Wordle in 20 lines of bash

wordle.bash

#!/usr/bin/env bash
mapfile -t words < <(grep -x '[a-z]\{5\}' "${WORDLIST:-/usr/share/dict/words}")
word=${words[RANDOM % ${#words[@]}]} pool=abcdefghijklmnopqrstuvwxyz
for ((round=1; round <= ${ROUNDS:=6}; round++)); do
	while read -rp "$round/$ROUNDS: " guess || exit 1; do
		[[ " ${words[@]} " == *" ${guess,,} "* ]] && guess=${guess,,} && break
	done
	for ((i=0, chars=0; i < ${#word}; i++)); do
		[[ ${word:i:1} != ${guess:i:1} ]] && chars+=${word:i:1}
	done
	for ((i=0; color=7, i < ${#guess}; i++)); do char=${guess:i:1}
		{ [[ ${word:i:1} == $char ]] && color=2; } ||
		{ [[ ${chars#0} == *$char* ]] && color=3 chars=${chars/$char/}; }
		[[ $word != *$char* ]] && pool=${pool/$char/}
		printf '\033[30;4%dm %s \033[0m' "$color" "${char^^}"
	done
	printf ' %s\n' "$pool"
	[[ $guess == $word ]] && exit
done
! printf 'The word was "%s"\n' "$word" && false

@jcromero - Because I didn't quite grok what was going on and wanted to disturb as little a possible.

@aaronNGi - sweet. Thank you for considering my edits.