It always help me to visualize things early in the development process. Let's see what we have so far:
(require srfi/43)
(define terrain-width 12)
(define terrain-height 12)
(define (print-terrain)
(vector-for-each (lambda (i n)
(cond ((zero? (remainder (+ i 1) terrain-width)) (newline))
((eq? n 'floor) (display ".")))) terrain))
(print-terrain)
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...........Nice.