Refactor(English): Rename all files and identifiers from Dutch to English

Renamed files: constanten→constants, adt-positie→adt-position,
adt-doolhof→adt-maze, adt-sleutel→adt-key, adt-tijdslimiet→adt-timer,
adt-teken→adt-draw, adt-spel→adt-game. All message names, variables,
comments, and tests converted to English.

Also fixed counter location bug (time-label x/y were swapped).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pacman-project/adt-timer.rkt

@@ -0,0 +1,62 @@
+#lang r7rs
+
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;                                Timer ADT                                  ;;
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Manages the countdown time limit. Contains NO graphics code.
+
+(define-library (pacman-project adt-timer)
+  (import (scheme base)
+          (pacman-project constants))
+  (export make-timer)
+
+  (begin
+
+    ;; make-timer :: -> timer
+    ;; Creates a new timer object.
+    (define (make-timer)
+      (let ((remaining-time start-time-seconds)
+            (time-since-last-tick 0))
+
+        ;; decrease! :: number -> /
+        ;; Decreases time based on elapsed milliseconds.
+        (define (decrease! ms)
+          (set! time-since-last-tick (+ time-since-last-tick ms))
+          (when (>= time-since-last-tick ms-per-second)
+            (set! time-since-last-tick 0)
+            (when (> remaining-time 0)
+              (set! remaining-time (- remaining-time 1)))))
+
+        ;; increase! :: -> /
+        ;; Adds a time bonus (when eating a coin).
+        (define (increase!)
+          (set! remaining-time (+ remaining-time time-bonus-per-coin)))
+
+        ;; time-up? :: -> boolean
+        (define (time-up?)
+          (= remaining-time 0))
+
+        ;; format-time :: -> string
+        ;; Returns remaining time as "m:ss" string.
+        (define (format-time)
+          (let* ((minutes (quotient remaining-time 60))
+                 (seconds (remainder remaining-time 60))
+                 (min-str (number->string minutes))
+                 (sec-str (number->string seconds)))
+            (string-append min-str
+                           ":"
+                           (if (< seconds 10)
+                               (string-append "0" sec-str)
+                               sec-str))))
+
+        ;; dispatch-timer :: symbol -> any
+        (define (dispatch-timer msg)
+          (cond ((eq? msg 'remaining-time) remaining-time)
+                ((eq? msg 'decrease!) decrease!)
+                ((eq? msg 'increase!) increase!)
+                ((eq? msg 'time-up?) time-up?)
+                ((eq? msg 'format-time) format-time)
+                (else (error "Timer ADT -- Unknown message:" msg))))
+
+        dispatch-timer))))