:     int(x),
-			Y:     int(y),
-		}
+		u.inputState.Touches = append(u.inputState.Touches, Touch{
+			ID: t.ID,
+			X:  int(x),
+			Y:  int(y),
+		})
 	}
 }
 
diff --git a/internal/ui/input_nintendosdk.go b/internal/ui/input_nintendosdk.go
index 7c1824740..9e29e5967 100644
--- a/internal/ui/input_nintendosdk.go
+++ b/internal/ui/input_nintendosdk.go
@@ -38,17 +38,17 @@ func (u *userInterfaceImpl) updateInputState() {
 		C.ebitengine_GetTouches(&u.nativeTouches[0])
 	}
 
-	for i := range u.inputState.Touches {
-		u.inputState.Touches[i].Valid = false
-	}
-	for i, t := range u.nativeTouches {
+	u.m.Lock()
+	defer u.m.Unlock()
+
+	u.inputState.Touches = u.inputState.Touches[:0]
+	for _, t := range u.nativeTouches {
 		x, y := u.context.clientPositionToLogicalPosition(float64(t.x), float64(t.y), deviceScaleFactor)
-		u.inputState.Touches[i] = Touch{
-			Valid: true,
-			ID:    TouchID(t.id),
-			X:     int(x),
-			Y:     int(y),
-		}
+		u.inputState.Touches = append(u.inputState.Touches, Touch{
+			ID: TouchID(t.id),
+			X:  int(x),
+			Y:  int(y),
+		})
 	}
 }
 
diff --git a/internal/ui/ui_glfw.go b/internal/ui/ui_glfw.go
index 6c949b3b4..0d4e6fc7c 100644
--- a/internal/ui/ui_glfw.go
+++ b/internal/ui/ui_glfw.go
@@ -1341,8 +1341,7 @@ func monitorFromWindow(window *glfw.Window) *glfw.Monitor {
 func (u *userInterfaceImpl) readInputState(inputState *InputState) {
 	u.m.Lock()
 	defer u.m.Unlock()
-	*inputState = u.inputState
-	u.inputState.reset()
+	u.inputState.copyAndReset(inputState)
 }
 
 func (u *userInterfaceImpl) Window() Window {
diff --git a/internal/ui/ui_js.go b/internal/ui/ui_js.go
index 3291151df..76a635321 100644
--- a/internal/ui/ui_js.go
+++ b/internal/ui/ui_js.go
@@ -676,8 +676,7 @@ func (u *userInterfaceImpl) updateScreenSize() {
 }
 
 func (u *userInterfaceImpl) readInputState(inputState *InputState) {
-	*inputState = u.inputState
-	u.inputState.reset()
+	u.inputState.copyAndReset(inputState)
 	u.keyboardLayoutMap = js.Value{}
 }
 
diff --git a/internal/ui/ui_mobile.go b/internal/ui/ui_mobile.go
index 848f123d1..998c1cfa0 100644
--- a/internal/ui/ui_mobile.go
+++ b/internal/ui/ui_mobile.go
@@ -421,8 +421,7 @@ func (u *userInterfaceImpl) DeviceScaleFactor() float64 {
 func (u *userInterfaceImpl) readInputState(inputState *InputState) {
 	u.m.Lock()
 	defer u.m.Unlock()
-	*inputState = u.inputState
-	u.inputState.reset()
+	u.inputState.copyAndReset(inputState)
 }
 
 func (u *userInterfaceImpl) Window() Window {
diff --git a/internal/ui/ui_nintendosdk.go b/internal/ui/ui_nintendosdk.go
index 8528f6f06..0555ff94f 100644
--- a/internal/ui/ui_nintendosdk.go
+++ b/internal/ui/ui_nintendosdk.go
@@ -23,6 +23,7 @@ import "C"
 import (
 	stdcontext "context"
 	"runtime"
+	"sync"
 
 	"golang.org/x/sync/errgroup"
 
@@ -69,6 +70,8 @@ type userInterfaceImpl struct {
 
 	mainThread   *thread.OSThread
 	renderThread *thread.OSThread
+
+	m sync.Mutex
 }
 
 func (u *userInterfaceImpl) Run(game Game, options *RunOptions) error {
@@ -149,8 +152,9 @@ func (*userInterfaceImpl) ScreenSizeInFullscreen() (int, int) {
 }
 
 func (u *userInterfaceImpl) readInputState(inputState *InputState) {
-	*inputState = u.inputState
-	u.inputState.reset()
+	u.m.Lock()
+	defer u.m.Unlock()
+	u.inputState.copyAndReset(inputState)
 }
 
 func (*userInterfaceImpl) CursorMode() CursorMode {