diff --git a/ppb/assets.py b/ppb/assets.py
index 71841a10..60a03200 100644
--- a/ppb/assets.py
+++ b/ppb/assets.py
@@ -7,6 +7,7 @@
 import threading
 
 import ppb.vfs as vfs
+import ppb.events as events
 from ppb.systemslib import System
 
 __all__ = 'Asset', 'AssetLoadingSystem',
@@ -58,10 +59,14 @@ def _finished_background(self, fut):
                 if hasattr(self, 'file_missing'):
                     logger.warning("File not found: %r", self.name)
                     self._data = self.file_missing()
+                    if _finished is not None:
+                        _finished(self)
                 else:
                     raise
             else:
                 self._data = self.background_parse(raw)
+                if _finished is not None:
+                    _finished(self)
         except Exception as exc:
             # Save unhandled exceptions to be raised in the main thread
             self._raise_error = exc
@@ -101,15 +106,18 @@ def load(self, timeout: float = None):
 
 
 class AssetLoadingSystem(System):
-    def __init__(self, **_):
+    def __init__(self, *, engine, **_):
+        super().__init__(**_)
+        self.engine = engine
         self._executor = concurrent.futures.ThreadPoolExecutor()
         self._queue = {}  # maps names to futures
 
     def __enter__(self):
         # 1. Register ourselves as the hint provider
-        global _hint, _backlog
+        global _hint, _finished, _backlog
         assert _hint is _default_hint
         _hint = self._hint
+        _finished = self._finished
 
         # 2. Grab-n-clear the backlog (atomically?)
         queue, _backlog = _backlog, []
@@ -134,6 +142,17 @@ def _load(filename):
         with vfs.open(filename) as file:
             return file.read()
 
+    def _finished(self, asset):
+        statuses = [
+            fut.running()
+            for fut in self._queue.values()
+        ]
+        self.engine.signal(events.AssetLoaded(
+            asset=asset,
+            total_loaded=sum(not s for s in statuses),
+            total_queued=sum(s for s in statuses),
+        ))
+
 
 _backlog = []
 
@@ -143,3 +162,4 @@ def _default_hint(filename, callback=None):
 
 
 _hint = _default_hint
+_finished = None
diff --git a/ppb/engine.py b/ppb/engine.py
index 6929439f..a9c5f282 100644
--- a/ppb/engine.py
+++ b/ppb/engine.py
@@ -10,7 +10,7 @@
 from typing import Type
 from typing import Union
 
-import ppb.events as events
+from ppb import events
 from ppb.eventlib import EventMixin
 from ppb.systems import EventPoller
 from ppb.systems import Renderer
@@ -114,6 +114,11 @@ def activate(self, next_scene: dict):
         self.scenes.append(scene(*args, **kwargs))
 
     def signal(self, event):
+        """
+        Add an event to the event queue.
+
+        Thread-safe.
+        """
         self.events.append(event)
 
     def publish(self):
diff --git a/ppb/events.py b/ppb/events.py
index 10d0b822..062cd062 100644
--- a/ppb/events.py
+++ b/ppb/events.py
@@ -22,6 +22,7 @@
     'SceneStopped',
     'StopScene',
     'Update',
+    'AssetLoaded',
 )
 
 # Remember to define scene at the end so the pargs version of __init__() still works
@@ -232,3 +233,16 @@ class Update:
     """
     time_delta: float
     scene: BaseScene = None
+
+
+import ppb
+
+
+@dataclass
+class AssetLoaded:
+    """
+    Fired whenever an asset finished loading.
+    """
+    asset: 'ppb.assets.Asset'
+    total_loaded: int
+    total_queued: int
diff --git a/ppb/sprites.py b/ppb/sprites.py
index 9dd6802d..bf085ab4 100644
--- a/ppb/sprites.py
+++ b/ppb/sprites.py
@@ -2,13 +2,13 @@
 from pathlib import Path
 from typing import Union
 
+import ppb_vector
+from ppb_vector import Vector
+
 import ppb
-from ppb import Vector
 from ppb.eventlib import EventMixin
 from ppb.utils import FauxFloat
 
-import ppb_vector
-
 
 TOP = "top"
 BOTTOM = "bottom"
diff --git a/ppb/systems/inputs.py b/ppb/systems/inputs.py
index be501a78..49418628 100644
--- a/ppb/systems/inputs.py
+++ b/ppb/systems/inputs.py
@@ -2,6 +2,7 @@
 
 import pygame
 
+from ppb import buttons
 import ppb.buttons as buttons
 from ppb_vector import Vector
 import ppb.events as events
diff --git a/ppb/systemslib.py b/ppb/systemslib.py
index e4481211..ef827993 100644
--- a/ppb/systemslib.py
+++ b/ppb/systemslib.py
@@ -1,4 +1,4 @@
-import ppb.eventlib as eventlib
+from ppb import eventlib
 
 
 class System(eventlib.EventMixin):
diff --git a/tests/test_assets.py b/tests/test_assets.py
index 94860d45..15cc03a9 100644
--- a/tests/test_assets.py
+++ b/tests/test_assets.py
@@ -1,16 +1,44 @@
 import pytest
 
 from ppb import GameEngine, BaseScene
+import ppb.events
+import ppb.assets
 from ppb.assets import Asset, AssetLoadingSystem
+from ppb.testutils import Failer
 
 
-def test_loading():
+@pytest.fixture
+def clean_assets():
+    """
+    Cleans out the global state of the asset system, so that we start fresh every
+    test.
+    """
+    ppb.assets._backlog = []
+
+
+class AssetTestScene(BaseScene):
+    def on_asset_loaded(self, event, signal):
+        self.ale = event
+        signal(ppb.events.Quit())
+
+
+def test_loading(clean_assets):
     a = Asset('ppb/engine.py')
-    engine = GameEngine(BaseScene, basic_systems=[AssetLoadingSystem])
+    engine = GameEngine(
+        AssetTestScene, basic_systems=[AssetLoadingSystem, Failer],
+        fail=lambda e: False, message=None, run_time=1,
+    )
     with engine:
         engine.start()
+        ats = engine.current_scene
+
+        engine.main_loop()
 
         assert a.load()
+        print(vars(ats))
+        assert ats.ale.asset is a
+        assert ats.ale.total_loaded == 1
+        assert ats.ale.total_queued == 0
 
 
 # def test_loading_root():
@@ -22,9 +50,12 @@ def test_loading():
 #         assert a.load()
 
 
-def test_missing_package():
+def test_missing_package(clean_assets):
     a = Asset('does/not/exist')
-    engine = GameEngine(BaseScene, basic_systems=[AssetLoadingSystem])
+    engine = GameEngine(
+        AssetTestScene, basic_systems=[AssetLoadingSystem, Failer],
+        fail=lambda e: False, message=None, run_time=1,
+    )
     with engine:
         engine.start()
 
@@ -32,9 +63,12 @@ def test_missing_package():
             assert a.load()
 
 
-def test_missing_resource():
+def test_missing_resource(clean_assets):
     a = Asset('ppb/dont.touch.this')
-    engine = GameEngine(BaseScene, basic_systems=[AssetLoadingSystem])
+    engine = GameEngine(
+        AssetTestScene, basic_systems=[AssetLoadingSystem, Failer],
+        fail=lambda e: False, message=None, run_time=1,
+    )
     with engine:
         engine.start()
 
@@ -42,26 +76,32 @@ def test_missing_resource():
             assert a.load()
 
 
-def test_parsing():
+def test_parsing(clean_assets):
     class Const(Asset):
         def background_parse(self, data):
             return "nah"
 
     a = Const('ppb/flags.py')
-    engine = GameEngine(BaseScene, basic_systems=[AssetLoadingSystem])
+    engine = GameEngine(
+        AssetTestScene, basic_systems=[AssetLoadingSystem, Failer],
+        fail=lambda e: False, message=None, run_time=1,
+    )
     with engine:
         engine.start()
 
         assert a.load() == "nah"
 
 
-def test_missing_parse():
+def test_missing_parse(clean_assets):
     class Const(Asset):
         def file_missing(self):
             return "igotu"
 
     a = Const('spam/eggs')
-    engine = GameEngine(BaseScene, basic_systems=[AssetLoadingSystem])
+    engine = GameEngine(
+        AssetTestScene, basic_systems=[AssetLoadingSystem, Failer],
+        fail=lambda e: False, message=None, run_time=1,
+    )
     with engine:
         engine.start()
 
diff --git a/viztests/README.md b/viztests/README.md
new file mode 100644
index 00000000..a781e9fe
--- /dev/null
+++ b/viztests/README.md
@@ -0,0 +1,7 @@
+Visual Tests
+============
+
+This is a test suite of manual tests, meant to help with the difficulty of
+thorough automated testing of graphical software.
+
+Run with `python -m viztests`
diff --git a/viztests/__main__.py b/viztests/__main__.py
new file mode 100644
index 00000000..ef3dad70
--- /dev/null
+++ b/viztests/__main__.py
@@ -0,0 +1,24 @@
+import ast
+from pathlib import Path
+import subprocess
+import sys
+
+
+def get_docstring(path):
+    tree = ast.parse(path.read_text(), path.name, mode='exec')
+
+    return ast.get_docstring(tree)
+
+
+for script in Path(__file__).resolve().parent.glob('*.py'):
+    if script.name.startswith('_'):
+        continue
+    ds = get_docstring(script)
+    print("=" * len(script.name))
+    print(script.name)
+    print("=" * len(script.name))
+    print("")
+    if ds is not None:
+        print(ds)
+        print("")
+    subprocess.run([sys.executable, str(script)], check=True)
diff --git a/viztests/angles.py b/viztests/angles.py
new file mode 100644
index 00000000..a8a21b6a
--- /dev/null
+++ b/viztests/angles.py
@@ -0,0 +1,31 @@
+"""
+Tests rotation vs Vector angles
+
+The center sprite should always face the orbiting sprite
+"""
+import ppb
+
+ROTATION_RATE = 90
+
+
+class CenterSprite(ppb.BaseSprite):
+    image = ppb.Image('player.png')
+
+    def on_update(self, event, signal):
+        self.rotation += ROTATION_RATE * event.time_delta
+
+
+class OrbitSprite(ppb.BaseSprite):
+    position = ppb.Vector(0, -2)
+    image = ppb.Image('target.png')
+
+    def on_update(self, event, signal):
+        self.position = self.position.rotate(ROTATION_RATE * event.time_delta)
+
+
+def setup(scene):
+    scene.add(CenterSprite())
+    scene.add(OrbitSprite())
+
+
+ppb.run(setup)
diff --git a/viztests/bullet.png b/viztests/bullet.png
new file mode 100755
index 00000000..b5a8a035
Binary files /dev/null and b/viztests/bullet.png differ
diff --git a/viztests/player.png b/viztests/player.png
new file mode 100755
index 00000000..e168d251
Binary files /dev/null and b/viztests/player.png differ
diff --git a/viztests/target.png b/viztests/target.png
new file mode 100644
index 00000000..841309db
Binary files /dev/null and b/viztests/target.png differ