Switch to replicon (#80)

crates/shared/src/tick.rs

@@ -0,0 +1,17 @@
+use crate::GameState;
+use bevy::prelude::*;
+
+pub fn plugin(app: &mut App) {
+    app.init_resource::<GameTick>();
+
+    app.add_systems(
+        FixedLast,
+        (|mut tick: ResMut<GameTick>| {
+            tick.0 += 1;
+        })
+        .run_if(in_state(GameState::Playing)),
+    );
+}
+
+#[derive(Default, Resource)]
+pub struct GameTick(pub u64);