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, 62 insertions, 0 deletions

diff --git a/data/materials.lua b/data/materials.lua
new file mode 100644
index 0000000..a2f876c
--- /dev/null
+++ b/data/materials.lua
@@ -0,0 +1,62 @@
+-- Base building materials for the clone.
+--
+-- The engine reads the global `Materials` array (in order). Build modes 1/2/3
+-- map to entries 1/2/3. Mods under data/mods/ run AFTER this file and may use
+-- FindMaterial(name) to tweak these, or table.insert(Materials, ...) to add new
+-- ones. (angle_threshold is in DEGREES; the engine converts to radians.)
+
+Materials =
+{
+    {
+        name = "wood",
+        stiffness = 600, damping = 12, mass = 0.25,
+        max_compression = 0.90, max_expansion = 1.10,  -- snaps past +/-10% length
+        angle_threshold = 30, tension_only = false,    -- snaps if a loose strut rotates >30deg
+        min_length = 0.4, max_length = 3.0, max_link_length = 6.0,  -- single-strut size limits
+        hit_points = 150,
+        flammable = true, burn_rate = 15, spread_time = 2.0,   -- wood: slow burn/spread
+        blocks_projectiles = true, blocks_beam = true,         -- solid: stops shells & beams
+        half_width = 0.15,
+        color = { 1.0, 1.0, 1.0, 1.0 },                 -- white = show texture untinted
+        texture = "data/textures/wood.png",
+    },
+    {
+        name = "bgbrace",                               -- background bracing
+        stiffness = 600, damping = 12, mass = 0.25,
+        max_compression = 0.92, max_expansion = 1.08,
+        angle_threshold = 30, tension_only = false,
+        min_length = 0.4, max_length = 3.0, max_link_length = 6.0,
+        hit_points = 100,
+        flammable = true, burn_rate = 22, spread_time = 0.7,   -- burns ~3x faster than wood
+        blocks_projectiles = false, blocks_beam = false,       -- shells AND beams pass through (beam still burns it)
+        half_width = 0.15,
+        color = { 1.0, 1.0, 1.0, 0.45 },                -- translucent
+        texture = "data/textures/bgbrace.png",
+    },
+    {
+        name = "rope",
+        stiffness = 150, damping = 8, mass = 0.05,
+        max_compression = 0.0, max_expansion = 1.50,    -- slack in compression, snaps at +50%
+        angle_threshold = 360, tension_only = true,     -- never snaps on angle
+        min_length = 0.8, max_length = 1.5, max_link_length = 20.0,  -- subdivides into many segments -> drapes
+        hit_points = 50,
+        flammable = true, burn_rate = 25, spread_time = 1.0,   -- burns through fast
+        blocks_projectiles = false, blocks_beam = false,       -- shells AND beams pass through
+        half_width = 0.04,
+        color = { 0.15, 0.12, 0.10, 1.0 },
+    },
+}
+
+-- Helpers mods can use (mirrors the Forts modding API shape).
+function IndexOfMaterial(name)
+    for i, m in ipairs(Materials) do
+        if m.name == name then return i end
+    end
+    return nil
+end
+
+function FindMaterial(name)
+    local i = IndexOfMaterial(name)
+    if i then return Materials[i] end
+    return nil
+end