diff --git a/libs/phys/source/engine_2d.cpp b/libs/phys/source/engine_2d.cpp
index f0daf0fe..b15af8d9 100644
--- a/libs/phys/source/engine_2d.cpp
+++ b/libs/phys/source/engine_2d.cpp
@@ -8,8 +8,6 @@
 #include <psemek/geom/rotation.hpp>
 #include <psemek/geom/math.hpp>
 
-#include <psemek/util/profiler.hpp>
-
 #include <psemek/log/log.hpp>
 
 #include <optional>
@@ -415,13 +413,18 @@ namespace psemek::phys2d
 
 		std::optional<geom::vector<float, 2>> gravity;
 
+		std::set<contact, velocity_comparator> contacts_by_velocity;
+		std::set<contact, penetration_comparator> contacts_by_penetration;
+
 		void explode(geom::point<float, 2> const & center, float strength, float attenuation);
 
 		void update(float dt);
 
 		void apply_gravity(float dt);
 		void integrate(float dt);
-		void resolve_collisions();
+		void gather_collisions();
+		void resolve_impulses();
+		void resolve_penetrations();
 
 		void log_energy();
 		float energy();
@@ -446,7 +449,9 @@ namespace psemek::phys2d
 	{
 		apply_gravity(dt);
 		integrate(dt);
-		resolve_collisions();
+		gather_collisions();
+		resolve_impulses();
+		resolve_penetrations();
 //		log_energy();
 	}
 
@@ -478,7 +483,7 @@ namespace psemek::phys2d
 		}
 	}
 
-	void engine::impl::resolve_collisions()
+	void engine::impl::gather_collisions()
 	{
 		for (std::size_t gi = 0; gi < groups.size(); ++gi)
 		{
@@ -491,7 +496,8 @@ namespace psemek::phys2d
 			}
 		}
 
-		std::set<contact, velocity_comparator> contacts_by_velocity;
+		contacts_by_velocity.clear();
+		contacts_by_penetration.clear();
 
 		for (std::size_t gi = 0; gi < groups.size(); ++gi)
 		{
@@ -547,12 +553,13 @@ namespace psemek::phys2d
 				}
 			}
 		}
+	}
 
-		std::size_t const contact_count = contacts_by_velocity.size();
-		std::size_t const impulse_iterations = contact_count * 2;
-		std::size_t const penetraion_iterations = contact_count * 2;
+	void engine::impl::resolve_impulses()
+	{
+		std::size_t const iterations = contacts_by_velocity.size() * 2;
 
-		for (std::size_t iteration = 0; iteration < impulse_iterations; ++iteration)
+		for (std::size_t iteration = 0; iteration < iterations; ++iteration)
 		{
 			contact const & c = *contacts_by_velocity.begin();
 
@@ -711,9 +718,11 @@ namespace psemek::phys2d
 				groups[ccc.gj].contacts_by_velocity[ccc.j][ctj] = new_it;
 			}
 		}
+	}
 
-		std::set<contact, penetration_comparator> contacts_by_penetration;
 
+	void engine::impl::resolve_penetrations()
+	{
 		for (auto it = contacts_by_velocity.begin(); it != contacts_by_velocity.end();)
 		{
 			auto jt = it++;
@@ -726,9 +735,9 @@ namespace psemek::phys2d
 			groups[c.gj].contacts_by_penetration[c.j].push_back(new_it);
 		}
 
-		assert(contacts_by_penetration.size() == contact_count);
+		std::size_t const iterations = contacts_by_penetration.size() * 2;
 
-		for (std::size_t iteration = 0; iteration < penetraion_iterations; ++iteration)
+		for (std::size_t iteration = 0; iteration < iterations; ++iteration)
 		{
 			contact const & c = *contacts_by_penetration.begin();