6 files changed, 52 insertions, 11 deletions
diff --git a/src/chunk.hpp b/src/chunk.hpp
index 031ba88e..8453bf83 100644
--- a/src/chunk.hpp
+++ b/src/chunk.hpp
@@ -118,7 +118,7 @@ private:
     std::array<std::shared_ptr<tile_atlas>, TILE_COUNT> _ground_atlases;
     std::array<uint8_t, TILE_COUNT> ground_indexes = {};
     std::array<variant_t, TILE_COUNT> _ground_variants = {};
-    std::array<std::shared_ptr<tile_atlas>, TILE_COUNT*2> _wall_atlases;
+    std::array<std::shared_ptr<tile_atlas>, TILE_COUNT*2> _wall_atlases; // todo make into vector
     std::array<uint16_t, TILE_COUNT*2> wall_indexes = {};
     std::array<variant_t, TILE_COUNT*2> _wall_variants = {};
     std::vector<std::shared_ptr<entity>> _entities;
diff --git a/src/entity.cpp b/src/entity.cpp
index 13f19620..8aa3752f 100644
--- a/src/entity.cpp
+++ b/src/entity.cpp
@@ -170,10 +170,7 @@ bool entity::can_move_to(Vector2i delta, global_coords coord2, Vector2b offset,
     auto ch = chunk_coords_{coord_.chunk(), coord_.z()};
     if (!do_search<false>(&c_, ch, id, min, max))
         return false;
-    constexpr Vector2b offsets[] = {
-        {-1, -1}, {-1,  0}, { 0, -1}, { 1,  1}, { 1,  0}, { 0,  1}, { 1, -1}, {-1,  1},
-    };
-    for (const auto& off : offsets)
+    for (const auto& off : world::neighbor_offsets)
         if (!do_search(&c_, ch, id, min, max, off))
             return false;
     return true;
diff --git a/src/global-coords.cpp b/src/global-coords.cpp
index de7c9ee2..6ffc06e1 100644
--- a/src/global-coords.cpp
+++ b/src/global-coords.cpp
@@ -18,4 +18,10 @@ static_assert(global_coords{(1u + (1<<15)) << 4 | 3, (2u + (1<<15)) << 4 | 4, nu
 static_assert(global_coords{-123, 456, 1}.z() == 1);
 static_assert(global_coords{-123, 511, 5}.chunk() == chunk_coords{-8, 31});
 
+static_assert(chunk_coords_{(short)100, (short)200, (char)300} + Vector3i(1, 2, 3) == chunk_coords_{(short)101, (short)202, (char)303});
+static_assert(chunk_coords_{(short)101, (short)202, (char)303} - Vector3i(1, 2, 3) == chunk_coords_{(short)100, (short)200, (char)300});
+
+static_assert(chunk_coords_{(short)100, (short)200, (char)300} + Vector2i(1, 2) == chunk_coords_{(short)101, (short)202, (char)300});
+static_assert(chunk_coords_{(short)101, (short)202, (char)300} - Vector2i(1, 2) == chunk_coords_{(short)100, (short)200, (char)300});
+
 } // namespace floormat
diff --git a/src/global-coords.hpp b/src/global-coords.hpp
index b3681992..6d8e1525 100644
--- a/src/global-coords.hpp
+++ b/src/global-coords.hpp
@@ -1,6 +1,7 @@
 #pragma once
 #include "local-coords.hpp"
 #include "compat/assert.hpp"
+#include <concepts>
 #include <Magnum/Magnum.h>
 #include <Magnum/Math/Vector2.h>
 #include <Magnum/Math/Vector3.h>
@@ -11,7 +12,6 @@ struct chunk_coords final {
     int16_t x = 0, y = 0;
 
     constexpr bool operator==(const chunk_coords& other) const noexcept = default;
-    constexpr Vector2i operator-(chunk_coords other) const noexcept;
 
     template<typename T>
     requires (std::is_floating_point_v<T> || std::is_integral_v<T> && (sizeof(T) > sizeof(x) || std::is_same_v<T, std::decay_t<decltype(x)>>))
@@ -22,11 +22,6 @@ struct chunk_coords final {
     explicit constexpr operator Math::Vector3<T>() const noexcept { return Math::Vector3<T>(T(x), T(y), T(0)); }
 };
 
-constexpr Vector2i chunk_coords::operator-(chunk_coords other) const noexcept
-{
-    return { Int{x} - other.x, Int{y} - other.y };
-}
-
 struct chunk_coords_ final {
     int16_t x = 0, y = 0;
     int8_t z = 0;
@@ -35,6 +30,30 @@ struct chunk_coords_ final {
     constexpr chunk_coords_(int16_t x, int16_t y, int8_t z) noexcept : x{x}, y{y}, z{z} {}
     constexpr chunk_coords_(chunk_coords c, int8_t z) noexcept : x{c.x}, y{c.y}, z{z} {}
     constexpr bool operator==(const chunk_coords_&) const noexcept = default;
+
+    template<std::integral T> constexpr chunk_coords_ operator+(Math::Vector2<T> off) const noexcept {
+        return { int16_t(x + int{off.x()}), int16_t(y + int{off.y()}), z };
+    }
+
+    template<std::integral T> constexpr chunk_coords_ operator-(Math::Vector2<T> off) const noexcept {
+        return { int16_t(x - int{off.x()}), int16_t(y - int{off.y()}), z };
+    }
+
+    template<std::integral T> constexpr chunk_coords_ operator+(Math::Vector3<T> off) const noexcept {
+        return { int16_t(x + int{off.x()}), int16_t(y + int{off.y()}), int8_t(z + int{off.z()}) };
+    }
+
+    template<std::integral T> constexpr chunk_coords_ operator-(Math::Vector3<T> off) const noexcept {
+        return { int16_t(x - int{off.x()}), int16_t(y - int{off.y()}), int8_t(z - int{off.z()}) };
+    }
+
+    template<std::integral T> constexpr chunk_coords_& operator+=(Math::Vector2<T> off) noexcept {
+        x = int16_t(x + int{off.x()}); y = int16_t(y + int{off.y()}); z = int8_t(z + off.z()); return *this;
+    }
+
+    template<std::integral T> constexpr chunk_coords_& operator-=(Math::Vector2<T> off) noexcept {
+        x = int16_t(x - int{off.x()}); y = int16_t(y - int{off.y()}); z = int8_t(z - off.z()); return *this;
+    }
 };
 
 constexpr inline int8_t chunk_z_min = -1, chunk_z_max = 14;
diff --git a/src/world.cpp b/src/world.cpp
index 9c3f8276..6749210a 100644
--- a/src/world.cpp
+++ b/src/world.cpp
@@ -199,4 +199,15 @@ void world::throw_on_wrong_entity_type(object_id id, entity_type actual, entity_
     fm_throw("object '{}' has wrong entity type '{}', should be '{}'"_cf, id, (size_t)actual, (size_t)expected);
 }
 
+auto world::neighbors(floormat::chunk_coords_ coord) -> std::array<neighbor_pair, 8>
+{
+    std::array<neighbor_pair, 8> ret;
+    for (auto i = 0uz; const auto& x : neighbor_offsets)
+    {
+        auto ch = coord + x;
+        ret[i++] = { at(ch), ch };
+    }
+    return ret;
+}
+
 } // namespace floormat
diff --git a/src/world.hpp b/src/world.hpp
index c4231173..4871a62c 100644
--- a/src/world.hpp
+++ b/src/world.hpp
@@ -97,6 +97,14 @@ public:
     [[nodiscard]] object_id make_id() { return ++_entity_counter; }
     void set_entity_counter(object_id value);
 
+    struct neighbor_pair final { chunk* c; chunk_coords_ coord; };
+
+    std::array<neighbor_pair, 8> neighbors(chunk_coords_ coord);
+
+    static constexpr std::array<Vector2b, 8> neighbor_offsets = {{
+        {-1, -1}, {-1,  0}, { 0, -1}, { 1,  1}, { 1,  0}, { 0,  1}, { 1, -1}, {-1,  1},
+    }};
+
     world& operator=(world&& w) noexcept;
     world(world&& w) noexcept;