diff --git a/.gitignore b/.gitignore
index 8ecdb7f..dd0d9fa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -122,3 +122,4 @@ docs/.*
 .vscode/tasks.json
 .vscode/launch.json
 devtools_options.yaml
+test/features/*_test.dart
diff --git a/build.yaml b/build.yaml
index 4c29746..0ecf930 100644
--- a/build.yaml
+++ b/build.yaml
@@ -6,6 +6,6 @@ targets:
       - lib/**
       - $package$
     builders:
-      pdf_signature|prune_unused_steps:
+      pdf_signature:
         generate_for:
           - test/features/**
diff --git a/test/features/app_preferences.feature b/test/features/app_preferences.feature
new file mode 100644
index 0000000..103c83a
--- /dev/null
+++ b/test/features/app_preferences.feature
@@ -0,0 +1,61 @@
+Feature: App preferences
+
+  As a user
+  I want to configure app preferences such as theme and language
+  So that the app matches my personal and regional needs, and remembers them next time
+
+  Scenario Outline: Choose a theme and apply it immediately
+    Given the settings screen is open
+    When the user selects the "<theme>" theme
+    Then the app UI updates to use the "<theme>" theme
+    And the preference {theme} is saved as {"<theme>"}
+
+    Examples:
+      | theme  |
+      | light  |
+      | dark   |
+      | system |
+
+  Scenario Outline: Choose a language and apply it immediately
+    Given the settings screen is open
+    When the user selects a supported language "<language>"
+    Then all visible texts are displayed in "<language>"
+    And the preference {language} is saved as {"<language>"}
+
+    Examples:
+      | language |
+      | en       |
+      | zh-TW    |
+      | es       |
+
+  Scenario Outline: Remember preferences across app restarts
+    Given the user previously set theme {"<theme>"} and language {"<language>"}
+    When the app launches
+    Then the app UI theme is {"<theme>"}
+    And the app language is {"<language>"}
+
+    Examples:
+      | theme  | language |
+      | dark   | en       |
+      | light  | zh-TW    |
+      | system | es       |
+
+  Scenario: Follow system appearance when theme is set to system
+    Given the user selects the "system" theme
+    And the OS appearance switches to dark mode
+    When the app is resumed or returns to foreground
+    Then the app UI updates to use the "dark" theme
+
+  Scenario: Reset preferences to defaults
+    Given the user has theme {"dark"} and language {"es"} saved
+    When the user taps "Reset to defaults"
+    Then the theme is set to {"system"}
+    And the language is set to the device locale
+    And both preferences are saved
+
+  Scenario: Ignore invalid stored values and fall back safely
+    Given stored preferences contain theme {"sepia"} and language {"xx"}
+    When the app launches
+    Then the theme falls back to {"system"}
+    And the language falls back to the device locale
+    And invalid values are replaced with valid defaults in storage
diff --git a/test/features/step/all_visible_texts_are_displayed_in.dart b/test/features/step/all_visible_texts_are_displayed_in.dart
new file mode 100644
index 0000000..92f9a47
--- /dev/null
+++ b/test/features/step/all_visible_texts_are_displayed_in.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: all visible texts are displayed in "<language>"
+Future<void> allVisibleTextsAreDisplayedIn(
+    WidgetTester tester, dynamic language) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/both_preferences_are_saved.dart b/test/features/step/both_preferences_are_saved.dart
new file mode 100644
index 0000000..cf6c1d5
--- /dev/null
+++ b/test/features/step/both_preferences_are_saved.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: both preferences are saved
+Future<void> bothPreferencesAreSaved(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/invalid_values_are_replaced_with_valid_defaults_in_storage.dart b/test/features/step/invalid_values_are_replaced_with_valid_defaults_in_storage.dart
new file mode 100644
index 0000000..5e8def0
--- /dev/null
+++ b/test/features/step/invalid_values_are_replaced_with_valid_defaults_in_storage.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: invalid values are replaced with valid defaults in storage
+Future<void> invalidValuesAreReplacedWithValidDefaultsInStorage(
+    WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/stored_preferences_contain_theme_and_language.dart b/test/features/step/stored_preferences_contain_theme_and_language.dart
new file mode 100644
index 0000000..64f1000
--- /dev/null
+++ b/test/features/step/stored_preferences_contain_theme_and_language.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: stored preferences contain theme {"sepia"} and language {"xx"}
+Future<void> storedPreferencesContainThemeAndLanguage(
+    WidgetTester tester, String param1, String param2) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_is_resumed_or_returns_to_foreground.dart b/test/features/step/the_app_is_resumed_or_returns_to_foreground.dart
new file mode 100644
index 0000000..2e12143
--- /dev/null
+++ b/test/features/step/the_app_is_resumed_or_returns_to_foreground.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app is resumed or returns to foreground
+Future<void> theAppIsResumedOrReturnsToForeground(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_language_is.dart b/test/features/step/the_app_language_is.dart
new file mode 100644
index 0000000..7f59382
--- /dev/null
+++ b/test/features/step/the_app_language_is.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app language is {"<language>"}
+Future<void> theAppLanguageIs(
+    WidgetTester tester, String param1, dynamic language) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_launches.dart b/test/features/step/the_app_launches.dart
new file mode 100644
index 0000000..99e5147
--- /dev/null
+++ b/test/features/step/the_app_launches.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app launches
+Future<void> theAppLaunches(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_ui_theme_is.dart b/test/features/step/the_app_ui_theme_is.dart
new file mode 100644
index 0000000..ea2a26e
--- /dev/null
+++ b/test/features/step/the_app_ui_theme_is.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app UI theme is {"<theme>"}
+Future<void> theAppUiThemeIs(
+    WidgetTester tester, String param1, dynamic theme) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_ui_updates_to_use_the_dark_theme.dart b/test/features/step/the_app_ui_updates_to_use_the_dark_theme.dart
new file mode 100644
index 0000000..0fac2b8
--- /dev/null
+++ b/test/features/step/the_app_ui_updates_to_use_the_dark_theme.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app UI updates to use the "dark" theme
+Future<void> theAppUiUpdatesToUseTheDarkTheme(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_app_ui_updates_to_use_the_theme.dart b/test/features/step/the_app_ui_updates_to_use_the_theme.dart
new file mode 100644
index 0000000..7396f98
--- /dev/null
+++ b/test/features/step/the_app_ui_updates_to_use_the_theme.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the app UI updates to use the "<theme>" theme
+Future<void> theAppUiUpdatesToUseTheTheme(
+    WidgetTester tester, dynamic theme) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_language_falls_back_to_the_device_locale.dart b/test/features/step/the_language_falls_back_to_the_device_locale.dart
new file mode 100644
index 0000000..40abade
--- /dev/null
+++ b/test/features/step/the_language_falls_back_to_the_device_locale.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the language falls back to the device locale
+Future<void> theLanguageFallsBackToTheDeviceLocale(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_language_is_set_to_the_device_locale.dart b/test/features/step/the_language_is_set_to_the_device_locale.dart
new file mode 100644
index 0000000..6f4977a
--- /dev/null
+++ b/test/features/step/the_language_is_set_to_the_device_locale.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the language is set to the device locale
+Future<void> theLanguageIsSetToTheDeviceLocale(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_os_appearance_switches_to_dark_mode.dart b/test/features/step/the_os_appearance_switches_to_dark_mode.dart
new file mode 100644
index 0000000..c367885
--- /dev/null
+++ b/test/features/step/the_os_appearance_switches_to_dark_mode.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the OS appearance switches to dark mode
+Future<void> theOsAppearanceSwitchesToDarkMode(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_preference_is_saved_as.dart b/test/features/step/the_preference_is_saved_as.dart
new file mode 100644
index 0000000..fa0133c
--- /dev/null
+++ b/test/features/step/the_preference_is_saved_as.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the preference {language} is saved as {"<language>"}
+Future<void> thePreferenceIsSavedAs(WidgetTester tester, dynamic param1,
+    String param2, dynamic language) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_settings_screen_is_open.dart b/test/features/step/the_settings_screen_is_open.dart
new file mode 100644
index 0000000..6f6d0bd
--- /dev/null
+++ b/test/features/step/the_settings_screen_is_open.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the settings screen is open
+Future<void> theSettingsScreenIsOpen(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_theme_falls_back_to.dart b/test/features/step/the_theme_falls_back_to.dart
new file mode 100644
index 0000000..eeb9b46
--- /dev/null
+++ b/test/features/step/the_theme_falls_back_to.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the theme falls back to {"system"}
+Future<void> theThemeFallsBackTo(WidgetTester tester, String param1) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_theme_is_set_to.dart b/test/features/step/the_theme_is_set_to.dart
new file mode 100644
index 0000000..3608b12
--- /dev/null
+++ b/test/features/step/the_theme_is_set_to.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the theme is set to {"system"}
+Future<void> theThemeIsSetTo(WidgetTester tester, String param1) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_has_theme_and_language_saved.dart b/test/features/step/the_user_has_theme_and_language_saved.dart
new file mode 100644
index 0000000..185e035
--- /dev/null
+++ b/test/features/step/the_user_has_theme_and_language_saved.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user has theme {"dark"} and language {"es"} saved
+Future<void> theUserHasThemeAndLanguageSaved(
+    WidgetTester tester, String param1, String param2) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_previously_set_theme_and_language.dart b/test/features/step/the_user_previously_set_theme_and_language.dart
new file mode 100644
index 0000000..f28337c
--- /dev/null
+++ b/test/features/step/the_user_previously_set_theme_and_language.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user previously set theme {"<theme>"} and language {"<language>"}
+Future<void> theUserPreviouslySetThemeAndLanguage(WidgetTester tester,
+    String param1, String param2, dynamic theme, dynamic language) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_selects_a_supported_language.dart b/test/features/step/the_user_selects_a_supported_language.dart
new file mode 100644
index 0000000..0778de0
--- /dev/null
+++ b/test/features/step/the_user_selects_a_supported_language.dart
@@ -0,0 +1,7 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user selects a supported language "<language>"
+Future<void> theUserSelectsASupportedLanguage(
+    WidgetTester tester, dynamic language) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_selects_the_system_theme.dart b/test/features/step/the_user_selects_the_system_theme.dart
new file mode 100644
index 0000000..433afdb
--- /dev/null
+++ b/test/features/step/the_user_selects_the_system_theme.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user selects the "system" theme
+Future<void> theUserSelectsTheSystemTheme(WidgetTester tester) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_selects_the_theme.dart b/test/features/step/the_user_selects_the_theme.dart
new file mode 100644
index 0000000..342f7d9
--- /dev/null
+++ b/test/features/step/the_user_selects_the_theme.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user selects the "<theme>" theme
+Future<void> theUserSelectsTheTheme(WidgetTester tester, dynamic theme) async {
+  throw UnimplementedError();
+}
diff --git a/test/features/step/the_user_taps_reset_to_defaults.dart b/test/features/step/the_user_taps_reset_to_defaults.dart
new file mode 100644
index 0000000..29bf9a8
--- /dev/null
+++ b/test/features/step/the_user_taps_reset_to_defaults.dart
@@ -0,0 +1,6 @@
+import 'package:flutter_test/flutter_test.dart';
+
+/// Usage: the user taps "Reset to defaults"
+Future<void> theUserTapsResetToDefaults(WidgetTester tester) async {
+  throw UnimplementedError();
+}