diff --git a/src/game.zig b/src/game.zig
index 4a2d299..534ee7d 100644
--- a/src/game.zig
+++ b/src/game.zig
@@ -1,48 +1,90 @@
 const std = @import("std");
+const builtin = @import("builtin");
 const sdl = @import("sdl");
+const Graph = @import("graph.zig");
 const Graphics = @import("graphics.zig");
 
-graphics: Graphics,
-running: bool,
+// TODO:
+// - Do something about deallocating `Resource`s when `Graph` fails
+
+const RunInfo = struct { running: bool };
+
+alloc: std.mem.Allocator,
+graph: Graph,
 
 const Self = @This();
-pub fn init() GameError!Self {
+pub fn init(alloc: std.mem.Allocator) GameError!Self {
+    var graph = try Graph.init(alloc);
+    errdefer graph.deinit();
+
+    const graphics = try Graphics.create();
+
+    var controller = try graph.getController();
+    controller.addResource(graphics);
+    try graph.freeController(controller);
+
     return Self{
-        .graphics = try Graphics.create(),
-        .running = false,
+        .alloc = alloc,
+        .graph = graph,
     };
 }
 
 pub fn run(self: *Self) GameError!void {
-    self.running = true;
+    {
+        var controller = try self.graph.getController();
+        controller.addResource(RunInfo{ .running = true });
+        try self.graph.freeController(controller);
+    }
+
     while (true) {
-        try self.processEvents();
-        if (!self.running) {
+        if (!self.graph.getResource(RunInfo).?.running) {
             break;
         }
-        try self.update();
-        try self.draw();
+
+        var controller = try self.graph.getController();
+        controller.queue(.{
+            .events = processEvents,
+            .draw = draw,
+            .ordered = true,
+        });
+        try self.graph.freeController(controller);
+
+        defer self.graph.reset();
+        try self.graph.runAllSystems();
     }
 }
 
-fn update(self: *Self) GameError!void {
-    _ = self;
+fn draw(graphics: *Graphics) GameError!void {
+    try graphics.beginDraw();
+    {
+        errdefer graphics.endDraw() catch {};
+        try graphics.drawDebug();
+    }
+    try graphics.endDraw();
 }
 
-fn draw(self: *Self) GameError!void {
-    try self.graphics.beginDraw();
-    try self.graphics.drawDebug();
-    try self.graphics.endDraw();
+fn clean(graphics: *Graphics) !void {
+    graphics.destroy();
+    // TODO: Also remove the resource
 }
 
-fn processEvents(self: *Self) GameError!void {
+fn processEvents(graphics: *Graphics, run_info: *RunInfo) GameError!void {
     sdl.PumpEvents();
     while (true) {
         var buffer: [16]sdl.Event = undefined;
         const count: usize = @intCast(sdl.PeepEvents(&buffer, buffer.len, sdl.GETEVENT, sdl.EVENT_FIRST, sdl.EVENT_LAST));
         if (count == -1) return GameError.SdlError;
         for (buffer[0..count]) |event| {
-            self.processEvent(event);
+            switch (event.type) {
+                sdl.EVENT_QUIT => {
+                    run_info.running = false;
+                },
+                sdl.EVENT_WINDOW_RESIZED => {
+                    if (event.window.windowID != sdl.GetWindowID(graphics.window)) return;
+                    graphics.resize(@intCast(event.window.data1), @intCast(event.window.data2));
+                },
+                else => {},
+            }
         }
         if (count < buffer.len) {
             break;
@@ -51,25 +93,21 @@ fn processEvents(self: *Self) GameError!void {
     sdl.FlushEvents(sdl.EVENT_FIRST, sdl.EVENT_LAST);
 }
 
-fn processEvent(self: *Self, event: sdl.Event) void {
-    switch (event.type) {
-        sdl.EVENT_QUIT => {
-            self.running = false;
-        },
-        sdl.EVENT_WINDOW_RESIZED => {
-            if (event.window.windowID != sdl.GetWindowID(self.graphics.window)) return;
-            self.graphics.resize(@intCast(event.window.data1), @intCast(event.window.data2));
-        },
-        else => {},
-    }
-}
-
 pub fn deinit(self: *Self) void {
-    self.graphics.destroy();
+    var controller = self.graph.getController() catch unreachable;
+    controller.queue(clean);
+    self.graph.freeController(controller) catch unreachable;
+    self.graph.runAllSystems() catch unreachable;
+
+    self.graph.deinit();
+
     sdl.Quit();
 }
 
 pub const GameError = error{
     SdlError,
     OSError,
+    OutOfMemory,
+    MissingResource,
+    SystemDeadlock,
 };
diff --git a/src/graph.zig b/src/graph.zig
index d5c6c6d..438208e 100644
--- a/src/graph.zig
+++ b/src/graph.zig
@@ -8,6 +8,9 @@ const System = @import("graph/system.zig");
 // - Resolve missing resource problem
 // - Parse system sets into a properly defined data structure instead of relying on `@typeInfo`
 // - Find a better way to represent system sets
+// - Organize a better way to execute single commands on graph
+// - Handle system errors
+// - Removing of resources
 
 pub const Controller = @import("graph/controller.zig");
 
@@ -86,12 +89,40 @@ pub fn deinit(self: *Self) void {
     self.duds.deinit(self.alloc);
 }
 
+/// Clear all internal data in preparation for the next run cycle
+/// Does not clear any `Resource`s
+pub fn reset(self: *Self) void {
+    // Controller cleanup
+    for (self.controllers.items, 0..) |*controller, i| {
+        for (controller.commands()) |*command| {
+            switch (command.*) {
+                .add_resource => |*resource| resource.deinit(controller.alloc),
+                .queue_system => |*system| system.deinit(controller.alloc),
+            }
+        }
+        controller.clear();
+        controller.setDuds(
+            i * self.duds.items.len / self.controllers.items.len,
+            (i + 1) * self.duds.items.len / self.controllers.items.len,
+        );
+    }
+    // System cleanup
+    for (self.system_queue.items) |*system| {
+        system.deinit(self.alloc);
+    }
+    self.system_queue.clearRetainingCapacity();
+    // Duds cleanup
+    for (self.duds.items) |*dud| {
+        dud.required_count = 0;
+    }
+}
+
 fn enqueueSystem(self: *Self, system: System) !void {
     errdefer system.deinit(self.alloc);
     try self.system_queue.append(self.alloc, system);
 }
 
-fn runAllSystems(self: *Self) GraphError!void {
+pub fn runAllSystems(self: *Self) GraphError!void {
     while (self.system_queue.items.len > 0) {
         var swap_with = self.system_queue.items.len - 1;
 
@@ -169,7 +200,7 @@ fn applyCommands(self: *Self, commands: []const Controller.Command) !void {
     }
 }
 
-fn getController(self: *Self) !Controller {
+pub fn getController(self: *Self) !Controller {
     if (self.controllers.pop()) |c| {
         return c;
     }
@@ -185,7 +216,7 @@ fn getController(self: *Self) !Controller {
 }
 
 /// Evaluates and clears the controller (even if errors out)
-fn freeController(self: *Self, controller: Controller) !void {
+pub fn freeController(self: *Self, controller: Controller) !void {
     var c = controller;
     try self.applyCommands(c.commands());
     c.clear();
diff --git a/src/graph/controller.zig b/src/graph/controller.zig
index c0c2f50..c7fdc32 100644
--- a/src/graph/controller.zig
+++ b/src/graph/controller.zig
@@ -34,7 +34,7 @@ pub fn create(alloc: std.mem.Allocator) !Controller {
 
 /// Returns command queue, caller is responsible for freeing it's data
 /// Call `clean()` afterwards, to clear the command queue
-pub fn commands(self: *Controller) []const Command {
+pub fn commands(self: *Controller) []Command {
     return self.command_buffer.items;
 }
 
diff --git a/src/graph/system.zig b/src/graph/system.zig
index c49179b..fad1829 100644
--- a/src/graph/system.zig
+++ b/src/graph/system.zig
@@ -8,9 +8,9 @@ requires_dud: ?Dud.Id,
 submit_dud: ?Dud.Id,
 
 pub const Dud = struct {
-    pub const Id = u16;
+    pub const Id = usize;
 
-    required_count: usize = 0,
+    required_count: u16 = 0,
 };
 
 pub const Request = union(enum) {
diff --git a/src/graph/utils.zig b/src/graph/utils.zig
index 5124c07..fec06fe 100644
--- a/src/graph/utils.zig
+++ b/src/graph/utils.zig
@@ -32,7 +32,8 @@ pub fn validateResource(comptime resource_type: type) void {
 pub fn validateSystem(comptime system: anytype) void {
     const info = @typeInfo(@TypeOf(system));
     if (info != .@"fn") @compileError("System can only be a function, got " ++ @typeName(system));
-    if (info.@"fn".return_type != void) @compileError("Systems are not allowed to return any value (" ++ @typeName(info.Fn.return_type.?) ++ " returned)");
+    if (@typeInfo(info.@"fn".return_type.?) != .void and
+        @typeInfo(info.@"fn".return_type.?) != .error_union) @compileError("Systems are not allowed to return any value (" ++ @typeName(info.@"fn".return_type.?) ++ " returned)");
     if (info.@"fn".is_var_args) @compileError("System cannot be variadic");
     if (info.@"fn".is_generic) @compileError("System cannot be generic");
 
@@ -85,7 +86,13 @@ pub fn generateRunner(comptime system: anytype) fn ([]const *anyopaque) void {
             inline for (0..@typeInfo(@TypeOf(system)).@"fn".params.len) |index| {
                 args[index] = @alignCast(@ptrCast(resources[index]));
             }
-            @call(.always_inline, system, args);
+            switch (@typeInfo(@typeInfo(@TypeOf(system)).@"fn".return_type.?)) {
+                .void => @call(.always_inline, system, args),
+                .error_union => @call(.always_inline, system, args) catch |err| {
+                    std.debug.print("System error: {s}\n", .{@errorName(err)});
+                },
+                else => unreachable,
+            }
         }
     };
     return RunnerImpl.runner;
diff --git a/src/main.zig b/src/main.zig
index 00fa81a..c3211d5 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -1,9 +1,26 @@
 const std = @import("std");
+const builtin = @import("builtin");
 const sdl = @import("sdl");
 const Game = @import("game.zig");
 
 pub fn runGame() !void {
-    var game = try Game.init();
+    var allocator = switch (builtin.mode) {
+        .ReleaseSafe, .Debug => std.heap.DebugAllocator(.{}).init,
+        .ReleaseFast => std.heap.smp_allocator,
+        .ReleaseSmall => std.heap.c_allocator,
+    };
+    defer switch (builtin.mode) {
+        .ReleaseSafe, .Debug => std.debug.assert(allocator.deinit() == .ok),
+        else => {},
+    };
+
+    var game = try Game.init(
+        switch (builtin.mode) {
+            .ReleaseSafe, .Debug => allocator.allocator(),
+            .ReleaseFast => allocator,
+            .ReleaseSmall => allocator,
+        },
+    );
     defer game.deinit();
     try game.run();
 }