diff -r a4dd3d307115 -r a4c17cfaa4c9 rust/hwphysics/src/grid.rs
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rust/hwphysics/src/grid.rs	Fri Nov 09 01:05:34 2018 +0300
@@ -0,0 +1,91 @@
+use crate::{
+    common::GearId,
+    collision::{
+        fppoint_round,
+        CircleBounds,
+        DetectedCollisions
+    }
+};
+
+use integral_geometry::{
+    Point,
+    Size,
+    GridIndex
+};
+use fpnum::FPPoint;
+
+struct GridBin {
+    refs: Vec<GearId>,
+    static_entries: Vec<CircleBounds>,
+    dynamic_entries: Vec<CircleBounds>
+}
+
+impl GridBin {
+    fn new() -> Self {
+        Self {
+            refs: vec![],
+            static_entries: vec![],
+            dynamic_entries: vec![]
+        }
+    }
+}
+
+const GRID_BIN_SIZE: usize = 256;
+
+pub struct Grid {
+    bins: Vec<GridBin>,
+    space_size: Size,
+    bins_count: Size,
+    index: GridIndex
+}
+
+impl Grid {
+    pub fn new(size: Size) -> Self {
+        assert!(size.is_power_of_two());
+        let bins_count =
+            Size::new(size.width / GRID_BIN_SIZE,
+                      size.height / GRID_BIN_SIZE);
+
+        Self {
+            bins: (0..bins_count.area()).map(|_| GridBin::new()).collect(),
+            space_size: size,
+            bins_count,
+            index: Size::square(GRID_BIN_SIZE).to_grid_index()
+        }
+    }
+
+    fn bin_index(&self, position: &FPPoint) -> Point {
+        self.index.map(fppoint_round(position))
+    }
+
+    fn lookup_bin(&mut self, position: &FPPoint) -> &mut GridBin {
+        let index = self.bin_index(position);
+        &mut self.bins[index.x as usize * self.bins_count.width + index.y as usize]
+    }
+
+    pub fn insert_static(&mut self, gear_id: GearId, position: &FPPoint, bounds: &CircleBounds) {
+        self.lookup_bin(position).static_entries.push(*bounds)
+    }
+
+    pub fn insert_dynamic(&mut self, gear_id: GearId, position: &FPPoint, bounds: &CircleBounds) {
+        self.lookup_bin(position).dynamic_entries.push(*bounds)
+    }
+
+    pub fn check_collisions(&self, collisions: &mut DetectedCollisions) {
+        for bin in &self.bins {
+            for bounds in &bin.dynamic_entries {
+                for other in &bin.dynamic_entries {
+                    if bounds.intersects(other) && bounds != other {
+                        collisions.push(0, 0, &bounds.center)
+                    }
+                }
+
+                for other in &bin.static_entries {
+                    if bounds.intersects(other) {
+                        collisions.push(0, 0, &bounds.center)
+                    }
+                }
+            }
+        }
+    }
+}
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