diff --git a/minimart/ground.rkt b/minimart/ground.rkt
index 54bc532..a547786 100644
--- a/minimart/ground.rkt
+++ b/minimart/ground.rkt
@@ -1,4 +1,5 @@
 #lang racket/base
+;; Breaking the infinite tower of nested Worlds, connecting to the "real" world at the fracture line.
 
 (require racket/async-channel)
 (require racket/set)
@@ -11,20 +12,36 @@
 	 send-ground-message
 	 run-ground)
 
+;; A GroundEvent is a pair of a Racket (evt?) event and its yielded
+;; results.
+;;  - (event RacketEvent (Listof Any))
 (struct event (descriptor values) #:prefab)
 
+;; (Parameterof (Option AsyncChannel))
+;; Communication channel from auxiliary (usually driver) threads to
+;; the currently-active ground VM.
 (define current-ground-event-async-channel (make-parameter #f))
 
+;; Any -> Void
+;; Sends a (non-feedback) message at the ground-VM metalevel.
 (define (send-ground-message body)
   (match (current-ground-event-async-channel)
     [(? async-channel? ch) (async-channel-put ch (send body))]
     [_ (error 'send-ground-message "Called outside dynamic scope of run-ground")]))
 
+;; RacketEvent -> RacketEvent
+;; Wraps a CML-style Racket event with a handler that sends the event
+;; results via the ground VM.
 (define (event-handler descriptor)
   (handle-evt descriptor (lambda vs (send (event descriptor vs)))))
 
+;; CompiledProjection
+;; Used to extract event descriptors and results from subscriptions
+;; from the ground VM's contained World.
 (define event-projection (compile-gestalt-projection (event (?!) ?)))
 
+;; Gestalt -> (Listof RacketEvent)
+;; Projects out the active event subscriptions from the given gestalt.
 (define (extract-active-events gestalt)
   (define es (matcher-key-set (gestalt-project gestalt 0 0 #f event-projection)))
   ;; TODO: how should the following error be handled, ideally?
@@ -36,9 +53,14 @@
     (match-define (list e) ev)
     (event-handler e)))
 
+;; RacketEvent
+;; Used only when the system is not provably inert, in order to let it
+;; take further internal reductions.
 (define idle-handler
   (handle-evt (system-idle-evt) (lambda _ #f)))
 
+;; Action* -> Void
+;; Runs a ground VM, booting the outermost World with the given Actions.
 (define (run-ground . boot-actions)
   (parameterize ((current-ground-event-async-channel (make-async-channel)))
     (let await-interrupt ((inert? #f) (p (spawn-world boot-actions)) (active-events '()))