diff --git a/.gitignore b/.gitignore
index e004695..e85e0b7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
+README.md.tinyenc
 secure-editor-go
 
 # ---> macOS
diff --git a/main.go b/main.go
index d145cb1..d09a180 100644
--- a/main.go
+++ b/main.go
@@ -4,13 +4,17 @@ import (
 	"crypto/aes"
 	"crypto/cipher"
 	"encoding/hex"
+	"encoding/json"
 	"fmt"
+	"image/color"
 	"os"
+	"path/filepath"
 
 	"fyne.io/fyne/v2"
 	"fyne.io/fyne/v2/app"
 	"fyne.io/fyne/v2/container"
 	"fyne.io/fyne/v2/dialog"
+	"fyne.io/fyne/v2/theme"
 	"fyne.io/fyne/v2/widget"
 )
 
@@ -18,6 +22,17 @@ const (
 	Version            = "0.1.1"
 	Title              = "Secure Editor"
 	AlgorithmAes256Gcm = "aes-256-gcm"
+
+	DefaultWindowWidth  = 800.0
+	DefaultWindowHeight = 600.0
+
+	ConfigFileName = "secure-editor-go-config.json"
+
+	// Exit codes:
+	//   0 -> file was saved and the editor exited
+	//   2 -> editor closed without saving
+	ExitCodeOK     = 0
+	ExitCodeNoSave = 2
 )
 
 func decrypt(ciphertext, key, nonce []byte) ([]byte, error) {
@@ -74,6 +89,93 @@ func isReadonly() bool {
 	return os.Getenv("READONLY") == "true"
 }
 
+// windowConfig is persisted to ~/.cache/secure-editor-go-config.json so the
+// editor remembers its window size across runs.
+type windowConfig struct {
+	Width  float32 `json:"width"`
+	Height float32 `json:"height"`
+}
+
+func configPath() (string, error) {
+	home, err := os.UserHomeDir()
+	if err != nil {
+		return "", err
+	}
+	return filepath.Join(home, ".cache", ConfigFileName), nil
+}
+
+func defaultConfig() windowConfig {
+	return windowConfig{Width: DefaultWindowWidth, Height: DefaultWindowHeight}
+}
+
+func loadConfig() windowConfig {
+	p, err := configPath()
+	if err != nil {
+		return defaultConfig()
+	}
+	data, err := os.ReadFile(p)
+	if err != nil {
+		return defaultConfig()
+	}
+	var c windowConfig
+	if err := json.Unmarshal(data, &c); err != nil {
+		return defaultConfig()
+	}
+	if c.Width <= 0 || c.Height <= 0 {
+		return defaultConfig()
+	}
+	return c
+}
+
+func saveConfig(size fyne.Size) {
+	p, err := configPath()
+	if err != nil {
+		return
+	}
+	if err := os.MkdirAll(filepath.Dir(p), 0755); err != nil {
+		return
+	}
+	c := windowConfig{Width: size.Width, Height: size.Height}
+	data, err := json.MarshalIndent(c, "", "  ")
+	if err != nil {
+		return
+	}
+	_ = os.WriteFile(p, data, 0644)
+}
+
+// clampToScreen shrinks size so it never exceeds the visible desktop area.
+// When the desktop size can't be determined it returns size unchanged.
+func clampToScreen(size fyne.Size) fyne.Size {
+	sw, sh := desktopSize()
+	if sw <= 0 || sh <= 0 {
+		return size
+	}
+	w, h := size.Width, size.Height
+	if w > sw {
+		w = sw
+	}
+	if h > sh {
+		h = sh
+	}
+	return fyne.NewSize(w, h)
+}
+
+// lightEditorTheme forces a light variant with a pure white input background
+// so the editable text area reads as a white editing surface regardless of
+// the system appearance setting. Readonly mode keeps the default theme (grey).
+type lightEditorTheme struct {
+	fyne.Theme
+}
+
+func (t *lightEditorTheme) Color(name fyne.ThemeColorName, _ fyne.ThemeVariant) color.Color {
+	if name == theme.ColorNameInputBackground {
+		return color.White
+	}
+	// Always resolve against the light variant so white input background
+	// stays paired with dark, readable text.
+	return t.Theme.Color(name, theme.VariantLight)
+}
+
 func main() {
 	args := os.Args
 	if len(args) == 2 && args[1] == "version" {
@@ -126,9 +228,19 @@ func main() {
 	isReadonly := isReadonly()
 
 	secureEditorApp := app.New()
+	if !isReadonly {
+		secureEditorApp.Settings().SetTheme(&lightEditorTheme{Theme: theme.DefaultTheme()})
+	}
 	window := secureEditorApp.NewWindow(Title)
-	window.Resize(fyne.NewSize(800, 600))
+
+	cfg := loadConfig()
+	window.Resize(clampToScreen(fyne.NewSize(cfg.Width, cfg.Height)))
+
+	// exitCode defaults to "closed without saving". The Save button raises
+	// it to ExitCodeOK. It is read after the event loop ends.
+	exitCode := ExitCodeNoSave
 	window.SetOnClosed(func() {
+		saveConfig(window.Canvas().Size())
 		secureEditorApp.Quit()
 	})
 
@@ -147,6 +259,7 @@ func main() {
 	}
 
 	exitButton := widget.NewButton(" [ Exit ] ", func() {
+		exitCode = ExitCodeNoSave
 		secureEditorApp.Quit()
 	})
 	saveButton := widget.NewButton(" [ Save ] ", func() {
@@ -161,6 +274,7 @@ func main() {
 			showErrorMessage(err, window)
 			return
 		}
+		exitCode = ExitCodeOK
 		secureEditorApp.Quit()
 	})
 
@@ -180,4 +294,6 @@ func main() {
 	window.SetContent(content)
 	window.CenterOnScreen()
 	window.ShowAndRun()
+
+	os.Exit(exitCode)
 }
diff --git a/screen_darwin.go b/screen_darwin.go
new file mode 100644
index 0000000..42478db
--- /dev/null
+++ b/screen_darwin.go
@@ -0,0 +1,32 @@
+//go:build darwin
+
+package main
+
+import (
+	"os/exec"
+	"strconv"
+	"strings"
+)
+
+// desktopSize returns the visible desktop size in points (device-independent
+// pixels), matching Fyne's coordinate system. It uses osascript instead of
+// cgo so the binary stays a plain Go build. Returns (0, 0) if it can't be
+// determined, in which case the caller skips clamping.
+func desktopSize() (float32, float32) {
+	// "bounds of window of desktop" -> "0, 0, W, H" in points.
+	out, err := exec.Command("osascript", "-e",
+		`tell application "Finder" to get bounds of window of desktop`).Output()
+	if err != nil {
+		return 0, 0
+	}
+	parts := strings.Split(strings.TrimSpace(string(out)), ", ")
+	if len(parts) < 4 {
+		return 0, 0
+	}
+	w, errW := strconv.ParseFloat(strings.TrimSpace(parts[2]), 32)
+	h, errH := strconv.ParseFloat(strings.TrimSpace(parts[3]), 32)
+	if errW != nil || errH != nil {
+		return 0, 0
+	}
+	return float32(w), float32(h)
+}
diff --git a/screen_other.go b/screen_other.go
new file mode 100644
index 0000000..e9e4937
--- /dev/null
+++ b/screen_other.go
@@ -0,0 +1,10 @@
+//go:build !darwin
+
+package main
+
+// desktopSize is a no-op fallback on non-darwin platforms where we don't have
+// a CGo-free way to query the screen. Returns (0, 0) so the caller skips
+// clamping and uses the saved/default size as-is.
+func desktopSize() (float32, float32) {
+	return 0, 0
+}