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, 261 insertions, 0 deletions

diff --git a/src/game/data.cpp b/src/game/data.cpp
new file mode 100644
index 0000000..54f7fdb
--- /dev/null
+++ b/src/game/data.cpp
@@ -0,0 +1,261 @@
+#include "game/data.hpp"
+#include "engine/script.hpp"
+
+#include <filesystem>
+#include <algorithm>
+#include <cstdio>
+
+// sol2's string-literal table keys trip a GCC -Warray-bounds false positive
+// under inlining/optimisation. The access is correct; silence the noise here.
+#if defined(__GNUC__) && !defined(__clang__)
+#pragma GCC diagnostic ignored "-Warray-bounds"
+#endif
+
+namespace fs = std::filesystem;
+
+namespace {
+constexpr float DEG2RAD = 3.14159265358979323846f / 180.0f;
+
+MaterialDef read_material(const sol::table& m) {
+    MaterialDef d{};
+    d.name            = m.get_or("name", std::string("unnamed"));
+    d.stiffness       = m.get_or("stiffness", 600.0f);
+    d.damping         = m.get_or("damping", 12.0f);
+    d.mass            = m.get_or("mass", 0.25f);
+    d.max_compression = m.get_or("max_compression", 0.90f);
+    d.max_expansion   = m.get_or("max_expansion", 1.10f);
+    d.angle_threshold = m.get_or("angle_threshold", 30.0f) * DEG2RAD;  // data is degrees
+    d.min_length      = m.get_or("min_length", 0.4f);
+    d.max_length      = m.get_or("max_length", 3.0f);
+    d.max_link_length = m.get_or("max_link_length", 6.0f);
+    d.hit_points      = m.get_or("hit_points", 150.0f);
+    d.flammable       = m.get_or("flammable", true);
+    d.burn_rate       = m.get_or("burn_rate", 15.0f);
+    d.spread_time     = m.get_or("spread_time", 2.0f);
+    d.blocks_projectiles = m.get_or("blocks_projectiles", true);
+    d.blocks_beam        = m.get_or("blocks_beam", true);
+    d.tension_only    = m.get_or("tension_only", false);
+    d.half_width      = m.get_or("half_width", 0.15f);
+    d.texture         = m.get_or("texture", std::string(""));
+
+    sol::optional<sol::table> col = m["color"];
+    d.r = col ? col->get_or(1, 0.8f) : 0.8f;
+    d.g = col ? col->get_or(2, 0.5f) : 0.5f;
+    d.b = col ? col->get_or(3, 0.2f) : 0.2f;
+    d.a = col ? col->get_or(4, 1.0f) : 1.0f;
+    return d;
+}
+} // namespace
+
+std::vector<MaterialDef> load_materials(ScriptEngine& script,
+                                        const std::string& data_dir) {
+    std::vector<MaterialDef> out;
+
+    // 1. Base data.
+    if (!script.run_file(data_dir + "/materials.lua")) return out;
+
+    // 2. Mods, ordered by (priority asc, path). Each mod.lua sets Priority;
+    //    each materials.lua mutates the shared global Materials table.
+    std::error_code ec;
+    std::string mods_dir = data_dir + "/mods";
+    std::vector<std::pair<int, std::string>> mods;
+    if (fs::is_directory(mods_dir, ec)) {
+        for (const auto& e : fs::directory_iterator(mods_dir, ec)) {
+            if (!e.is_directory()) continue;
+            std::string mp = e.path().string();
+            if (!fs::exists(mp + "/materials.lua")) continue;
+            int priority = 5;
+            if (fs::exists(mp + "/mod.lua") && script.run_file(mp + "/mod.lua")) {
+                sol::optional<int> p = script.lua()["Priority"];
+                if (p) priority = *p;
+            }
+            mods.emplace_back(priority, mp);
+        }
+        std::sort(mods.begin(), mods.end());
+        for (const auto& [prio, mp] : mods) {
+            printf("Mod: applying %s (priority %d)\n", mp.c_str(), prio);
+            script.run_file(mp + "/materials.lua");
+        }
+    }
+
+    // 3. Read the final Materials array (1-based Lua array part, in order).
+    sol::optional<sol::table> mats = script.lua()["Materials"];
+    if (!mats) {
+        fprintf(stderr, "load_materials: no global 'Materials' table\n");
+        return out;
+    }
+    for (std::size_t i = 1; ; i++) {
+        sol::object o = (*mats)[i];
+        if (o.get_type() != sol::type::table) break;
+        out.push_back(read_material(o.as<sol::table>()));
+    }
+    printf("Loaded %zu materials from Lua\n", out.size());
+    return out;
+}
+
+namespace {
+// Run <data_dir>/<file> then every mod's <file> (priority, name order).
+void run_layered(ScriptEngine& script, const std::string& data_dir,
+                 const std::string& file) {
+    if (!script.run_file(data_dir + "/" + file)) return;
+    std::error_code ec;
+    std::string mods_dir = data_dir + "/mods";
+    std::vector<std::pair<int, std::string>> mods;
+    if (fs::is_directory(mods_dir, ec)) {
+        for (const auto& e : fs::directory_iterator(mods_dir, ec)) {
+            if (!e.is_directory()) continue;
+            std::string mp = e.path().string();
+            if (!fs::exists(mp + "/" + file)) continue;
+            int priority = 5;
+            if (fs::exists(mp + "/mod.lua") && script.run_file(mp + "/mod.lua")) {
+                sol::optional<int> p = script.lua()["Priority"];
+                if (p) priority = *p;
+            }
+            mods.emplace_back(priority, mp);
+        }
+        std::sort(mods.begin(), mods.end());
+        for (const auto& [prio, mp] : mods)
+            script.run_file(mp + "/" + file);
+    }
+}
+
+WeaponDef read_weapon(const sol::table& w) {
+    WeaponDef d{};
+    d.name               = w.get_or("name", std::string("unnamed"));
+    d.muzzle_speed       = w.get_or("muzzle_speed", 35.0f);
+    d.reload             = w.get_or("reload", 2.0f);
+    d.splash_damage      = w.get_or("splash_damage", 200.0f);
+    d.splash_radius      = w.get_or("splash_radius", 3.0f);
+    d.knockback          = w.get_or("knockback", 60.0f);
+    d.projectile_radius  = w.get_or("projectile_radius", 0.15f);
+    d.fire_chance        = w.get_or("fire_chance", 0.0f);
+    d.min_fire_angle     = w.get_or("min_fire_angle", -20.0f) * DEG2RAD;
+    d.max_fire_angle     = w.get_or("max_fire_angle",  30.0f) * DEG2RAD;
+    d.is_beam            = w.get_or("is_beam", false);
+    d.beam_range         = w.get_or("beam_range", 60.0f);
+    d.beam_dps           = w.get_or("beam_dps", 120.0f);
+    d.beam_duration      = w.get_or("beam_duration", 1.5f);
+    d.energy_cost        = w.get_or("energy_cost", 0.0f);
+    d.texture            = w.get_or("texture", std::string(""));
+    d.projectile_texture = w.get_or("projectile_texture", std::string(""));
+    return d;
+}
+} // namespace
+
+std::vector<WeaponDef> load_weapons(ScriptEngine& script, const std::string& data_dir) {
+    std::vector<WeaponDef> out;
+    run_layered(script, data_dir, "weapons.lua");
+    sol::optional<sol::table> ws = script.lua()["Weapons"];
+    if (!ws) { fprintf(stderr, "load_weapons: no global 'Weapons' table\n"); return out; }
+    for (std::size_t i = 1; ; i++) {
+        sol::object o = (*ws)[i];
+        if (o.get_type() != sol::type::table) break;
+        out.push_back(read_weapon(o.as<sol::table>()));
+    }
+    printf("Loaded %zu weapons from Lua\n", out.size());
+    return out;
+}
+
+void load_structures(ScriptEngine& script, const std::string& data_dir,
+                     BuildGraph& graph) {
+    run_layered(script, data_dir, "structures.lua");
+    sol::optional<sol::table> structs = script.lua()["Structures"];
+    if (!structs) return;
+
+    auto mat_index = [&](const std::string& nm) -> int {
+        for (int i = 0; i < (int)graph.materials.size(); i++)
+            if (graph.materials[i].name == nm) return i;
+        return 0;
+    };
+    auto node_at = [&](float x, float y) -> int {
+        int n = graph.find_nearest_node(x, y, BuildGraph::SNAP_RADIUS);
+        return (n >= 0) ? n : graph.add_node(x, y, graph.is_on_ground(y));
+    };
+
+    int built = 0;
+    for (std::size_t si = 1; ; si++) {
+        sol::object so = (*structs)[si];
+        if (so.get_type() != sol::type::table) break;
+        sol::table S = so.as<sol::table>();
+        sol::optional<sol::table> beams = S["beams"];
+        if (!beams) continue;
+        for (std::size_t bi = 1; ; bi++) {
+            sol::object bo = (*beams)[bi];
+            if (bo.get_type() != sol::type::table) break;
+            sol::table b = bo.as<sol::table>();
+            float x1 = b.get_or(1, 0.0f), y1 = b.get_or(2, 0.0f);
+            float x2 = b.get_or(3, 0.0f), y2 = b.get_or(4, 0.0f);
+            std::string mat = b.get_or(5, std::string("wood"));
+            if (graph.add_edge(node_at(x1, y1), node_at(x2, y2), mat_index(mat)) >= 0)
+                built++;
+        }
+    }
+    for (auto& e : graph.edges) e.settle = 0.0f;   // prebuilt = already cured
+    printf("Loaded %d prebuilt struts from Structures\n", built);
+}
+
+namespace {
+DeviceDef read_device(const sol::table& d) {
+    DeviceDef v{};
+    v.name            = d.get_or("name", std::string("device"));
+    v.hp              = d.get_or("hp", 100.0f);
+    v.energy_rate     = d.get_or("energy_rate", 0.0f);
+    v.metal_rate      = d.get_or("metal_rate", 0.0f);
+    v.energy_storage  = d.get_or("energy_storage", 0.0f);
+    v.metal_storage   = d.get_or("metal_storage", 0.0f);
+    v.needs_deposit   = d.get_or("needs_deposit", false);
+    v.wind            = d.get_or("wind", false);
+    v.wind_max_rate   = d.get_or("wind_max_rate", 15.0f);
+    v.wind_max_height = d.get_or("wind_max_height", 20.0f);
+    v.is_core         = d.get_or("is_core", false);
+    v.half_w          = d.get_or("half_w", 0.6f);
+    v.half_h          = d.get_or("half_h", 0.6f);
+    v.cost_metal      = d.get_or("cost_metal", 0.0f);
+    v.cost_energy     = d.get_or("cost_energy", 0.0f);
+    v.texture         = d.get_or("texture", std::string(""));
+    sol::optional<sol::table> col = d["color"];
+    v.r = col ? col->get_or(1, 0.8f) : 0.8f;
+    v.g = col ? col->get_or(2, 0.8f) : 0.8f;
+    v.b = col ? col->get_or(3, 0.8f) : 0.8f;
+    return v;
+}
+} // namespace
+
+std::vector<DeviceDef> load_devices(ScriptEngine& script, const std::string& data_dir) {
+    std::vector<DeviceDef> out;
+    run_layered(script, data_dir, "devices.lua");
+    sol::optional<sol::table> ds = script.lua()["DeviceDefs"];
+    if (!ds) { fprintf(stderr, "load_devices: no 'DeviceDefs' table\n"); return out; }
+    for (std::size_t i = 1; ; i++) {
+        sol::object o = (*ds)[i];
+        if (o.get_type() != sol::type::table) break;
+        out.push_back(read_device(o.as<sol::table>()));
+    }
+    printf("Loaded %zu devices from Lua\n", out.size());
+    return out;
+}
+
+MapData load_map(ScriptEngine& script, const std::string& data_dir) {
+    MapData m;
+    run_layered(script, data_dir, "map.lua");
+    if (sol::optional<sol::table> dep = script.lua()["Deposits"]) {
+        for (std::size_t i = 1; ; i++) {
+            sol::object o = (*dep)[i];
+            if (o.get_type() != sol::type::table) break;
+            sol::table p = o.as<sol::table>();
+            m.deposits.emplace_back(p.get_or(1, 0.0f), p.get_or(2, 0.0f));
+        }
+    }
+    if (sol::optional<sol::table> md = script.lua()["MapDevices"]) {
+        for (std::size_t i = 1; ; i++) {
+            sol::object o = (*md)[i];
+            if (o.get_type() != sol::type::table) break;
+            sol::table d = o.as<sol::table>();
+            m.devices.push_back({ d.get_or("type", std::string("reactor")),
+                                  d.get_or("x", 0.0f), d.get_or("y", 0.0f),
+                                  d.get_or("team", 0) });
+        }
+    }
+    printf("Loaded map: %zu deposits, %zu devices\n", m.deposits.size(), m.devices.size());
+    return m;
+}