diff --git a/crates/border-wars/src/map/generation.rs b/crates/border-wars/src/map/generation.rs
index f1ce9ee..4f9088e 100644
--- a/crates/border-wars/src/map/generation.rs
+++ b/crates/border-wars/src/map/generation.rs
@@ -2,6 +2,7 @@
 
 use bevy::prelude::*;
 use noise::{NoiseFn, Perlin};
+use serde::{Deserialize, Serialize};
 
 use super::hex::*;
 use super::{Tile, TilePosition};
@@ -25,7 +26,7 @@ impl Plugin for MapGenerationPlugin {
 }
 
 /// An event to trigger the generation of the map.
-#[derive(Event)]
+#[derive(Event, Serialize, Deserialize, Clone, Copy)]
 pub struct StartMapGeneration {
     /// The seed used to generate the map.
     pub seed: u32,
diff --git a/crates/border-wars/src/networking/mod.rs b/crates/border-wars/src/networking/mod.rs
index e3f4f8a..a58c6ad 100644
--- a/crates/border-wars/src/networking/mod.rs
+++ b/crates/border-wars/src/networking/mod.rs
@@ -1,10 +1,12 @@
 //! All the code related to the networking.
 
-use bevnet::NetworkPlugin;
+use bevnet::{NetworkAppExt, NetworkPlugin, Receive};
 use bevy::prelude::*;
 use serde::{Deserialize, Serialize};
 
 use self::connection::ConnectionPlugin;
+use crate::map::generation::StartMapGeneration;
+use crate::CurrentScene;
 
 pub mod connection;
 
@@ -14,7 +16,9 @@ pub struct NetworkingPlugin;
 impl Plugin for NetworkingPlugin {
     fn build(&self, app: &mut App) {
         app.add_plugins(NetworkPlugin::new("relay.cocosol.fr".to_string()))
-            .add_plugins(ConnectionPlugin);
+            .add_plugins(ConnectionPlugin)
+            .add_systems(Update, start_game)
+            .add_network_event::<StartGame>();
     }
 }
 
@@ -30,3 +34,19 @@ pub enum PlayerRank {
     /// The player. He can join the game and play.
     Player,
 }
+
+/// TODO
+#[derive(Event, Serialize, Deserialize)]
+pub struct StartGame(pub StartMapGeneration);
+
+/// TODO
+fn start_game(
+    mut next_stats: ResMut<NextState<CurrentScene>>,
+    mut start_game_events: EventReader<Receive<StartGame>>,
+    mut start_map_generation_writer: EventWriter<StartMapGeneration>,
+) {
+    for event in start_game_events.read() {
+        next_stats.set(CurrentScene::Game);
+        start_map_generation_writer.send(event.1.0);
+    }
+}
diff --git a/crates/border-wars/src/scenes/lobby.rs b/crates/border-wars/src/scenes/lobby.rs
index 89201c9..d396cee 100644
--- a/crates/border-wars/src/scenes/lobby.rs
+++ b/crates/border-wars/src/scenes/lobby.rs
@@ -4,8 +4,9 @@ use bevnet::{Connection, SendTo};
 use bevy::prelude::*;
 use bevy_egui::{egui, EguiContexts};
 
+use crate::map::generation::StartMapGeneration;
 use crate::networking::connection::RemovePlayer;
-use crate::networking::PlayerRank;
+use crate::networking::{PlayerRank, StartGame};
 use crate::{CurrentScene, Player};
 
 /// The plugin for the lobby.
@@ -20,10 +21,11 @@ impl Plugin for LobbyPlugin {
 /// Display the UI of the lobby.
 fn lobby_ui(
     mut ctx: EguiContexts,
-    mut next_scene: ResMut<NextState<CurrentScene>>,
     connection: Res<Connection>,
     all_players_query: Query<&Player>,
     mut kick_player: EventWriter<SendTo<RemovePlayer>>,
+    mut map_size: Local<u32>,
+    mut start_game_event: EventWriter<SendTo<StartGame>>,
 ) {
     // Get our player info.
     let Some(self_player) = all_players_query
@@ -63,9 +65,22 @@ fn lobby_ui(
             ui.separator();
         }
 
-        if self_player.rank == PlayerRank::Admin && ui.button("Run the game").clicked() {
-            next_scene.set(CurrentScene::Game);
-            // TODO: run the game
+        if self_player.rank != PlayerRank::Admin {
+            return;
+        }
+
+        ui.add(egui::Slider::new(&mut (*map_size), 0..=10).text("map size"));
+
+        if ui.button("Run the game").clicked() {
+            for player in all_players_query.iter() {
+                start_game_event.send(SendTo(
+                    player.uuid,
+                    StartGame(StartMapGeneration {
+                        seed: 0,
+                        radius: 10,
+                    }),
+                ));
+            }
         }
     });
 }