diff --git a/lib/ecs/src/lib.rs b/lib/ecs/src/lib.rs
index 95493f9..08031f3 100644
--- a/lib/ecs/src/lib.rs
+++ b/lib/ecs/src/lib.rs
@@ -7,7 +7,12 @@ pub mod system;
 pub mod world;
 
 pub use component::Component as Component;
+pub use component::Resource as Resource;
 pub use world::World as World;
 pub use world::ReadData as ReadData;
+pub use world::ReadWriteData as ReadWriteData;
+pub use world::ReadResource as ReadResource;
+pub use world::ReadWriteResource as ReadWriteResource;
 pub use system::System as System;
 pub use system::Join as Join;
+pub use system::Processor as Processor;
diff --git a/lib/ecs/src/resourcemap.rs b/lib/ecs/src/resourcemap.rs
index 26dbca8..8c8beb5 100644
--- a/lib/ecs/src/resourcemap.rs
+++ b/lib/ecs/src/resourcemap.rs
@@ -1,6 +1,6 @@
 use std::cell::{Cell, UnsafeCell};
 use std::collections::BTreeMap;
-use std::ops::Deref;
+use std::ops::{Deref, DerefMut};
 
 use crate::component;
 use crate::borrow;
@@ -45,9 +45,35 @@ impl ResourceMap {
                                 None => Err(AccessError::concurrent()),
                                 Some(b2) => {
                                     let val = val.as_ref();
-                                    let val = unsafe { & *(val as *const (dyn component::Resource) as *const T) };
+                                    let val = & *(val as *const (dyn component::Resource) as *const T);
                                     drop(b);
-                                    Ok(ResourceRef { val, borrow: b2 })
+                                    Ok(ResourceRef { val, borrow: Some(b2) })
+                                },
+                            }
+                        },
+                        None => Err(AccessError("resource absent from world".to_string())),
+                    }
+                }
+            }
+        }
+    }
+
+    pub fn get_mut<'a, T: component::Resource>(&'a self) -> Result<ResourceRefMut<'a, T>, AccessError> {
+        match borrow::RefMut::new(&self.borrow) {
+            None => Err(AccessError::concurrent()),
+            Some(b) => {
+                let map = self.value.get();
+                unsafe {
+                    match (*map).get_mut(&component::resource_id::<T>()) {
+                        Some(entry) => {
+                            let val = &mut entry.resource;
+                            match borrow::RefMut::new(&entry.borrow) {
+                                None => Err(AccessError::concurrent()),
+                                Some(b2) => {
+                                    let val = val.as_mut();
+                                    let val = &mut *(val as *mut (dyn component::Resource) as *mut T);
+                                    drop(b);
+                                    Ok(ResourceRefMut { val, borrow: Some(b2) })
                                 },
                             }
                         },
@@ -92,7 +118,7 @@ impl ResourceMap {
 
 pub struct ResourceRef<'a, T: component::Resource> {
     val: *const T,
-    borrow: borrow::Ref<'a>,
+    borrow: Option<borrow::Ref<'a>>,
 }
 
 impl<'a, T: component::Resource> Deref for ResourceRef<'a, T> {
@@ -104,3 +130,37 @@ impl<'a, T: component::Resource> Deref for ResourceRef<'a, T> {
         }
     }
 }
+
+impl <'a, T: component::Resource> Drop for ResourceRef<'a, T> {
+    fn drop(&mut self) {
+        self.borrow = None;
+    }
+}
+
+pub struct ResourceRefMut<'a, T: component::Resource> {
+    val: *mut T,
+    borrow: Option<borrow::RefMut<'a>>,
+}
+
+impl <'a, T: component::Resource> Drop for ResourceRefMut<'a, T> {
+    fn drop(&mut self) {
+        self.borrow = None;
+    }
+}
+
+impl <'a, T: component::Resource> Deref for ResourceRefMut<'a, T> {
+    type Target = T;
+    fn deref(&self) -> &Self::Target {
+        unsafe {
+            &(*self.val)
+        }
+    }
+}
+
+impl <'a, T: component::Resource> DerefMut for ResourceRefMut<'a, T> {
+    fn deref_mut(&mut self) -> &mut Self::Target {
+        unsafe {
+            &mut(*self.val)
+        }
+    }
+}
diff --git a/lib/ecs/src/system.rs b/lib/ecs/src/system.rs
index f2dcf0d..5fdf3cf 100644
--- a/lib/ecs/src/system.rs
+++ b/lib/ecs/src/system.rs
@@ -6,7 +6,7 @@ use crate::{
     world::{
         ReadData, ReadDataIter,
         ReadWriteData, ReadWriteDataIter,
-        ReadResource,
+        ReadResource, ReadWriteResource,
         World,
     }
 };
@@ -75,6 +75,12 @@ impl<'a, T: component::Resource> Access<'a> for ReadResource<'a, T> {
     }
 }
 
+impl<'a, T: component::Resource> Access<'a> for ReadWriteResource<'a, T> {
+    fn fetch(world: &'a World) -> Self {
+        world.resource_mut()
+    }
+}
+
 impl <'a,
     T: Access<'a>,
     U: Access<'a>,
@@ -101,12 +107,34 @@ impl <'a,
     }
 }
 
+impl <'a,
+    T: Access<'a>,
+    U: Access<'a>,
+    V: Access<'a>,
+    W: Access<'a>,
+> Access<'a> for (T, U, V, W) {
+    fn fetch(world: &'a  World) -> Self {
+        (
+            T::fetch(world),
+            U::fetch(world),
+            V::fetch(world),
+            W::fetch(world),
+        )
+    }
+}
+
 pub struct Processor<'a> {
     world: &'a  World,
     runners: Vec<Box<dyn WorldRunner<'a>>>,
 }
 
 impl<'a> Processor<'a> {
+    pub fn new(world: &'a World) -> Self {
+        Self {
+            world,
+            runners: Vec::new(),
+        }
+    }
     pub fn add_system<T: System<'a> + 'static>(&mut self, system: T) {
         self.runners.push(Box::new(system));
     }
@@ -172,13 +200,19 @@ mod test {
         component::Resource,
         system,
         system::Join,
-        world::{ReadData, ReadWriteData, ReadResource, World},
+        world::{ReadData, ReadWriteData, ReadResource, ReadWriteResource, World},
     };
 
     #[derive(Clone,Debug,Default)]
     struct Delta(f32);
     impl Resource for Delta {}
 
+    #[derive(Clone,Debug)]
+    struct PhysicsStatus {
+        object_count: u64,
+    }
+    impl Resource for PhysicsStatus {}
+
     #[derive(Clone,Debug)]
     struct Position {
         x: f32,
@@ -199,15 +233,19 @@ mod test {
     impl<'a> system::System<'a> for Physics {
         type SystemData = ( ReadWriteData<'a, Position>
                           , ReadData<'a, Velocity>
-                          , ReadResource<'a, Delta>);
+                          , ReadResource<'a, Delta>
+                          , ReadWriteResource<'a, PhysicsStatus>);
 
-        fn run(&mut self, (pos, vel, delta): Self::SystemData) {
+        fn run(&mut self, (pos, vel, delta, status): Self::SystemData) {
             let d = delta.get();
+            let mut count = 0u64;
             for (mut p, v) in (pos, vel).join_all() {
                 p.x += v.x * d.0;
                 p.y += v.y * d.0;
                 p.z += v.z * d.0;
+                count += 1;
             }
+            status.get().object_count = count;
         }
     }
 
@@ -217,6 +255,7 @@ mod test {
         world.new_entity().with(Velocity { x: 0.0, y: 0.0, z: 1.0 }).with(Position { x: 1.0, y: 2.0, z: 3.0 }).build();
         world.new_entity().with(Velocity { x: 0.0, y: 0.0, z: 2.0 }).with(Position { x: 4.0, y: 5.0, z: 6.0 }).build();
         world.set_resource(Delta(1.0));
+        world.set_resource(PhysicsStatus { object_count: 0u64 });
 
         let mut p = system::Processor {
             world: &world,
@@ -231,5 +270,6 @@ mod test {
         world.set_resource(Delta(2.0));
         p.run();
         assert_eq!(vec![6.0, 12.0],  positions.iter().map(|(_, el)| el.z).collect::<Vec<f32>>());
+        assert_eq!(2, world.resource::<PhysicsStatus>().get().object_count);
     }
 }
diff --git a/lib/ecs/src/world.rs b/lib/ecs/src/world.rs
index 9237d4d..d9d99a4 100644
--- a/lib/ecs/src/world.rs
+++ b/lib/ecs/src/world.rs
@@ -1,7 +1,6 @@
 use std::collections::BTreeMap;
 use std::marker::PhantomData;
 use std::iter::Iterator;
-use std::cell::{Ref, RefMut, RefCell};
 
 use crate::componentmap::{
     ComponentMap,
@@ -11,6 +10,7 @@ use crate::componentmap::{
 use crate::resourcemap::{
     ResourceMap,
     ResourceRef,
+    ResourceRefMut,
 };
 use crate::entity;
 use crate::component;
@@ -98,7 +98,18 @@ pub struct ReadResource<'a, T: component::Resource> {
 
 impl<'a, T: component::Resource> ReadResource<'a, T> {
     pub fn get(&self) -> ResourceRef<'a, T> {
-        self.world.resources.get::<'a, T>().unwrap()
+        self.world.resources.get::<T>().unwrap()
+    }
+}
+
+pub struct ReadWriteResource<'a, T: component::Resource> {
+    world: &'a World,
+    phantom: PhantomData<&'a T>,
+}
+
+impl<'a, T: component::Resource> ReadWriteResource<'a, T> {
+    pub fn get(&self) -> ResourceRefMut<'a, T> {
+        self.world.resources.get_mut::<T>().unwrap()
     }
 }
 
@@ -154,6 +165,13 @@ impl World {
         }
     }
 
+    pub fn resource_mut<'a, T: component::Resource>(&'a self) -> ReadWriteResource<'a, T> {
+        ReadWriteResource {
+            world: self,
+            phantom: PhantomData,
+        }
+    }
+
     pub fn set_resource<T: component::Resource>(&self, r: T) {
         self.resources.set(r).unwrap();
     }