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, 59 insertions, 0 deletions

diff --git a/src/engine/camera.hpp b/src/engine/camera.hpp
new file mode 100644
index 0000000..ecaadc1
--- /dev/null
+++ b/src/engine/camera.hpp
@@ -0,0 +1,59 @@
+#pragma once
+
+#include <glm/glm.hpp>
+#include <glm/gtc/matrix_transform.hpp>
+
+// 2D orthographic camera. Works in world-space coordinates (Box2D space).
+// x+ = right, y+ = up.
+
+class Camera {
+public:
+    Camera() = default;
+
+    // Set the viewport size in pixels (window size).
+    void set_viewport(int width, int height);
+
+    // World-space position the camera is looking at.
+    void set_position(glm::vec2 pos);
+    glm::vec2 position() const { return pos_; }
+
+    // Zoom: higher = more zoomed in. Clamped to [min_zoom, max_zoom].
+    void set_zoom(float zoom);
+    float zoom() const { return zoom_; }
+
+    // Pan by delta in world units (not pixels).
+    void pan(glm::vec2 delta);
+
+    // Zoom by delta at the given screen position (world-space under cursor).
+    void zoom_at(float delta, glm::vec2 world_cursor);
+
+    // Build view-projection matrix. Call once per frame.
+    void compute_view_proj();
+
+    const float* view_proj() const { return &vp_[0][0]; }
+    glm::mat4    view() const       { return view_; }
+    glm::mat4    proj() const       { return proj_; }
+
+    // Convert screen coordinates (pixels, y-down) to world coordinates.
+    glm::vec2 screen_to_world(glm::vec2 screen) const;
+
+    int viewport_width()  const { return vp_width_; }
+    int viewport_height() const { return vp_height_; }
+
+    // Config
+    float min_zoom   = 0.1f;
+    float max_zoom   = 200.0f;
+    float zoom_speed = 0.1f;
+    float pan_speed  = 500.0f;  // pixels per second
+
+private:
+    glm::vec2 pos_   = {0.0f, 5.0f};     // world center at start
+    float     zoom_  = 10.0f;            // pixels per world unit
+
+    int vp_width_  = 1280;
+    int vp_height_ = 720;
+
+    glm::mat4 view_ = glm::mat4(1.0f);
+    glm::mat4 proj_ = glm::mat4(1.0f);
+    float     vp_[4][4] = {};   // column-major for bgfx
+};