diff --git a/agent.cc b/agent.cc
index 0688e00..4f016e1 100644
--- a/agent.cc
+++ b/agent.cc
@@ -42,6 +42,7 @@ agent::on_action_takes(void)
 void
 agent::on_tick(void)
 {
+	energy += world::sun_energy;
 }
 
 void
diff --git a/world.h b/world.h
index 41d91f4..dbfad88 100644
--- a/world.h
+++ b/world.h
@@ -4,6 +4,7 @@
 struct world {
 	const static int newborn_energy = 500;
 	const static int move_cost = 10;
+	const static int sun_energy = 1;
 };
 
 #endif