diff --git a/src/main/java/de/extio/game_engine/module/AbstractClientModule.java b/src/main/java/de/extio/game_engine/module/AbstractClientModule.java
new file mode 100644
index 0000000..0895968
--- /dev/null
+++ b/src/main/java/de/extio/game_engine/module/AbstractClientModule.java
@@ -0,0 +1,42 @@
+package de.extio.game_engine.module;
+
+/**
+ * Root of all UI client modules
+ */
+public abstract class AbstractClientModule extends AbstractModule {
+	
+	final static int MODULE_PRIORITY_LOW = 25;
+	
+	final static int MODULE_PRIORITY_NORMAL = 50;
+	
+	final static int MODULE_PRIORITY_HIGH = 75;
+	
+	public AbstractClientModule() {
+		
+	}
+	
+	public int getPriority() {
+		return MODULE_PRIORITY_NORMAL;
+	}
+	
+	public boolean isAlwaysDisplay() {
+		return false;
+	}
+	
+	public void onShow() {
+		
+	}
+	
+	public void onHide() {
+		
+	}
+	
+	public void runUiPreEvents() {
+		
+	}
+	
+	public void runUiPostEvents() {
+		
+	}
+	
+}
diff --git a/src/main/java/de/extio/game_engine/module/AbstractModule.java b/src/main/java/de/extio/game_engine/module/AbstractModule.java
new file mode 100644
index 0000000..0964a09
--- /dev/null
+++ b/src/main/java/de/extio/game_engine/module/AbstractModule.java
@@ -0,0 +1,43 @@
+package de.extio.game_engine.module;
+
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+/**
+ * Root of all modules
+ */
+public abstract class AbstractModule {
+	
+	protected static final Logger LOGGER = LoggerFactory.getLogger(AbstractModule.class);
+	
+	public AbstractModule() {
+		
+	}
+
+	public void onLoad() {
+		
+	}
+	
+	public void onUnload() {
+		
+	}
+	
+	public void onActivate() {
+		
+	}
+	
+	public void onDeactivate() {
+		
+	}
+	
+	
+	public void run() {
+		
+	}
+
+	@Override
+	public String toString() {
+		return this.getClass().getSimpleName();
+	}
+	
+}
diff --git a/src/main/java/de/extio/game_engine/module/ModuleManager.java b/src/main/java/de/extio/game_engine/module/ModuleManager.java
new file mode 100644
index 0000000..73ce36d
--- /dev/null
+++ b/src/main/java/de/extio/game_engine/module/ModuleManager.java
@@ -0,0 +1,41 @@
+package de.extio.game_engine.module;
+
+import java.util.List;
+
+public interface ModuleManager {
+	
+	void loadModule(Class<? extends AbstractModule> clazz);
+	
+	void unloadModule(Class<? extends AbstractModule> clazz);
+	
+	List<AbstractModule> getModulesAll();
+	
+	List<AbstractModule> getModulesActive();
+	
+	List<AbstractClientModule> getModulesActiveClientModules();
+	
+	List<AbstractClientModule> getModulesDisplayedClientModules();
+	
+	void changeActiveState(String className, boolean active);
+	
+	void changeActiveState(Class<? extends AbstractModule> clazz, boolean active);
+	
+	void deactivateAll();
+	
+	void changeDisplayState(String className, boolean active);
+	
+	void changeDisplayState(Class<? extends AbstractClientModule> clazz, boolean display);
+	
+	boolean isDisplayed(String className);
+	
+	boolean isDisplayed(Class<? extends AbstractClientModule> clazz);
+	
+	void hideAll();
+	
+	void hideExcept(String... classNames);
+	
+	void restoreVisibility();
+	
+	boolean isModal();
+	
+}
diff --git a/src/main/java/de/extio/game_engine/module/ModuleManagerAutoConfiguration.java b/src/main/java/de/extio/game_engine/module/ModuleManagerAutoConfiguration.java
new file mode 100644
index 0000000..b89599e
--- /dev/null
+++ b/src/main/java/de/extio/game_engine/module/ModuleManagerAutoConfiguration.java
@@ -0,0 +1,18 @@
+package de.extio.game_engine.module;
+
+import java.util.List;
+
+import org.springframework.boot.autoconfigure.AutoConfiguration;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
+import org.springframework.context.annotation.Bean;
+
+@AutoConfiguration
+@ConditionalOnProperty(name = "game-engine.module.enabled", havingValue = "true", matchIfMissing = true)
+public class ModuleManagerAutoConfiguration {
+
+	@Bean
+	ModuleManager moduleManager(final List<AbstractModule> initialModules) {
+		return new ModuleManagerImpl(initialModules);
+	}
+
+}
diff --git a/src/main/java/de/extio/game_engine/module/ModuleManagerImpl.java b/src/main/java/de/extio/game_engine/module/ModuleManagerImpl.java
new file mode 100644
index 0000000..5ea9973
--- /dev/null
+++ b/src/main/java/de/extio/game_engine/module/ModuleManagerImpl.java
@@ -0,0 +1,297 @@
+package de.extio.game_engine.module;
+
+import java.util.ArrayDeque;
+import java.util.ArrayList;
+import java.util.Deque;
+import java.util.List;
+import java.util.function.Consumer;
+
+import org.apache.logging.log4j.LogManager;
+import org.apache.logging.log4j.Logger;
+import org.springframework.beans.factory.InitializingBean;
+
+public class ModuleManagerImpl implements InitializingBean, ModuleManager {
+	
+	private static final Logger LOGGER = LogManager.getLogger();
+	
+	private final List<AbstractModule> modulesInitial;
+	
+	private final List<AbstractModule> modulesAll = new ArrayList<>();
+	
+	private List<AbstractModule> modulesAllView = List.of();
+	
+	private List<AbstractModule> modulesActiveView = List.of();
+	
+	private List<AbstractClientModule> modulesActiveClientModulesView = List.of();
+	
+	private List<AbstractClientModule> modulesDisplayedClientModulesView = List.of();
+	
+	private final List<AbstractModule> modulesActive = new ArrayList<>();
+	
+	private final List<AbstractClientModule> modulesDisplayed = new ArrayList<>();
+	
+	private final Deque<List<AbstractClientModule>> lastVisibleStates = new ArrayDeque<>();
+	
+	public ModuleManagerImpl(final List<AbstractModule> initialModules) {
+		this.modulesInitial = initialModules;
+	}
+	
+	@Override
+	public void afterPropertiesSet() throws Exception {
+		if (this.modulesInitial == null || this.modulesInitial.isEmpty()) {
+			return;
+		}
+		this.modulesInitial.forEach(module -> this.invokeSafe(module, AbstractModule::onLoad));
+		this.modulesAll.addAll(this.modulesInitial);
+		this.sortModules(this.modulesAll);
+		this.modulesAllView = List.copyOf(this.modulesAll);
+		this.modulesInitial.clear();
+	}
+	
+	@Override
+	public List<AbstractModule> getModulesAll() {
+		return this.modulesAllView;
+	}
+	
+	@Override
+	public List<AbstractModule> getModulesActive() {
+		return this.modulesActiveView;
+	}
+	
+	@Override
+	public List<AbstractClientModule> getModulesActiveClientModules() {
+		return this.modulesActiveClientModulesView;
+	}
+	
+	@Override
+	public List<AbstractClientModule> getModulesDisplayedClientModules() {
+		return modulesDisplayedClientModulesView;
+	}
+	
+	@Override
+	public void loadModule(final Class<? extends AbstractModule> clazz) {
+		if (this.modulesAll.stream().anyMatch(module -> clazz.isInstance(module))) {
+			LOGGER.debug("AbstractModule already loaded: " + clazz.getName());
+			return;
+		}
+		
+		LOGGER.debug("Loading module " + clazz.getName());
+		
+		try {
+			final AbstractModule module = AbstractModule.class.cast(clazz.getDeclaredConstructor().newInstance());
+			this.invokeSafe(module, m -> m.onLoad());
+			this.modulesAll.add(module);
+			this.sortModules(this.modulesAll);
+			this.modulesAllView = List.copyOf(this.modulesAll);
+		}
+		catch (final Exception e) {
+			LOGGER.error("Error loading module " + clazz.getName(), e);
+		}
+	}
+	
+	@Override
+	public void unloadModule(final Class<? extends AbstractModule> clazz) {
+		try {
+			final AbstractModule module = this.modulesAll.stream().filter(mod -> clazz.isInstance(mod)).findAny().orElse(null);
+			
+			if (module == null) {
+				LOGGER.debug("AbstractModule not loaded: " + clazz.getName());
+				return;
+			}
+			
+			this.changeActiveState(clazz, false);
+			this.modulesAll.remove(module);
+			this.sortModules(this.modulesAll);
+			this.modulesAllView = List.copyOf(this.modulesAll);
+			
+			this.invokeSafe(module, m -> m.onUnload());
+			
+			LOGGER.debug("Unloaded module " + clazz.getName());
+		}
+		catch (final Exception e) {
+			LOGGER.error("Error unloading module " + clazz.getName(), e);
+		}
+	}
+	
+	@Override
+	public void changeActiveState(final String className, final boolean active) {
+		try {
+			final var clazz = Class.forName(className);
+			this.changeActiveState(clazz.asSubclass(AbstractModule.class), active);
+		}
+		catch (final ClassNotFoundException e) {
+			LOGGER.error("Class not found: " + className, e);
+		}
+	}
+	
+	@Override
+	public void changeActiveState(final Class<? extends AbstractModule> clazz, final boolean active) {
+		this.modulesActiveView.stream()
+				.filter(module -> clazz.isAssignableFrom(module.getClass()))
+				.findAny()
+				.ifPresentOrElse(module -> {
+					if (!active) {
+						if (module instanceof final AbstractClientModule clientModule) {
+							this.changeDisplayState(clientModule.getClass(), false);
+						}
+						this.invokeSafe(module, AbstractModule::onDeactivate);
+						this.modulesActive.remove(module);
+						this.sortModules(this.modulesActive);
+						this.modulesActiveView = List.copyOf(this.modulesActive);
+						this.modulesActiveClientModulesView = this.modulesActive.stream()
+								.filter(m -> m instanceof AbstractClientModule)
+								.map(m -> (AbstractClientModule) m)
+								.toList();
+						this.modulesDisplayedClientModulesView = List.copyOf(this.modulesDisplayed);
+						
+						LOGGER.debug("Deactivated " + clazz.getName());
+					}
+				}, () -> {
+					if (active) {
+						this.modulesAll.stream()
+								.filter(module -> clazz.isAssignableFrom(module.getClass()))
+								.findFirst()
+								.ifPresent(module -> {
+									this.invokeSafe(module, AbstractModule::onActivate);
+									if (module instanceof final AbstractClientModule clientModule && clientModule.isAlwaysDisplay()) {
+										this.changeDisplayState(clientModule.getClass(), true);
+									}
+									this.modulesActive.add(module);
+									this.sortModules(this.modulesActive);
+									this.modulesActiveView = List.copyOf(this.modulesActive);
+									this.modulesActiveClientModulesView = this.modulesActive.stream()
+											.filter(m -> m instanceof AbstractClientModule)
+											.map(m -> (AbstractClientModule) m)
+											.toList();
+									this.modulesDisplayedClientModulesView = List.copyOf(this.modulesDisplayed);
+									
+									LOGGER.debug("Activated " + clazz.getName());
+								});
+					}
+				});
+	}
+	
+	@Override
+	public void deactivateAll() {
+		for (final AbstractModule module : this.modulesActiveView) {
+			this.changeActiveState(module.getClass(), false);
+		}
+		this.lastVisibleStates.clear();
+	}
+	
+	@Override
+	public void changeDisplayState(final String className, final boolean active) {
+		try {
+			final var clazz = Class.forName(className);
+			this.changeDisplayState(clazz.asSubclass(AbstractClientModule.class), active);
+		}
+		catch (final ClassNotFoundException e) {
+			LOGGER.error("Class not found: " + className, e);
+		}
+	}
+	
+	@Override
+	public void changeDisplayState(final Class<? extends AbstractClientModule> clazz, final boolean display) {
+		for (final var module : this.modulesAll) {
+			if (module instanceof final AbstractClientModule clientModule && clazz.isAssignableFrom(module.getClass())) {
+				final boolean curDisplayed = this.modulesDisplayed.stream().anyMatch(mod -> clazz.isAssignableFrom(mod.getClass()));
+				
+				final boolean doDisplay = display || clientModule.isAlwaysDisplay();
+				if (doDisplay && !curDisplayed) {
+					this.modulesDisplayed.add(clientModule);
+					this.invokeSafe(clientModule, m -> ((AbstractClientModule) m).onShow());
+				}
+				else if (!doDisplay && curDisplayed) {
+					this.modulesDisplayed.removeIf(mod -> clazz.isAssignableFrom(mod.getClass()));
+					this.invokeSafe(clientModule, m -> ((AbstractClientModule) m).onHide());
+				}
+				this.modulesDisplayedClientModulesView = List.copyOf(this.modulesDisplayed);
+				
+				break;
+			}
+		}
+	}
+	
+	@Override
+	public boolean isDisplayed(final String className) {
+		try {
+			final var clazz = Class.forName(className);
+			return this.isDisplayed(clazz.asSubclass(AbstractClientModule.class));
+		}
+		catch (final ClassNotFoundException e) {
+			LOGGER.error("Class not found: " + className, e);
+			return false;
+		}
+	}
+	
+	@Override
+	public boolean isDisplayed(final Class<? extends AbstractClientModule> clazz) {
+		return this.modulesDisplayed.stream().anyMatch(m -> clazz.isAssignableFrom(m.getClass()));
+	}
+	
+	@Override
+	public void hideAll() {
+		this.lastVisibleStates.clear();
+		
+		for (final var module : List.copyOf(this.modulesDisplayed)) {
+			if ((module instanceof final AbstractClientModule clientModule) && !clientModule.isAlwaysDisplay()) {
+				this.changeDisplayState(clientModule.getClass(), false);
+			}
+		}
+	}
+	
+	@Override
+	@SafeVarargs
+	public final void hideExcept(final String... classNames) {
+		final List<AbstractClientModule> state = new ArrayList<>();
+		final var keep = new java.util.HashSet<>(java.util.Arrays.asList(classNames));
+		
+		for (final var module : List.copyOf(this.modulesDisplayed)) {
+			if (module instanceof final AbstractClientModule clientModule &&
+					!clientModule.isAlwaysDisplay() &&
+					!keep.contains(clientModule.getClass().getName())) {
+				this.changeDisplayState(clientModule.getClass(), false);
+				state.add(clientModule);
+			}
+		}
+		
+		if (!state.isEmpty()) {
+			this.lastVisibleStates.push(state);
+		}
+	}
+	
+	@Override
+	public void restoreVisibility() {
+		if (this.lastVisibleStates.isEmpty()) {
+			return;
+		}
+		
+		for (final AbstractClientModule module : this.lastVisibleStates.pop()) {
+			this.changeDisplayState(module.getClass(), true);
+		}
+	}
+	
+	@Override
+	public boolean isModal() {
+		return !this.lastVisibleStates.isEmpty();
+	}
+	
+	private void invokeSafe(final AbstractModule module, final Consumer<AbstractModule> consumer) {
+		try {
+			consumer.accept(module);
+		}
+		catch (final Exception exc) {
+			LOGGER.error("Error in module " + module.getClass().getName(), exc);
+		}
+	}
+	
+	private void sortModules(final List<AbstractModule> modules) {
+		modules.sort((o1, o2) -> {
+			if (o1 instanceof final AbstractClientModule a1 && o2 instanceof final AbstractClientModule a2) {
+				return Integer.compare(a2.getPriority(), a1.getPriority());
+			}
+			return Boolean.compare(o1 instanceof AbstractClientModule, o2 instanceof AbstractClientModule);
+		});
+	}
+	
+}
diff --git a/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports b/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
index a7aea4b..24817c5 100644
--- a/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
+++ b/src/main/resources/META-INF/spring/org.springframework.boot.autoconfigure.AutoConfiguration.imports
@@ -3,3 +3,4 @@ de.extio.game_engine.keyboard.KeycodeAutoConfiguration
 de.extio.game_engine.renderer.RendererAutoConfiguration
 de.extio.game_engine.renderer.g2d.G2DAutoConfiguration
 de.extio.game_engine.storage.StorageServiceAutoConfiguration
+de.extio.game_engine.module.ModuleManagerAutoConfiguration
diff --git a/src/test/java/de/extio/game_engine/module/ModuleManagerTest.java b/src/test/java/de/extio/game_engine/module/ModuleManagerTest.java
new file mode 100644
index 0000000..a853b12
--- /dev/null
+++ b/src/test/java/de/extio/game_engine/module/ModuleManagerTest.java
@@ -0,0 +1,504 @@
+package de.extio.game_engine.module;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+public class ModuleManagerTest {
+	
+	private ModuleManagerImpl moduleManager;
+	
+	private TestModule testModule;
+	
+	private TestClientModule testClientModule;
+	
+	@BeforeEach
+	public void setUp() throws Exception {
+		this.testModule = new TestModule();
+		this.testClientModule = new TestClientModule();
+		
+		final List<AbstractModule> initialModules = new ArrayList<>();
+		initialModules.add(this.testModule);
+		initialModules.add(this.testClientModule);
+		
+		this.moduleManager = new ModuleManagerImpl(initialModules);
+		this.moduleManager.afterPropertiesSet();
+	}
+	
+	@Test
+	public void testAfterPropertiesSet() {
+		assertEquals(2, this.moduleManager.getModulesAll().size());
+		assertTrue(this.testModule.onLoadCalled);
+		assertTrue(this.testClientModule.onLoadCalled);
+	}
+	
+	@Test
+	public void testAfterPropertiesSet_EmptyModules() throws Exception {
+		final ModuleManagerImpl emptyManager = new ModuleManagerImpl(List.of());
+		emptyManager.afterPropertiesSet();
+		
+		assertTrue(emptyManager.getModulesAll().isEmpty());
+	}
+	
+	@Test
+	public void testAfterPropertiesSet_NullModules() throws Exception {
+		final ModuleManagerImpl nullManager = new ModuleManagerImpl(null);
+		nullManager.afterPropertiesSet();
+		
+		assertTrue(nullManager.getModulesAll().isEmpty());
+	}
+	
+	@Test
+	public void testGetModulesAll() {
+		final List<AbstractModule> modules = this.moduleManager.getModulesAll();
+		
+		assertEquals(2, modules.size());
+		assertTrue(modules.contains(this.testModule));
+		assertTrue(modules.contains(this.testClientModule));
+	}
+	
+	@Test
+	public void testGetModulesActive_InitiallyEmpty() {
+		assertTrue(this.moduleManager.getModulesActive().isEmpty());
+	}
+	
+	@Test
+	public void testLoadModule() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		
+		assertEquals(3, this.moduleManager.getModulesAll().size());
+		assertTrue(this.moduleManager.getModulesAll().stream().anyMatch(m -> m instanceof AlwaysDisplayModule));
+	}
+	
+	@Test
+	public void testLoadModule_AlreadyLoaded() {
+		final int initialSize = this.moduleManager.getModulesAll().size();
+		
+		this.moduleManager.loadModule(TestModule.class);
+		
+		assertEquals(initialSize, this.moduleManager.getModulesAll().size());
+	}
+	
+	@Test
+	public void testUnloadModule() {
+		this.moduleManager.unloadModule(TestModule.class);
+		
+		assertEquals(1, this.moduleManager.getModulesAll().size());
+		assertFalse(this.moduleManager.getModulesAll().contains(this.testModule));
+		assertTrue(this.testModule.onUnloadCalled);
+	}
+	
+	@Test
+	public void testUnloadModule_NotLoaded() {
+		final int initialSize = this.moduleManager.getModulesAll().size();
+		
+		this.moduleManager.unloadModule(AlwaysDisplayModule.class);
+		
+		assertEquals(initialSize, this.moduleManager.getModulesAll().size());
+	}
+	
+	@Test
+	public void testUnloadModule_DeactivatesFirst() {
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		assertTrue(this.moduleManager.getModulesActive().contains(this.testModule));
+		
+		this.moduleManager.unloadModule(TestModule.class);
+		
+		assertFalse(this.moduleManager.getModulesActive().contains(this.testModule));
+		assertTrue(this.testModule.onDeactivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_Activate() {
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		
+		assertTrue(this.moduleManager.getModulesActive().contains(this.testModule));
+		assertTrue(this.testModule.onActivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_Deactivate() {
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		this.testModule.onActivateCalled = false;
+		
+		this.moduleManager.changeActiveState(TestModule.class, false);
+		
+		assertFalse(this.moduleManager.getModulesActive().contains(this.testModule));
+		assertTrue(this.testModule.onDeactivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_AlreadyActive() {
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		this.testModule.onActivateCalled = false;
+		
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		
+		assertFalse(this.testModule.onActivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_AlreadyInactive() {
+		this.moduleManager.changeActiveState(TestModule.class, false);
+		
+		assertFalse(this.testModule.onDeactivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_ByClassName() {
+		this.moduleManager.changeActiveState(TestModule.class.getName(), true);
+		
+		assertTrue(this.moduleManager.getModulesActive().contains(this.testModule));
+		assertTrue(this.testModule.onActivateCalled);
+	}
+	
+	@Test
+	public void testChangeActiveState_AlwaysDisplayModule() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		
+		this.moduleManager.changeActiveState(AlwaysDisplayModule.class, true);
+		
+		assertTrue(this.moduleManager.isDisplayed(AlwaysDisplayModule.class));
+	}
+	
+	@Test
+	public void testDeactivateAll() {
+		this.moduleManager.changeActiveState(TestModule.class, true);
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		
+		this.moduleManager.deactivateAll();
+		
+		assertTrue(this.moduleManager.getModulesActive().isEmpty());
+		assertTrue(this.testModule.onDeactivateCalled);
+		assertTrue(this.testClientModule.onDeactivateCalled);
+	}
+	
+	@Test
+	public void testChangeDisplayState_Show() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.testClientModule.onShowCalled = false;
+		
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		
+		assertTrue(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onShowCalled);
+	}
+	
+	@Test
+	public void testChangeDisplayState_Hide() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.testClientModule.onHideCalled = false;
+		
+		this.moduleManager.changeDisplayState(TestClientModule.class, false);
+		
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onHideCalled);
+	}
+	
+	@Test
+	public void testChangeDisplayState_AlreadyShown() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.testClientModule.onShowCalled = false;
+		
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		
+		assertFalse(this.testClientModule.onShowCalled, "onShow should not be called when already shown");
+	}
+	
+	@Test
+	public void testChangeDisplayState_AlreadyHidden() {
+		this.testClientModule.onHideCalled = false;
+		
+		this.moduleManager.changeDisplayState(TestClientModule.class, false);
+		
+		assertFalse(this.testClientModule.onHideCalled, "onHide should not be called when already hidden");
+	}
+	
+	@Test
+	public void testChangeDisplayState_ByClassName() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.testClientModule.onShowCalled = false;
+		
+		this.moduleManager.changeDisplayState(TestClientModule.class.getName(), true);
+		
+		assertTrue(this.moduleManager.isDisplayed(TestClientModule.class));
+	}
+	
+	@Test
+	public void testChangeDisplayState_AlwaysDisplayModule() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		this.moduleManager.changeActiveState(AlwaysDisplayModule.class, true);
+		
+		this.moduleManager.changeDisplayState(AlwaysDisplayModule.class, false);
+		
+		assertTrue(this.moduleManager.isDisplayed(AlwaysDisplayModule.class));
+	}
+	
+	@Test
+	public void testIsDisplayed_ByClassName() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		
+		assertTrue(this.moduleManager.isDisplayed(TestClientModule.class.getName()));
+	}
+	
+	@Test
+	public void testHideAll() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.testClientModule.onHideCalled = false;
+		
+		this.moduleManager.hideAll();
+		
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onHideCalled);
+	}
+	
+	@Test
+	public void testHideAll_DoesNotHideAlwaysDisplay() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		this.moduleManager.changeActiveState(AlwaysDisplayModule.class, true);
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		
+		this.moduleManager.hideAll();
+		
+		assertTrue(this.moduleManager.isDisplayed(AlwaysDisplayModule.class));
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+	}
+	
+	@Test
+	public void testHideExcept() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.moduleManager.changeActiveState(AlwaysDisplayModule.class, true);
+		this.testClientModule.onHideCalled = false;
+		
+		this.moduleManager.hideExcept(AlwaysDisplayModule.class.getName());
+		
+		assertTrue(this.moduleManager.isDisplayed(AlwaysDisplayModule.class));
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onHideCalled);
+	}
+	
+	@Test
+	public void testHideExcept_MultipleExceptions() {
+		this.moduleManager.loadModule(AlwaysDisplayModule.class);
+		this.moduleManager.loadModule(HighPriorityModule.class);
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.moduleManager.changeActiveState(AlwaysDisplayModule.class, true);
+		this.moduleManager.changeActiveState(HighPriorityModule.class, true);
+		this.moduleManager.changeDisplayState(HighPriorityModule.class, true);
+		
+		this.moduleManager.hideExcept(
+				AlwaysDisplayModule.class.getName(),
+				HighPriorityModule.class.getName()
+		);
+		
+		assertTrue(this.moduleManager.isDisplayed(AlwaysDisplayModule.class));
+		assertTrue(this.moduleManager.isDisplayed(HighPriorityModule.class));
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+	}
+	
+	@Test
+	public void testRestoreVisibility() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		
+		this.moduleManager.hideExcept();
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+		this.testClientModule.onShowCalled = false;
+		
+		this.moduleManager.restoreVisibility();
+		
+		assertTrue(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onShowCalled);
+	}
+	
+	@Test
+	public void testRestoreVisibility_NoState() {
+		this.moduleManager.restoreVisibility();
+		
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+	}
+	
+	@Test
+	public void testIsModal() {
+		assertFalse(this.moduleManager.isModal());
+		
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.moduleManager.hideExcept();
+		
+		assertTrue(this.moduleManager.isModal());
+		
+		this.moduleManager.restoreVisibility();
+		
+		assertFalse(this.moduleManager.isModal());
+	}
+	
+	@Test
+	public void testModuleSorting_Priority() {
+		this.moduleManager.loadModule(HighPriorityModule.class);
+		
+		final List<AbstractModule> modules = this.moduleManager.getModulesAll();
+		
+		assertEquals(3, modules.size());
+		
+		int highPriorityIndex = -1;
+		int normalPriorityIndex = -1;
+		int nonClientIndex = -1;
+		
+		for (int i = 0; i < modules.size(); i++) {
+			if (modules.get(i) instanceof HighPriorityModule) {
+				highPriorityIndex = i;
+			}
+			else if (modules.get(i) instanceof TestClientModule) {
+				normalPriorityIndex = i;
+			}
+			else if (modules.get(i) instanceof TestModule) {
+				nonClientIndex = i;
+			}
+		}
+		
+		assertTrue(highPriorityIndex >= 0);
+		assertTrue(normalPriorityIndex >= 0);
+		assertTrue(nonClientIndex >= 0);
+		assertTrue(highPriorityIndex < normalPriorityIndex, 
+				"High priority (" + highPriorityIndex + ") should come before normal (" + normalPriorityIndex + ")");
+		assertTrue(nonClientIndex < normalPriorityIndex,
+				"Non-client (" + nonClientIndex + ") should come before client (" + normalPriorityIndex + ")");
+		assertTrue(nonClientIndex < highPriorityIndex,
+				"Non-client (" + nonClientIndex + ") should come before high priority client (" + highPriorityIndex + ")");
+	}
+	
+	@Test
+	public void testDeactivate_HidesDisplayedClientModule() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.testClientModule.onHideCalled = false;
+		
+		this.moduleManager.changeActiveState(TestClientModule.class, false);
+		
+		assertFalse(this.moduleManager.isDisplayed(TestClientModule.class));
+		assertTrue(this.testClientModule.onHideCalled);
+	}
+	
+	@Test
+	public void testDeactivateAll_ClearsVisibilityStack() {
+		this.moduleManager.changeActiveState(TestClientModule.class, true);
+		this.moduleManager.changeDisplayState(TestClientModule.class, true);
+		this.moduleManager.hideExcept();
+		
+		assertTrue(this.moduleManager.isModal());
+		
+		this.moduleManager.deactivateAll();
+		
+		assertFalse(this.moduleManager.isModal());
+	}
+	
+	static class TestModule extends AbstractModule {
+		
+		boolean onLoadCalled = false;
+		
+		boolean onUnloadCalled = false;
+		
+		boolean onActivateCalled = false;
+		
+		boolean onDeactivateCalled = false;
+		
+		@Override
+		public void onLoad() {
+			this.onLoadCalled = true;
+		}
+		
+		@Override
+		public void onUnload() {
+			this.onUnloadCalled = true;
+		}
+		
+		@Override
+		public void onActivate() {
+			this.onActivateCalled = true;
+		}
+		
+		@Override
+		public void onDeactivate() {
+			this.onDeactivateCalled = true;
+		}
+		
+	}
+	
+	static class TestClientModule extends AbstractClientModule {
+		
+		boolean onLoadCalled = false;
+		
+		boolean onUnloadCalled = false;
+		
+		boolean onActivateCalled = false;
+		
+		boolean onDeactivateCalled = false;
+		
+		boolean onShowCalled = false;
+		
+		boolean onHideCalled = false;
+		
+		@Override
+		public void onLoad() {
+			this.onLoadCalled = true;
+		}
+		
+		@Override
+		public void onUnload() {
+			this.onUnloadCalled = true;
+		}
+		
+		@Override
+		public void onActivate() {
+			this.onActivateCalled = true;
+		}
+		
+		@Override
+		public void onDeactivate() {
+			this.onDeactivateCalled = true;
+		}
+		
+		@Override
+		public void onShow() {
+			this.onShowCalled = true;
+		}
+		
+		@Override
+		public void onHide() {
+			this.onHideCalled = true;
+		}
+		
+	}
+	
+	static class AlwaysDisplayModule extends AbstractClientModule {
+		
+		@Override
+		public boolean isAlwaysDisplay() {
+			return true;
+		}
+		
+	}
+	
+	static class HighPriorityModule extends AbstractClientModule {
+		
+		@Override
+		public int getPriority() {
+			return MODULE_PRIORITY_HIGH;
+		}
+		
+	}
+	
+}