--- a/Makefile	Tue Jan 14 19:51:18 2020 -0500
+++ b/Makefile	Sun Aug 29 14:41:27 2021 -0400
@@ -1,17 +1,12 @@
-.PHONY: pubdocs test-sbcl test-ccl test-ecl test vendor
+.PHONY: pubdocs test-sbcl test-ccl test-ecl test-abcl test
 
+heading_printer = $(shell which heading || echo 'true')
 sourcefiles = $(shell ffind --full-path --literal .lisp)
 docfiles = $(shell ls docs/*.markdown)
 apidoc = docs/03-reference.markdown
 
-# Vendor ----------------------------------------------------------------------
-vendor/quickutils.lisp: vendor/make-quickutils.lisp
-	cd vendor && sbcl --noinform --load make-quickutils.lisp  --eval '(quit)'
-
-vendor: vendor/quickutils.lisp
-
 # Documentation ---------------------------------------------------------------
-$(apidoc): $(sourcefiles) docs/api.lisp package.lisp
+$(apidoc): $(sourcefiles) docs/api.lisp
 	sbcl --noinform --load docs/api.lisp  --eval '(quit)'
 
 docs/build/index.html: $(docfiles) $(apidoc) docs/title
@@ -29,17 +24,17 @@
 test: test-sbcl test-ccl test-ecl test-abcl
 
 test-sbcl:
-	./test/header.sh computer 'SBCL'
-	ros run -L sbcl --load test/test-run.lisp
+	$(heading_printer) computer 'SBCL'
+	time sbcl --load test/run.lisp
 
 test-ccl:
-	./test/header.sh slant 'CCL'
-	ros run -L ccl-bin --load test/test-run.lisp
+	$(heading_printer) slant 'CCL'
+	time ccl --load test/run.lisp
 
 test-ecl:
-	./test/header.sh roman 'ECL'
-	ros run -L ecl --load test/test-run.lisp
+	$(heading_printer) roman 'ECL'
+	time ecl -load test/run.lisp
 
 test-abcl:
-	./test/header.sh broadway 'ABCL'
-	abcl --load test/test-run.lisp
+	$(heading_printer) broadway 'ABCL'
+	time abcl --load test/run.lisp
--- a/README.markdown	Tue Jan 14 19:51:18 2020 -0500
+++ b/README.markdown	Sun Aug 29 14:41:27 2021 -0400
@@ -26,7 +26,7 @@
 * **Mercurial:** <https://hg.stevelosh.com/beast/>
 * **Git:** <https://github.com/sjl/beast/>
 
-The test suite currently passes in SBCL, CCL, ECL, and ABCL on OS X and Debian.
+The test suite currently passes in SBCL, CCL, ECL, and ABCL on Ubuntu 20.04.
 Further testing is welcome.
 
 [quicklisp]: https://quicklisp.org/
--- a/beast-test.asd	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,11 +0,0 @@
-(asdf:defsystem :beast-test
-  :depends-on (:1am :beast)
-
-  :serial t
-  :components ((:file "package-test")
-               (:module "test"
-                :serial t
-                :components ((:file "test"))))
-
-  :perform
-  (asdf:test-op (op system) (uiop:symbol-call :beast-test :run-tests)))
--- a/beast.asd	Tue Jan 14 19:51:18 2020 -0500
+++ b/beast.asd	Sun Aug 29 14:41:27 2021 -0400
@@ -4,18 +4,27 @@
   :homepage "https://docs.stevelosh.com/beast/"
 
   :license "MIT"
-  :version "1.1.0"
+  :version "1.2.0"
 
   :depends-on ()
 
   :serial t
-  :components ((:module "vendor"
+  :components ((:module "src"
                 :serial t
-                :components ((:file "quickutils-package")
-                             (:file "quickutils")))
-               (:file "package")
-               (:module "src"
+                :components ((:file "package")
+                             (:file "main"))))
+
+  :in-order-to ((asdf:test-op (asdf:test-op :beast/test))))
+
+
+(asdf:defsystem :beast/test
+  :depends-on (:1am :beast)
+
+  :serial t
+  :components ((:module "test"
                 :serial t
-                :components ((:file "beast"))))
+                :components ((:file "package")
+                             (:file "test"))))
 
-  :in-order-to ((asdf:test-op (asdf:test-op :beast-test))))
+  :perform
+  (asdf:test-op (op system) (uiop:symbol-call :beast/test :run-tests)))
--- a/docs/03-reference.markdown	Tue Jan 14 19:51:18 2020 -0500
+++ b/docs/03-reference.markdown	Sun Aug 29 14:41:27 2021 -0400
@@ -12,6 +12,17 @@
 
 ## Package `BEAST`
 
+### `ALL-ENTITIES` (function)
+
+    (ALL-ENTITIES)
+
+Return a list of all entities.
+
+  Normally you should run code on entities using systems, but this function can
+  be handy for debugging purposes.
+
+  
+
 ### `CLEAR-ENTITIES` (function)
 
     (CLEAR-ENTITIES)
--- a/docs/04-changelog.markdown	Tue Jan 14 19:51:18 2020 -0500
+++ b/docs/04-changelog.markdown	Sun Aug 29 14:41:27 2021 -0400
@@ -5,6 +5,24 @@
 
 [TOC]
 
+v1.2.0
+------
+
+Refactored a chunk of the code to do a few things:
+
+1. Removed the (vendored) dependency on Quickutils.
+2. Removed dependency on Roswell for running unit tests.
+3. All system-running functions are expanded into `ARITY` nested loops, not just
+   those with arity 2 or smaller.
+4. Modernized the file/directory structure to match my recent projects.
+5. Added more unit tests to cover parts of the code that weren't being tested
+   before.
+6. The internal system argument indexes are now vectors instead of lists.
+7. Exported `all-entities` for debugging.
+
+Other than the new `all-entities` function nothing user-visible should have
+changed.  Please file a bug if you see any new or broken behavior.
+
 v1.1.0
 ------
 
--- a/docs/index.markdown	Tue Jan 14 19:51:18 2020 -0500
+++ b/docs/index.markdown	Sun Aug 29 14:41:27 2021 -0400
@@ -12,7 +12,7 @@
 * **Mercurial:** <https://hg.stevelosh.com/beast/>
 * **Git:** <https://github.com/sjl/beast/>
 
-The test suite currently passes in SBCL, CCL, ECL, and ABCL on OS X and Debian.
+The test suite currently passes in SBCL, CCL, ECL, and ABCL on Ubuntu 20.04.
 Further testing is welcome.
 
 [quicklisp]: https://quicklisp.org/
--- a/package-test.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,7 +0,0 @@
-(defpackage #:beast-test
-  (:use
-    #:cl
-    #:1am
-    #:beast)
-  (:export
-    #:run-tests))
--- a/package.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,21 +0,0 @@
-(defpackage :beast
-  (:use
-    :cl
-    :beast.quickutils)
-  (:export
-    :entity
-    :entity-id
-
-    :define-entity
-
-    :create-entity
-    :destroy-entity
-    :clear-entities
-    :map-entities
-
-    :entity-created
-    :entity-destroyed
-
-    :define-aspect
-
-    :define-system))
--- a/src/beast.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,359 +0,0 @@
-(in-package :beast)
-
-
-;;;; Notes
-;;; Entities are stored in an {id -> entity} hash table.
-;;;
-;;; Entities are also indexed by aspect in a nested hash table:
-;;;
-;;;     {aspect-symbol -> {id -> entity}}
-;;;
-;;; Entities are indexed by system too:
-;;;
-;;;     {system-symbol ->
-;;;         ({id -> entity}   ; arg1
-;;;          {id -> entity})  ; arg2
-;;;     }
-;;;
-;;; Systems are stored as:
-;;;
-;;;     {system-symbol -> (system-function arity type-specifier-list)}
-;;;
-;;; TODO: Figure out the distinct problem.
-
-
-;;;; Global Data Structures ---------------------------------------------------
-(defvar *entity-id-counter* 0)
-(defvar *entity-index* (make-hash-table))
-(defvar *aspect-index* (make-hash-table))
-(defvar *system-index* (make-hash-table))
-(defvar *systems* (make-hash-table))
-
-
-;;;; Entities -----------------------------------------------------------------
-(defclass entity ()
-  ((id
-     :reader entity-id :initform (incf *entity-id-counter*)
-     :documentation
-     "The unique ID of the entity.  This may go away in the future.")
-   (%beast/aspects
-     :allocation :class :initform nil
-     :documentation
-     "A list of the aspects this entity class inherits.  **Don't touch this.**"))
-  (:documentation "A single entity in the game world."))
-
-(defmethod print-object ((e entity) stream)
-  (print-unreadable-object (e stream :type t :identity nil)
-    (format stream "~D" (entity-id e))))
-
-
-(defun entity-satisfies-system-type-specifier-p (entity specifier)
-  (every (lambda (aspect) (typep entity aspect))
-         specifier))
-
-(defun index-entity (entity)
-  "Insert `entity` into the entity index."
-  (setf (gethash (entity-id entity) *entity-index*) entity))
-
-(defun index-entity-aspects (entity)
-  "Insert `entity` into appropriate aspect indexes."
-  (loop :for aspect :in (slot-value entity '%beast/aspects)
-        :do (setf (gethash (entity-id entity)
-                           (gethash aspect *aspect-index*))
-                  entity)))
-
-(defun index-entity-systems (entity)
-  "Insert `entity` into appropriate system indexes."
-  (loop
-    :with id = (entity-id entity)
-    :for system :being :the hash-keys :of *systems*
-    :using (hash-value (nil nil type-specifiers))
-    :do (loop :for argument-index :in (gethash system *system-index*)
-              :for specifier :in type-specifiers
-              :when (entity-satisfies-system-type-specifier-p entity specifier)
-              :do (setf (gethash id argument-index) entity))))
-
-
-(defun unindex-entity (id)
-  "Remove `entity` from the entity-level index."
-  (remhash id *entity-index*))
-
-(defun unindex-entity-aspects (id)
-  "Remove `entity` from the aspect indexes."
-  (loop
-    :for index :being :the hash-values :of *aspect-index*
-    :do (remhash id index)))
-
-(defun unindex-entity-systems (id)
-  "Remove `entity` from the system indexes."
-  (loop
-    :for argument-indexes :being :the hash-values :of *system-index*
-    :do (loop :for index :in argument-indexes
-              :do (remhash id index))))
-
-
-(defgeneric entity-created (entity)
-  (:method ((entity entity)) nil)
-  (:documentation
-  "Called after an entity has been created and indexed.
-
-  The default method does nothing, but users can implement their own auxillary
-  methods to run code when entities are created.
-
-  "))
-
-(defgeneric entity-destroyed (entity)
-  (:method ((entity entity)) nil)
-  (:documentation
-  "Called after an entity has been destroyed and unindexed.
-
-  The default method does nothing, but users can implement their own auxillary
-  methods to run code when entities are destroyed.
-
-  "))
-
-
-(defun create-entity (class &rest initargs)
-  "Create an entity of the given entity class and return it.
-
-  `initargs` will be passed along to `make-instance`.
-
-  The `entity-created` generic function will be called just before returning the
-  entity.
-
-  "
-  (let ((entity (apply #'make-instance class initargs)))
-    (index-entity entity)
-    (index-entity-aspects entity)
-    (index-entity-systems entity)
-    (entity-created entity)
-    entity))
-
-(defun destroy-entity (entity)
-  "Destroy `entity` and return it.
-
-  The `entity-destroyed` generic function will be called after the entity has
-  been destroyed and unindexed.
-
-  "
-  (let ((id (entity-id entity)))
-    (unindex-entity id)
-    (unindex-entity-aspects id)
-    (unindex-entity-systems id))
-  (entity-destroyed entity)
-  entity)
-
-(defun clear-entities ()
-  "Destroy all entities.
-
-  `destroy-entity` will be called for each entity.
-
-  Returns a list of all the destroyed entites.
-
-  "
-  (mapc #'destroy-entity (hash-table-values *entity-index*)))
-
-
-(defun get-entity (id)
-  "Return the entity with the given `id`, or `nil` if it is unknown."
-  (gethash id *entity-index*))
-
-(defun all-entities ()
-  "Return a list of all entities."
-  (hash-table-values *entity-index*))
-
-(defun map-entities (function &optional (type 'entity))
-  "Map `function` over all entities that are subtypes of `type`.
-
-  Normally you should run code on entities using systems, but this function can
-  be handy for debugging purposes.
-
-  "
-  (mapcar function
-          (remove-if-not (lambda (entity) (typep entity type))
-                         (hash-table-values *entity-index*))))
-
-
-(defmacro define-entity (name aspects &rest slots)
-  "Define an entity class.
-
-  `name` should be a symbol that will become the name of the class.
-
-  `aspects` should be a list of the aspects this entity should inherit from.
-
-  `slots` can be zero or more extra CLOS slot definitions.
-
-  Examples:
-
-    (define-entity potion (drinkable))
-
-    (define-entity cheese (edible visible)
-      (flavor :accessor cheese-flavor :initarg :flavor))
-
-  "
-  `(progn
-    (defclass ,name (entity ,@aspects)
-      ((%beast/aspects :allocation :class :initform ',aspects)
-       ,@slots))
-    (defun ,(symb name '?) (object)
-      (typep object ',name))
-    (find-class ',name)))
-
-
-;;;; Aspects ------------------------------------------------------------------
-(defun initialize-aspect-index (name)
-  (when (not (hash-table-key-exists-p *aspect-index* name))
-    (setf (gethash name *aspect-index*) (make-hash-table))))
-
-(defmacro define-aspect (name &rest fields)
-  "Define an aspect class.
-
-  `name` should be a symbol that will become the name of the class.
-
-  `fields` should be zero or more field definitions.  Each field definition can
-  be a symbol (the field name), or a list of the field name and extra CLOS slot
-  options.
-
-  Field names will have the aspect name and a slash prepended to them to create
-  the slot names.  `:initarg` and `:accessor` slot options will also be
-  automatically generated.
-
-  Example:
-
-    (define-aspect edible
-      energy
-      (taste :initform nil))
-    =>
-    (defclass edible ()
-      ((edible/energy :initarg :edible/energy
-                      :accessor edible/energy)
-       (edible/taste :initarg :edible/taste
-                     :accessor edible/taste
-                     :initform nil)))
-
-  "
-  (flet ((clean-field (f)
-           (ctypecase f
-             (symbol (list f))
-             (list f))))
-    `(progn
-      (defclass ,name ()
-        ,(loop
-           :for (field . field-options) :in (mapcar #'clean-field fields)
-           :for field-name = (symb name '/ field)
-           :collect `(,field-name
-                      :accessor ,field-name
-                      :initarg ,(ensure-keyword field-name) ; *opens trenchcoat*
-                      ,@field-options)))
-
-      (defun ,(symb name '?) (object)
-        (typep object ',name))
-
-      (initialize-aspect-index ',name)
-
-      (find-class ',name))))
-
-
-;;;; Systems ------------------------------------------------------------------
-(defun rebuild-system-index (arglist)
-  (loop
-    :for (nil . type-specifier) :in arglist
-    :for index = (make-hash-table)
-    :do (loop
-          :for entity :being :the hash-values :of *entity-index*
-          :when (entity-satisfies-system-type-specifier-p entity type-specifier)
-          :do (setf (gethash (entity-id entity) index) entity))
-    :collect index))
-
-(defun initialize-system-index (name function arglist)
-  (setf (gethash name *systems*)
-        (list function (length arglist) (mapcar #'cdr arglist))
-
-        (gethash name *system-index*)
-        (rebuild-system-index arglist)))
-
-
-(defun build-system-runner-1 (name type-specifiers)
-  (with-gensyms (argument-indexes entity)
-    `(let ((,argument-indexes (gethash ',name *system-index*)))
-      (loop :for ,entity :being :the hash-values :of (first ,argument-indexes)
-            :do (locally
-                  (declare (type ,(first type-specifiers) ,entity))
-                  (,name ,entity))))))
-
-(defun build-system-runner-2 (name type-specifiers)
-  (with-gensyms (argument-indexes e1 e2)
-    `(let ((,argument-indexes (gethash ',name *system-index*)))
-      (loop
-        :for ,e1 :being :the hash-values :of (first ,argument-indexes)
-        :do (loop :for ,e2 :being :the hash-values :of (second ,argument-indexes)
-                  :do (locally
-                        (declare (type ,(first type-specifiers) ,e1)
-                                 (type ,(second type-specifiers) ,e2))
-                        (,name ,e1 ,e2)))))))
-
-(defun build-system-runner-n (name)
-  `(apply #'map-product #',name
-    (mapcar #'hash-table-values (gethash ',name *system-index*))))
-
-
-(defun build-system-runner (name arity type-specifiers)
-  (case arity
-    (0 nil)
-    (1 (build-system-runner-1 name type-specifiers))
-    (2 (build-system-runner-2 name type-specifiers))
-    (t (build-system-runner-n name))))
-
-
-(defmacro define-system (name-and-options arglist &body body)
-  "Define a system.
-
-  `name-and-options` should be a list of the system name (a symbol) and any
-  system options.  A bare symbol can be used if no options are needed.
-
-  `arglist` should be a list of system arguments.  Each argument should be
-  a list of the argument name and zero or more aspect/entity classes.
-
-  Defining a system `foo` defines two functions:
-
-  * `foo` runs `body` on a single entity and should only be used for debugging,
-    tracing, or disassembling.
-  * `run-foo` should be called to run the system on all applicable entities.
-
-  Available system options:
-
-  * `:inline`: when true, try to inline the system function into the
-    system-running function to avoid the overhead of a function call for every
-    entity.  Defaults to `nil`.
-
-  Examples:
-
-    (define-system age ((entity lifetime))
-      (when (> (incf (lifetime/age entity))
-               (lifetime/lifespan entity))
-        (destroy-entity entity)))
-
-  "
-  (let ((argument-type-specifiers
-          (loop :for arg :in (mapcar #'ensure-list arglist)
-                :collect `(and entity ,@(cdr arg)))))
-    (destructuring-bind (name &key inline)
-        (ensure-list name-and-options)
-      `(progn
-        (declaim (ftype (function (,@argument-type-specifiers)
-                                  (values null &optional))
-                        ,name)
-                 ,(if inline
-                    `(inline ,name)
-                    `(notinline ,name)))
-        (defun ,name (,@(mapcar #'car arglist))
-          ,@body
-          nil)
-
-        (defun ,(symb 'run- name) ()
-          ,(build-system-runner name (length arglist) argument-type-specifiers))
-
-        (initialize-system-index ',name #',name ',arglist)
-
-        ',name))))
-
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/main.lisp	Sun Aug 29 14:41:27 2021 -0400
@@ -0,0 +1,358 @@
+(in-package :beast)
+
+
+;;;; Notes
+;;; Entities are stored in an {id -> entity} hash table.
+;;;
+;;; Entities are also indexed by aspect in a nested hash table:
+;;;
+;;;     {aspect-symbol -> {id -> entity}}
+;;;
+;;; Entities are indexed by system too, as a vector of hash tables, one entry
+;;; for each of the system's arguments:
+;;;
+;;;     {system-symbol ->
+;;;        #({id -> entity}   ; arg1
+;;;          {id -> entity})  ; arg2
+;;;     }
+;;;
+;;; Systems are stored as:
+;;;
+;;;     {system-symbol -> (system-function arity type-specifier-list)}
+;;;
+;;; TODO: Figure out the distinct problem.
+
+
+;;;; Global Data Structures ---------------------------------------------------
+(defvar *entity-id-counter* 0)
+(defvar *entity-index* (make-hash-table))
+(defvar *aspect-index* (make-hash-table))
+(defvar *system-index* (make-hash-table))
+(defvar *systems* (make-hash-table))
+
+
+;;;; Utils --------------------------------------------------------------------
+(defun symb (&rest args)
+  (values (intern (format nil "~{~A~}" args))))
+
+
+;;;; Entities -----------------------------------------------------------------
+(defclass entity ()
+  ((id
+     :reader entity-id :initform (incf *entity-id-counter*)
+     :documentation
+     "The unique ID of the entity.  This may go away in the future.")
+   (%beast/aspects
+     :allocation :class :initform nil
+     :documentation
+     "A list of the aspects this entity class inherits.  **Don't touch this.**"))
+  (:documentation "A single entity in the game world."))
+
+(defmethod print-object ((e entity) stream)
+  (print-unreadable-object (e stream :type t :identity nil)
+    (format stream "~D" (entity-id e))))
+
+
+(defun entity-satisfies-system-type-specifier-p (entity specifier)
+  (every (lambda (aspect) (typep entity aspect))
+         specifier))
+
+(defun index-entity (entity)
+  "Insert `entity` into the entity index."
+  (setf (gethash (entity-id entity) *entity-index*) entity))
+
+(defun index-entity-aspects (entity)
+  "Insert `entity` into appropriate aspect indexes."
+  (loop :for aspect :in (slot-value entity '%beast/aspects)
+        :do (setf (gethash (entity-id entity)
+                           (gethash aspect *aspect-index*))
+                  entity)))
+
+(defun index-entity-systems (entity)
+  "Insert `entity` into appropriate system indexes."
+  (loop
+    :with id = (entity-id entity)
+    :for system :being :the hash-keys :of *systems*
+    :using (hash-value (nil nil type-specifiers))
+    :do (loop :for argument-index :across (gethash system *system-index*)
+              :for specifier :in type-specifiers
+              :when (entity-satisfies-system-type-specifier-p entity specifier)
+              :do (setf (gethash id argument-index) entity))))
+
+
+(defun unindex-entity (id)
+  "Remove `entity` from the entity-level index."
+  (remhash id *entity-index*))
+
+(defun unindex-entity-aspects (id)
+  "Remove `entity` from the aspect indexes."
+  (loop
+    :for index :being :the :hash-values :of *aspect-index*
+    :do (remhash id index)))
+
+(defun unindex-entity-systems (id)
+  "Remove `entity` from the system indexes."
+  (loop
+    :for argument-indexes :being :the hash-values :of *system-index*
+    :do (loop :for index :across argument-indexes
+              :do (remhash id index))))
+
+
+(defgeneric entity-created (entity)
+  (:method ((entity entity)) nil)
+  (:documentation
+  "Called after an entity has been created and indexed.
+
+  The default method does nothing, but users can implement their own auxillary
+  methods to run code when entities are created.
+
+  "))
+
+(defgeneric entity-destroyed (entity)
+  (:method ((entity entity)) nil)
+  (:documentation
+  "Called after an entity has been destroyed and unindexed.
+
+  The default method does nothing, but users can implement their own auxillary
+  methods to run code when entities are destroyed.
+
+  "))
+
+
+(defun create-entity (class &rest initargs)
+  "Create an entity of the given entity class and return it.
+
+  `initargs` will be passed along to `make-instance`.
+
+  The `entity-created` generic function will be called just before returning the
+  entity.
+
+  "
+  (let ((entity (apply #'make-instance class initargs)))
+    (index-entity entity)
+    (index-entity-aspects entity)
+    (index-entity-systems entity)
+    (entity-created entity)
+    entity))
+
+(defun destroy-entity (entity)
+  "Destroy `entity` and return it.
+
+  The `entity-destroyed` generic function will be called after the entity has
+  been destroyed and unindexed.
+
+  "
+  (let ((id (entity-id entity)))
+    (unindex-entity id)
+    (unindex-entity-aspects id)
+    (unindex-entity-systems id))
+  (entity-destroyed entity)
+  entity)
+
+(defun clear-entities ()
+  "Destroy all entities.
+
+  `destroy-entity` will be called for each entity.
+
+  Returns a list of all the destroyed entites.
+
+  "
+  (let ((entities (all-entities)))
+    (mapc #'destroy-entity entities)
+    entities))
+
+
+(defun get-entity (id)
+  "Return the entity with the given `id`, or `nil` if it is unknown."
+  (gethash id *entity-index*))
+
+(defun all-entities ()
+  "Return a list of all entities.
+
+  Normally you should run code on entities using systems, but this function can
+  be handy for debugging purposes.
+
+  "
+  (loop :for entity :being :the :hash-values :of *entity-index* :collect entity))
+
+(defun map-entities (function &optional (type 'entity))
+  "Map `function` over all entities that are subtypes of `type`.
+
+  Normally you should run code on entities using systems, but this function can
+  be handy for debugging purposes.
+
+  "
+  (loop :for entity :being :the :hash-values :of *entity-index*
+        :when (typep entity type)
+        :collect (funcall function entity)))
+
+
+(defmacro define-entity (name aspects &rest slots)
+  "Define an entity class.
+
+  `name` should be a symbol that will become the name of the class.
+
+  `aspects` should be a list of the aspects this entity should inherit from.
+
+  `slots` can be zero or more extra CLOS slot definitions.
+
+  Examples:
+
+    (define-entity potion (drinkable))
+
+    (define-entity cheese (edible visible)
+      (flavor :accessor cheese-flavor :initarg :flavor))
+
+  "
+  `(progn
+    (defclass ,name (entity ,@aspects)
+      ((%beast/aspects :allocation :class :initform ',aspects)
+       ,@slots))
+    (defun ,(symb name '?) (object)
+      (typep object ',name))
+    (find-class ',name)))
+
+
+;;;; Aspects ------------------------------------------------------------------
+(defun initialize-aspect-index (name)
+  (when (not (gethash name *aspect-index*))
+    (setf (gethash name *aspect-index*) (make-hash-table))))
+
+(defmacro define-aspect (name &rest fields)
+  "Define an aspect class.
+
+  `name` should be a symbol that will become the name of the class.
+
+  `fields` should be zero or more field definitions.  Each field definition can
+  be a symbol (the field name), or a list of the field name and extra CLOS slot
+  options.
+
+  Field names will have the aspect name and a slash prepended to them to create
+  the slot names.  `:initarg` and `:accessor` slot options will also be
+  automatically generated.
+
+  Example:
+
+    (define-aspect edible
+      energy
+      (taste :initform nil))
+    =>
+    (defclass edible ()
+      ((edible/energy :initarg :edible/energy
+                      :accessor edible/energy)
+       (edible/taste :initarg :edible/taste
+                     :accessor edible/taste
+                     :initform nil)))
+
+  "
+  (flet ((clean-field (f)
+           (ctypecase f
+             (symbol (list f))
+             (list f))))
+    `(progn
+      (defclass ,name ()
+        ,(loop
+           :for (field . field-options) :in (mapcar #'clean-field fields)
+           :for field-name = (symb name '/ field)
+           :collect `(,field-name
+                      :accessor ,field-name
+                      :initarg ,(intern (string field-name) :keyword)
+                      ,@field-options)))
+
+      (defun ,(symb name '?) (object)
+        (typep object ',name))
+
+      (initialize-aspect-index ',name)
+
+      (find-class ',name))))
+
+
+;;;; Systems ------------------------------------------------------------------
+(defun rebuild-system-index (arglist)
+  (coerce (loop
+            :for (nil . type-specifier) :in arglist
+            :for index = (make-hash-table)
+            :do (loop
+                  :for entity :being :the :hash-values :of *entity-index*
+                  :when (entity-satisfies-system-type-specifier-p entity type-specifier)
+                  :do (setf (gethash (entity-id entity) index) entity))
+            :collect index)
+          'vector))
+
+(defun initialize-system-index (name function arglist)
+  (setf (gethash name *systems*)
+        (list function (length arglist) (mapcar #'cdr arglist))
+
+        (gethash name *system-index*)
+        (rebuild-system-index arglist)))
+
+
+(defun build-system-runner (name type-specifiers)
+  (unless (null type-specifiers)
+    (let ((argument-indexes (gensym "AI"))
+          (arguments (loop :repeat (length type-specifiers) :collect (gensym "E"))))
+      `(let ((,argument-indexes (gethash ',name *system-index*)))
+         ,(labels ((recur (types args n)
+                     (if (null types)
+                       `(,name ,@arguments)
+                       `(loop
+                          :for ,(first args) :of-type ,(first types)
+                          :being :the :hash-values :of (aref ,argument-indexes ,n)
+                          :do ,(recur (rest types) (rest args) (1+ n))))))
+            (recur type-specifiers arguments 0))))))
+
+
+(defmacro define-system (name-and-options arglist &body body)
+  "Define a system.
+
+  `name-and-options` should be a list of the system name (a symbol) and any
+  system options.  A bare symbol can be used if no options are needed.
+
+  `arglist` should be a list of system arguments.  Each argument should be
+  a list of the argument name and zero or more aspect/entity classes.
+
+  Defining a system `foo` defines two functions:
+
+  * `foo` runs `body` on a single entity and should only be used for debugging,
+    tracing, or disassembling.
+  * `run-foo` should be called to run the system on all applicable entities.
+
+  Available system options:
+
+  * `:inline`: when true, try to inline the system function into the
+    system-running function to avoid the overhead of a function call for every
+    entity.  Defaults to `nil`.
+
+  Examples:
+
+    (define-system age ((entity lifetime))
+      (when (> (incf (lifetime/age entity))
+               (lifetime/lifespan entity))
+        (destroy-entity entity)))
+
+  "
+  (let ((argument-type-specifiers
+          (loop :for arg :in arglist ; either foo or (foo a1 a2)
+                :for classes = (if (listp arg) (rest arg) nil)
+                :collect `(and entity ,@classes))))
+    (destructuring-bind (name &key inline) (if (listp name-and-options)
+                                               name-and-options
+                                               (list name-and-options))
+      `(progn
+        (declaim (ftype (function (,@argument-type-specifiers)
+                                  (values null &optional))
+                        ,name)
+                 ,(if inline
+                    `(inline ,name)
+                    `(notinline ,name)))
+        (defun ,name (,@(mapcar #'car arglist))
+          ,@body
+          nil)
+
+        (defun ,(symb 'run- name) ()
+          ,(build-system-runner name argument-type-specifiers))
+
+        (initialize-system-index ',name #',name ',arglist)
+
+        ',name))))
+
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/package.lisp	Sun Aug 29 14:41:27 2021 -0400
@@ -0,0 +1,20 @@
+(defpackage :beast
+  (:use :cl)
+  (:export
+    :entity
+    :entity-id
+
+    :define-entity
+
+    :create-entity
+    :destroy-entity
+    :clear-entities
+    :map-entities
+    :all-entities
+
+    :entity-created
+    :entity-destroyed
+
+    :define-aspect
+
+    :define-system))
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/package.lisp	Sun Aug 29 14:41:27 2021 -0400
@@ -0,0 +1,3 @@
+(defpackage :beast/test
+  (:use :cl :1am :beast)
+  (:export :run-tests))
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/test/run.lisp	Sun Aug 29 14:41:27 2021 -0400
@@ -0,0 +1,5 @@
+#+ecl (setf compiler:*user-cc-flags* "-Wno-shift-negative-value")
+
+(ql:quickload 'beast :silent t)
+(asdf:test-system 'beast)
+(quit)
--- a/test/test-run.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,3 +0,0 @@
-(ql:quickload 'beast)
-(time (asdf:test-system 'beast))
-(quit)
--- a/test/test.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ b/test/test.lisp	Sun Aug 29 14:41:27 2021 -0400
@@ -1,9 +1,10 @@
-(in-package :beast-test)
+(in-package :beast/test)
 
-;;;; Boilerplate
+;;;; Boilerplate --------------------------------------------------------------
 (defmacro define-test (name &body body)
-  `(test ,name
-    (let ((*package* ,*package*))
+  `(test ,(beast::symb 'test/ name)
+    (let ((*package* ,*package*)
+          (*callbacks* nil))
       (clear-entities)
       ,@body)))
 
@@ -14,11 +15,15 @@
   (null (set-exclusive-or a b :test 'equal)))
 
 
-;;;; Setup
+;;;; Setup --------------------------------------------------------------------
 (defparameter *results* nil)
+(defparameter *callbacks* nil)
 
 (define-aspect a-foo f)
 (define-aspect a-bar b)
+(define-aspect a-baz z)
+(define-aspect a-callbacks-foo)
+(define-aspect a-callbacks-bar)
 
 (define-system sys-everything ((e))
   (push e *results*))
@@ -32,6 +37,9 @@
 (define-system sys-foo-bar ((e a-foo a-bar))
   (push e *results*))
 
+(define-system sys-foo-bar-baz ((e a-foo a-bar a-baz))
+  (push e *results*))
+
 
 (define-system sys2-foo-foo ((x a-foo) (y a-foo))
   (push (list x y) *results*))
@@ -42,20 +50,101 @@
 (define-system sys2-foobar-foo ((x a-foo a-bar) (y a-foo))
   (push (list x y) *results*))
 
+(define-system sys2-foobar-barbaz ((x a-foo a-bar) (y a-bar a-baz))
+  (push (list x y) *results*))
+
+(define-system sys3-foo-bar-baz ((x a-foo) (y a-bar) (z a-baz))
+  (push (list x y z) *results*))
+
 
 (define-entity e ())
 (define-entity e-foo (a-foo))
 (define-entity e-bar (a-bar))
+(define-entity e-baz (a-baz))
 (define-entity e-foo-bar (a-foo a-bar))
+(define-entity e-foo-bar-baz (a-foo a-bar a-baz))
+
+(define-entity e-callbacks-foo (a-callbacks-foo))
+(define-entity e-callbacks-bar (a-callbacks-bar))
+(define-entity e-callbacks-foobarplus (a-callbacks-foo a-callbacks-bar))
+
+(defmethod entity-created :after ((e a-callbacks-foo))        (push (list :created :foo e) *callbacks*))
+(defmethod entity-created :after ((e a-callbacks-bar))        (push (list :created :bar e) *callbacks*))
+(defmethod entity-created :after ((e e-callbacks-foobarplus)) (push (list :created :ent e) *callbacks*))
+
+(defmethod entity-destroyed :after ((e a-callbacks-foo))        (push (list :destroyed :foo e) *callbacks*))
+(defmethod entity-destroyed :after ((e a-callbacks-bar))        (push (list :destroyed :bar e) *callbacks*))
+(defmethod entity-destroyed :after ((e e-callbacks-foobarplus)) (push (list :destroyed :ent e) *callbacks*))
 
 
-;;;; Tests
+;;;; Tests --------------------------------------------------------------------
 (define-test create-entities
   (let ((a (create-entity 'e))
         (b (create-entity 'e)))
-    (is (set-equal (list a b) (beast::all-entities)))
+    (is (set-equal (list a b) (beast:all-entities)))
+    (let ((c (create-entity 'e)))
+      (is (set-equal (list a b c) (beast:all-entities))))))
+
+(define-test destroy-entities
+  (let ((a (create-entity 'e))
+        (b (create-entity 'e)))
+    (is (set-equal (list a b) (beast:all-entities)))
+    (destroy-entity a)
+    (is (set-equal (list b) (beast:all-entities)))
     (let ((c (create-entity 'e)))
-      (is (set-equal (list a b c) (beast::all-entities))))))
+      (is (set-equal (list b c) (beast:all-entities)))
+      (destroy-entity b)
+      (is (set-equal (list c) (beast:all-entities)))
+      (destroy-entity c)
+      (is (set-equal (list) (beast:all-entities))))))
+
+(define-test clear-entities
+  (let ((a (create-entity 'e))
+        (b (create-entity 'e)))
+    (is (set-equal (list a b) (beast:all-entities)))
+    (clear-entities)
+    (is (set-equal (list) (beast:all-entities)))))
+
+(define-test callbacks
+  (let (*callbacks* f b fbp)
+    (is (set-equal `() *callbacks*))
+
+    (setf f (create-entity 'e-callbacks-foo))
+    (is (set-equal `((:created :foo ,f)) *callbacks*))
+    (setf *callbacks* nil)
+
+    (setf b (create-entity 'e-callbacks-bar))
+    (is (set-equal `((:created :bar ,b)) *callbacks*))
+    (setf *callbacks* nil)
+
+    (setf fbp (create-entity 'e-callbacks-foobarplus))
+    (is (set-equal `((:created :bar ,fbp)
+                     (:created :foo ,fbp)
+                     (:created :ent ,fbp)) *callbacks*))
+    (setf *callbacks* nil)
+
+    (destroy-entity fbp)
+    (is (set-equal `((:destroyed :bar ,fbp)
+                     (:destroyed :foo ,fbp)
+                     (:destroyed :ent ,fbp)) *callbacks*))
+    (setf *callbacks* nil)
+
+    (destroy-entity f)
+    (is (set-equal `((:destroyed :foo ,f)) *callbacks*))
+    (setf *callbacks* nil)
+
+    (destroy-entity b)
+    (is (set-equal `((:destroyed :bar ,b)) *callbacks*))))
+
+(define-test map-entities
+  (create-entity 'e-foo :a-foo/f 1)
+  (create-entity 'e-foo :a-foo/f 2)
+  (is (set-equal (list 1 2) (beast:map-entities #'a-foo/f)))
+  (create-entity 'e-foo :a-foo/f 3)
+  (is (set-equal (list 1 2 3) (beast:map-entities #'a-foo/f)))
+  (create-entity 'e-bar :a-bar/b 0)
+  (is (set-equal (list 1 2 3) (beast:map-entities #'a-foo/f 'a-foo)))
+  (is (set-equal (list 0) (beast:map-entities #'a-bar/b 'a-bar))))
 
 (define-test get-entities
   (let ((a (create-entity 'e))
@@ -118,3 +207,33 @@
       (run-sys2-foobar-foo)
       (is (set-equal *results* (list (list fb f)
                                      (list fb fb)))))))
+
+(define-test system-running-arity-3
+  (let ((f (create-entity 'e-foo))
+        (b (create-entity 'e-bar))
+        (z (create-entity 'e-baz))
+        (fb (create-entity 'e-foo-bar))
+        (fbz (create-entity 'e-foo-bar-baz)))
+    (let ((*results* nil))
+      (run-sys3-foo-bar-baz)
+      (is (set-equal *results* (list
+                                 (list f     b     z)
+                                 (list f     b   fbz)
+                                 (list f    fb     z)
+                                 (list f    fb   fbz)
+                                 (list f    fbz    z)
+                                 (list f    fbz  fbz)
+
+                                 (list fb    b     z)
+                                 (list fb    b   fbz)
+                                 (list fb   fb     z)
+                                 (list fb   fb   fbz)
+                                 (list fb   fbz    z)
+                                 (list fb   fbz  fbz)
+
+                                 (list fbz   b     z)
+                                 (list fbz   b   fbz)
+                                 (list fbz  fb     z)
+                                 (list fbz  fb   fbz)
+                                 (list fbz  fbz    z)
+                                 (list fbz  fbz  fbz)))))))
--- a/vendor/make-quickutils.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,12 +0,0 @@
-(ql:quickload 'quickutil)
-
-(qtlc:save-utils-as
-  "quickutils.lisp"
-  :utilities '(:map-product
-               :hash-table-key-exists-p
-               :hash-table-values
-               :with-gensyms
-               :symb
-               :ensure-keyword
-               :ensure-list)
-  :package "BEAST.QUICKUTILS")
--- a/vendor/quickutils-package.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,12 +0,0 @@
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  (unless (find-package "BEAST.QUICKUTILS")
-    (defpackage "BEAST.QUICKUTILS"
-      (:documentation "Package that contains Quickutil utility functions.")
-      (:use #:cl))))
-
-(in-package "BEAST.QUICKUTILS")
-
-;; need to define this here so sbcl will shut the hell up about it being
-;; undefined when compiling quickutils.lisp.  computers are trash.
-(defparameter *utilities* nil)
-
--- a/vendor/quickutils.lisp	Tue Jan 14 19:51:18 2020 -0500
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,194 +0,0 @@
-;;;; This file was automatically generated by Quickutil.
-;;;; See http://quickutil.org for details.
-
-;;;; To regenerate:
-;;;; (qtlc:save-utils-as "quickutils.lisp" :utilities '(:MAP-PRODUCT :HASH-TABLE-KEY-EXISTS-P :HASH-TABLE-VALUES :WITH-GENSYMS :SYMB :ENSURE-KEYWORD :ENSURE-LIST) :ensure-package T :package "BEAST.QUICKUTILS")
-
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  (unless (find-package "BEAST.QUICKUTILS")
-    (defpackage "BEAST.QUICKUTILS"
-      (:documentation "Package that contains Quickutil utility functions.")
-      (:use #:cl))))
-
-(in-package "BEAST.QUICKUTILS")
-
-(when (boundp '*utilities*)
-  (setf *utilities* (union *utilities* '(:MAKE-GENSYM-LIST :ENSURE-FUNCTION
-                                         :CURRY :MAPPEND :MAP-PRODUCT
-                                         :HASH-TABLE-KEY-EXISTS-P
-                                         :MAPHASH-VALUES :HASH-TABLE-VALUES
-                                         :STRING-DESIGNATOR :WITH-GENSYMS
-                                         :MKSTR :SYMB :ENSURE-KEYWORD
-                                         :ENSURE-LIST))))
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  (defun make-gensym-list (length &optional (x "G"))
-    "Returns a list of `length` gensyms, each generated as if with a call to `make-gensym`,
-using the second (optional, defaulting to `\"G\"`) argument."
-    (let ((g (if (typep x '(integer 0)) x (string x))))
-      (loop repeat length
-            collect (gensym g))))
-  )                                        ; eval-when
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  ;;; To propagate return type and allow the compiler to eliminate the IF when
-  ;;; it is known if the argument is function or not.
-  (declaim (inline ensure-function))
-
-  (declaim (ftype (function (t) (values function &optional))
-                  ensure-function))
-  (defun ensure-function (function-designator)
-    "Returns the function designated by `function-designator`:
-if `function-designator` is a function, it is returned, otherwise
-it must be a function name and its `fdefinition` is returned."
-    (if (functionp function-designator)
-        function-designator
-        (fdefinition function-designator)))
-  )                                        ; eval-when
-
-  (defun curry (function &rest arguments)
-    "Returns a function that applies `arguments` and the arguments
-it is called with to `function`."
-    (declare (optimize (speed 3) (safety 1) (debug 1)))
-    (let ((fn (ensure-function function)))
-      (lambda (&rest more)
-        (declare (dynamic-extent more))
-        ;; Using M-V-C we don't need to append the arguments.
-        (multiple-value-call fn (values-list arguments) (values-list more)))))
-
-  (define-compiler-macro curry (function &rest arguments)
-    (let ((curries (make-gensym-list (length arguments) "CURRY"))
-          (fun (gensym "FUN")))
-      `(let ((,fun (ensure-function ,function))
-             ,@(mapcar #'list curries arguments))
-         (declare (optimize (speed 3) (safety 1) (debug 1)))
-         (lambda (&rest more)
-           (apply ,fun ,@curries more)))))
-  
-
-  (defun mappend (function &rest lists)
-    "Applies `function` to respective element(s) of each `list`, appending all the
-all the result list to a single list. `function` must return a list."
-    (loop for results in (apply #'mapcar function lists)
-          append results))
-  
-
-  (defun map-product (function list &rest more-lists)
-    "Returns a list containing the results of calling `function` with one argument
-from `list`, and one from each of `more-lists` for each combination of arguments.
-In other words, returns the product of `list` and `more-lists` using `function`.
-
-Example:
-
-    (map-product 'list '(1 2) '(3 4) '(5 6))
-     => ((1 3 5) (1 3 6) (1 4 5) (1 4 6)
-         (2 3 5) (2 3 6) (2 4 5) (2 4 6))"
-    (labels ((%map-product (f lists)
-               (let ((more (cdr lists))
-                     (one (car lists)))
-                 (if (not more)
-                     (mapcar f one)
-                     (mappend (lambda (x)
-                                (%map-product (curry f x) more))
-                              one)))))
-      (%map-product (ensure-function function) (cons list more-lists))))
-  
-
-  (defun hash-table-key-exists-p (hash-table key)
-    "Does `key` exist in `hash-table`?"
-    (nth-value 1 (gethash key hash-table)))
-  
-
-  (declaim (inline maphash-values))
-  (defun maphash-values (function table)
-    "Like `maphash`, but calls `function` with each value in the hash table `table`."
-    (maphash (lambda (k v)
-               (declare (ignore k))
-               (funcall function v))
-             table))
-  
-
-  (defun hash-table-values (table)
-    "Returns a list containing the values of hash table `table`."
-    (let ((values nil))
-      (maphash-values (lambda (v)
-                        (push v values))
-                      table)
-      values))
-  
-
-  (deftype string-designator ()
-    "A string designator type. A string designator is either a string, a symbol,
-or a character."
-    `(or symbol string character))
-  
-
-  (defmacro with-gensyms (names &body forms)
-    "Binds each variable named by a symbol in `names` to a unique symbol around
-`forms`. Each of `names` must either be either a symbol, or of the form:
-
-    (symbol string-designator)
-
-Bare symbols appearing in `names` are equivalent to:
-
-    (symbol symbol)
-
-The string-designator is used as the argument to `gensym` when constructing the
-unique symbol the named variable will be bound to."
-    `(let ,(mapcar (lambda (name)
-                     (multiple-value-bind (symbol string)
-                         (etypecase name
-                           (symbol
-                            (values name (symbol-name name)))
-                           ((cons symbol (cons string-designator null))
-                            (values (first name) (string (second name)))))
-                       `(,symbol (gensym ,string))))
-            names)
-       ,@forms))
-
-  (defmacro with-unique-names (names &body forms)
-    "Binds each variable named by a symbol in `names` to a unique symbol around
-`forms`. Each of `names` must either be either a symbol, or of the form:
-
-    (symbol string-designator)
-
-Bare symbols appearing in `names` are equivalent to:
-
-    (symbol symbol)
-
-The string-designator is used as the argument to `gensym` when constructing the
-unique symbol the named variable will be bound to."
-    `(with-gensyms ,names ,@forms))
-  
-
-  (defun mkstr (&rest args)
-    "Receives any number of objects (string, symbol, keyword, char, number), extracts all printed representations, and concatenates them all into one string.
-
-Extracted from _On Lisp_, chapter 4."
-    (with-output-to-string (s)
-      (dolist (a args) (princ a s))))
-  
-
-  (defun symb (&rest args)
-    "Receives any number of objects, concatenates all into one string with `#'mkstr` and converts them to symbol.
-
-Extracted from _On Lisp_, chapter 4.
-
-See also: `symbolicate`"
-    (values (intern (apply #'mkstr args))))
-  
-
-  (defun ensure-keyword (x)
-    "Ensure that a keyword is returned for the string designator `x`."
-    (values (intern (string x) :keyword)))
-  
-
-  (defun ensure-list (list)
-    "If `list` is a list, it is returned. Otherwise returns the list designated by `list`."
-    (if (listp list)
-        list
-        (list list)))
-  
-(eval-when (:compile-toplevel :load-toplevel :execute)
-  (export '(map-product hash-table-key-exists-p hash-table-values with-gensyms
-            with-unique-names symb ensure-keyword ensure-list)))
-
-;;;; END OF quickutils.lisp ;;;;