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, 55 insertions, 0 deletions

diff --git a/src/engine/camera.cpp b/src/engine/camera.cpp
new file mode 100644
index 0000000..6ab2c57
--- /dev/null
+++ b/src/engine/camera.cpp
@@ -0,0 +1,55 @@
+#include "engine/camera.hpp"
+
+void Camera::set_viewport(int width, int height) {
+    vp_width_  = width;
+    vp_height_ = height;
+}
+
+void Camera::set_position(glm::vec2 pos) {
+    pos_ = pos;
+}
+
+void Camera::set_zoom(float zoom) {
+    if (zoom < min_zoom) zoom = min_zoom;
+    if (zoom > max_zoom) zoom = max_zoom;
+    zoom_ = zoom;
+}
+
+void Camera::pan(glm::vec2 delta) {
+    pos_ += delta;
+}
+
+void Camera::zoom_at(float delta, glm::vec2 world_cursor) {
+    float new_zoom = zoom_ * (1.0f + delta * zoom_speed);
+    if (new_zoom < min_zoom) new_zoom = min_zoom;
+    if (new_zoom > max_zoom) new_zoom = max_zoom;
+
+    // Adjust position so world_cursor stays under the same screen point
+    float ratio = zoom_ / new_zoom;
+    pos_ = world_cursor + (pos_ - world_cursor) * ratio;
+    zoom_ = new_zoom;
+}
+
+void Camera::compute_view_proj() {
+    float half_w = (vp_width_  / zoom_) * 0.5f;
+    float half_h = (vp_height_ / zoom_) * 0.5f;
+
+    proj_ = glm::ortho(-half_w, half_w, -half_h, half_h, -1.0f, 1.0f);
+    view_ = glm::translate(glm::mat4(1.0f), glm::vec3(-pos_.x, -pos_.y, 0.0f));
+
+    glm::mat4 vp = proj_ * view_;
+
+    // Copy to column-major float array for bgfx
+    const float* src = &vp[0][0];
+    float* dst = &vp_[0][0];
+    for (int i = 0; i < 16; i++) {
+        dst[i] = src[i];
+    }
+}
+
+glm::vec2 Camera::screen_to_world(glm::vec2 screen) const {
+    // Convert from screen (y-down) to world (y-up)
+    float world_x = pos_.x + (screen.x - vp_width_  * 0.5f) / zoom_;
+    float world_y = pos_.y - (screen.y - vp_height_ * 0.5f) / zoom_;
+    return glm::vec2(world_x, world_y);
+}