diff --git a/core.rkt b/core.rkt
new file mode 100644
index 0000000..cef2671
--- /dev/null
+++ b/core.rkt
@@ -0,0 +1,211 @@
+#lang racket/base
+
+(require racket/match)
+(require racket/list)
+(require "pattern.rkt")
+(require "functional-queue.rkt")
+(require (only-in web-server/private/util exn->string))
+
+(provide (struct-out route)
+	 (struct-out routing-update)
+	 (struct-out message)
+	 (struct-out quit)
+	 (struct-out process)
+	 (struct-out transition)
+	 sub
+	 pub
+	 spawn
+	 send
+	 feedback
+	 spawn-world
+	 transition-bind
+	 sequence-transitions)
+
+(struct route (subscription? pattern meta-level level) #:prefab)
+
+;; Events
+(struct routing-update (routes) #:prefab)
+(struct message (body meta-level feedback?) #:prefab)
+
+;; Actions (in addition to Events)
+;; (spawn is just process)
+(struct quit () #:prefab)
+
+;; Actors and Configurations
+(struct process (routes behavior state) #:transparent)
+(struct world (next-pid event-queue process-table downward-routes process-actions) #:transparent)
+
+;; Behavior : maybe event * state -> transition
+(struct transition (state actions) #:transparent)
+
+(define (drop-route r)
+  (match-define (route s? p ml l) r)
+  (and (positive? ml) (route s? p (- ml 1) l)))
+
+(define (lift-route r)
+  (match-define (route s? p ml l) r)
+  (route s? p (+ ml 1) l))
+
+(define (sub p #:meta-level [ml 0] #:level [l 0]) (route #t p ml l))
+(define (pub p #:meta-level [ml 0] #:level [l 0]) (route #t p ml l))
+
+(define (spawn behavior state [initial-routes '()]) (process initial-routes behavior state))
+(define (send body #:meta-level [ml 0]) (message body ml #f))
+(define (feedback body #:meta-level [ml 0]) (message body ml #t))
+
+(define (drop-routes rs) (filter-map drop-route rs))
+(define (lift-routes rs) (map lift-routes rs))
+
+(define (intersect-routes rs1 rs2)
+  (let loop1 ((rs1 rs1)
+	      (acc '()))
+    (match rs1
+      ['() (reverse acc)]
+      [(cons r1 rs1)
+       (let loop2 ((rs2 rs2)
+		   (acc acc))
+	 (match rs2
+	   ['() (loop1 rs1 acc)]
+	   [(cons r2 rs2)
+	    (if (and (equal? (route-subscription? r1) (not (route-subscription? r2)))
+		     (= (route-meta-level r1) (route-meta-level r2))
+		     (< (route-level r1) (route-level r2)))
+		(intersect (route-pattern r1) (route-pattern r2)
+			   (lambda (rr) (loop2 rs2 (cons rr acc)))
+			   (lambda () (loop2 rs2 acc)))
+		(loop2 rs2 acc))]))])))
+
+(define (filter-event e rs)
+  (match e
+    [(routing-update e-rs)
+     (routing-update (intersect-routes e-rs rs))]
+    [(message body meta-level feedback?)
+     (let loop ((rs rs))
+       (match rs
+	 ['() #f]
+	 [(cons r rs)
+	  (and (= meta-level (route-meta-level r))
+	       (equal? feedback? (not (route-subscription? r)))
+	       (intersect body (route-pattern r)
+			  (lambda (dummy) e)
+			  (lambda () (loop rs))))]))]))
+
+(define (spawn-world boot-actions)
+  (spawn world-handle-event
+	 (enqueue-actions (world 0
+				 (make-queue)
+				 (hash)
+				 '()
+				 (make-queue))
+			  -1
+			  boot-actions)))
+
+(define (enqueue-actions w pid actions)
+  (struct-copy world w
+    [process-actions (queue-append-list (world-process-actions w)
+					(map (lambda (a) (cons pid a)) (flatten actions)))]))
+
+(define (quiescent? w)
+  (and (queue-empty? (world-event-queue w))
+       (queue-empty? (world-process-actions w))))
+
+(define (deliver e pid p)
+  (with-handlers ([(lambda (exn) #t)
+		   (lambda (exn)
+		     (log-error "Process ~a died with exception:\n~a" pid (exn->string exn))
+		     (transition (process-state p) (list (quit))))])
+    ((process-behavior p) e (process-state p))))
+
+(define (apply-transition pid t w)
+  (match-define (transition new-state new-actions) t)
+  (let* ((w (transform-process pid w (lambda (p) (struct-copy process p [state new-state])))))
+    (enqueue-actions w pid new-actions)))
+
+(define (step-children w)
+  (let-values (((w step-taken?)
+		(for/fold ([w w] [step-taken? #f]) (((pid p) (in-hash (world-process-table w))))
+		  (define t (deliver #f pid p))
+		  (if t
+		      (values (apply-transition pid t w) #t)
+		      (values w step-taken?)))))
+    (and step-taken? (transition w '()))))
+
+(define (transition-bind k t0)
+  (match-define (transition state0 actions0) t0)
+  (match-define (transition state1 actions1) (k state0))
+  (transition state1 (cons actions0 actions1)))
+
+(define (sequence-transitions t0 . steps)
+  (foldl transition-bind t0 steps))
+
+(define (perform-actions w)
+  (for/fold ([t (transition (struct-copy world w [process-actions (make-queue)]) '())])
+      ((entry (in-list (queue->list (world-process-actions w)))))
+    (match-define (cons pid a) entry)
+    (transition-bind (perform-action pid a) t)))
+
+(define (dispatch-events w)
+  (transition (for/fold ([w (struct-copy world w [event-queue (make-queue)])])
+		  ((e (in-list (queue->list (world-event-queue w)))))
+		(dispatch-event e w))
+              '()))
+
+(define (transform-process pid w f)
+  (define p (hash-ref (world-process-table w) pid))
+  (if p
+      (struct-copy world w [process-table (hash-set (world-process-table w) pid (f p))])
+      w))
+
+(define (enqueue-event e w)
+  (struct-copy world w [event-queue (enqueue (world-event-queue w) e)]))
+
+(define ((perform-action pid a) w)
+  (match a
+    [(? process? new-p)
+     (let* ((new-pid (world-next-pid w))
+	    (w (struct-copy world w [next-pid (+ new-pid 1)]))
+	    (w (struct-copy world w [process-table
+				     (hash-set (world-process-table w) new-pid new-p)])))
+       (issue-routing-update w))]
+    [(quit)
+     (let* ((w (struct-copy world w [process-table (hash-remove (world-process-table w) pid)])))
+       (issue-routing-update w))]
+    [(routing-update routes)
+     (let* ((w (transform-process pid w (lambda (p) (struct-copy process p [routes routes])))))
+       (issue-routing-update w))]
+    [(message body meta-level feedback?)
+     (if (zero? meta-level)
+	 (transition (enqueue-event a w) '())
+	 (transition w (message body (- meta-level 1) feedback?)))]))
+
+(define (aggregate-routes base w)
+  (apply append base (for/list ((p (in-hash-values (world-process-table w)))) (process-routes p))))
+
+(define (issue-local-routing-update w)
+  (enqueue-event (routing-update (aggregate-routes (world-downward-routes w) w)) w))
+
+(define (issue-routing-update w)
+  (transition (issue-local-routing-update w)
+              (routing-update (drop-routes (aggregate-routes '() w)))))
+
+(define (dispatch-event e w)
+  (for/fold ([w w]) (((pid p) (in-hash (world-process-table w))))
+    (define e1 (filter-event e (process-routes p)))
+    (if e1
+	(apply-transition pid (deliver e1 pid p) w)
+	w)))
+
+(define (world-handle-event e w)
+  (if (or e (not (quiescent? w)))
+      (sequence-transitions (transition (inject-event e w) '())
+			    dispatch-events
+			    perform-actions
+			    (lambda (w) (or (step-children w) (transition w '()))))
+      (step-children w)))
+
+(define (inject-event e w)
+  (match e
+    [(routing-update routes)
+     (issue-local-routing-update (struct-copy world w [downward-routes (lift-routes routes)]))]
+    [(message body meta-level feedback?)
+     (enqueue-event (message body (+ meta-level 1) feedback?) w)]))