Initial import: LibreForts (M0-M5 in progress)

Open-source Forts clone: custom C++20 engine + data-driven (Lua) 2D physics
artillery RTS.

- Building: node/strut graph on a stiff mass-spring solver (canon Forts model),
  triangulation rigidity, axial + 30-degree angle-stress breaking, cascading
  collapse, fire (DoT + spread), ground destroys debris.
- Weapons (M4): cannon (ballistic) + laser (beam/ignite) with select-and-aim-in-
  arc UX; splash / beam damage; bg-brace passthrough.
- Devices + economy (M5): reactors + win/loss + restart, mines/turbines/battery,
  metal deposits, storage caps, per-shot energy cost.
- Data-driven via Lua/sol2 with a layered mod loader; enemy-fort scenario mod.
- Renderer: SDL3 + textures + ImGui dev UI. stb_image + ImGui vendored.
- Assets: CC0 placeholders only; real game art loaded at runtime from the user's
  own install via forts: paths (bring-your-own; nothing copyrighted committed).

See README.md / CLAUDE.md and research/ + requirements/ for detail.

1 files changed, 29 insertions, 0 deletions

diff --git a/src/engine/app.hpp b/src/engine/app.hpp
new file mode 100644
index 0000000..a57fdbe
--- /dev/null
+++ b/src/engine/app.hpp
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <SDL3/SDL.h>
+
+struct AppConfig {
+    const char* title = "Forts Clone";
+    int window_width = 1280;
+    int window_height = 720;
+};
+
+class App {
+public:
+    explicit App(const AppConfig& cfg = {});
+    ~App();
+
+    App(const App&) = delete;
+    App& operator=(const App&) = delete;
+
+    void run();
+
+private:
+    void update(float dt);
+    void render();
+
+    SDL_Window*  window_   = nullptr;
+    AppConfig     config_;
+    bool          running_  = true;
+    uint64_t      last_tick_ = 0;
+};