diff --git a/Sources/SwiftFrontend/Application.swift b/Sources/SwiftFrontend/Application.swift
index f7a24ec..d47be0c 100644
--- a/Sources/SwiftFrontend/Application.swift
+++ b/Sources/SwiftFrontend/Application.swift
@@ -8,51 +8,84 @@
 import Foundation
 import SDL3
 
-struct Application {
-  func run() -> Int32 {
+class Application {
+  private var window: OpaquePointer? = nil
+  private var renderer: OpaquePointer? = nil
+
+  private func initialize() -> ApplicationExecutionState {
     guard SDL_Init(SDL_INIT_VIDEO) >= 0 else {
-      print("SDL init failed.")
-      return 1
+      print("SDL_Init() error: \(String(cString: SDL_GetError()))")
+      return .exitFailure
     }
-    
-    defer {
-      SDL_Quit()
+
+    window = SDL_CreateWindow("Hello World", 512, 512, 0)
+    guard window != nil else {
+      print("SDL_CreateWindow() error: \(String(cString: SDL_GetError()))")
+      return .exitFailure
     }
-    
-    guard let window = SDL_CreateWindow("Hello World", 512, 512, 0) else {
-      return 1
+
+    renderer = SDL_CreateRenderer(window, nil)
+    guard renderer != nil else {
+      print("SDL_CreateRenderer() error: \(String(cString: SDL_GetError()))")
+      return .exitFailure
     }
-    
-    defer {
-      SDL_DestroyWindow(window)
+
+    return .running
+  }
+
+  private func deinitialize() {
+    SDL_DestroyRenderer(renderer)
+    SDL_DestroyWindow(window)
+    SDL_Quit()
+  }
+
+  private func handleEvent(_ event: SDL_Event) -> ApplicationExecutionState {
+    switch SDL_EventType(event.type) {
+    case SDL_EVENT_QUIT:
+      return .exitSuccess
+
+    case SDL_EVENT_KEY_DOWN:
+      switch event.key.key {
+      case SDLK_ESCAPE:
+        return .exitSuccess
+      default:
+        break
+      }
+      return .running
+
+    default:
+      return .running
     }
-    
-    let renderer = SDL_CreateRenderer(window, nil)
-    
-    defer {
-      SDL_DestroyRenderer(renderer)
-    }
-    
-    quit: while true {
+  }
+
+  private func paint() -> ApplicationExecutionState {
+    SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255)
+    SDL_RenderClear(renderer)
+    var rect = SDL_FRect(x: 0, y: 0, w: 100, h: 100)
+    SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255)
+    SDL_RenderFillRect(renderer, &rect)
+    SDL_RenderPresent(renderer)
+    return .running
+  }
+
+  func run() -> Int32 {
+    var res = initialize()
+    quit: while res == .running {
       var event = SDL_Event()
-      
       while SDL_PollEvent(&event) > 0 {
-        switch SDL_EventType(event.type) {
-        case SDL_EVENT_QUIT:
+        res = handleEvent(event)
+        if res != .running {
           break quit
-        default:
-          break
         }
       }
-
-      SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255)
-      SDL_RenderClear(renderer)
-      var rect = SDL_FRect(x: 0, y: 0, w: 100, h: 100)
-      SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255)
-      SDL_RenderFillRect(renderer, &rect)
-      SDL_RenderPresent(renderer)
+      res = paint()
     }
-    
-    return 0
+    return res == .exitSuccess ? 0 : 1
   }
 }
+
+fileprivate enum ApplicationExecutionState {
+  case exitFailure
+  case exitSuccess
+  case running
+}