diff --git a/.continue/rules/project.md b/.continue/rules/project.md
index 310d482..bdb539a 100644
--- a/.continue/rules/project.md
+++ b/.continue/rules/project.md
@@ -22,6 +22,8 @@ description: mtm-ddwipe project conventions
 - Do not make new external tools required.
 - Keep changes minimal and preserve intent.
 - Keep this file aligned and concise.
+- Prefer tabs for indentation.
+- Prefer `${var}` notation in Bash.
 - If non-interactive support is added, make it an opt-in safety flag.
 
 # Project identity
diff --git a/README.md b/README.md
index 5847a34..ebc19f8 100644
--- a/README.md
+++ b/README.md
@@ -2,13 +2,18 @@
 
 Wipe a block device.
 
-Warning: destructive and irreversible. The target must be a real block device, not mounted, and not in use.
+Warning: destructive and irreversible.
+Target must be a real block device, not mounted, and not in use.
 
 Usage:
-mtm-ddwipe DEVICE
+	mtm-ddwipe DEVICE
+	mtm-ddwipe -h | --help
 
 Options:
-- `-h`, `--help`
+	-h, --help	Show help.
 
-Optional tools: `blkdiscard`, `ddrescue`, `dd_rescue`, `nvme`, `hdparm`.
+Notes:
+	- Interactive by default.
+	- Confirm exactly before wiping.
+	- Optional tools: blkdiscard, ddrescue, dd_rescue, nvme, hdparm.
 
diff --git a/mtm-ddwipe b/mtm-ddwipe
index e61511b..9818e8b 100644
--- a/mtm-ddwipe
+++ b/mtm-ddwipe
@@ -33,70 +33,74 @@ die() {
 
 check_args() {
 	if [ $# -ne 1 ]; then
+		case "${1:-}" in
+			-h|--help)
+				usage
+				exit 0
+				;;
+			"")
+				usage
+				exit 1
+				;;
+			-*)
+				die "Invalid option."
+				;;
+		esac
+
 		usage
 		exit 1
 	fi
-
-	case "$1" in
-		-h|--help)
-			usage
-			exit 0
-			;;
-		-*)
-			die "Invalid option."
-			;;
-	esac
 }
 
 check_device() {
-	local dev="$1"
+	local dev="${1}"
 
-	[ -e "$dev" ] || die "Missing device: $dev"
-	[ -b "$dev" ] || die "Not a block device: $dev"
+	[ -e "${dev}" ] || die "Missing device: ${dev}"
+	[ -b "${dev}" ] || die "Not a block device: ${dev}"
 }
 
 check_device_not_in_use() {
-	local dev="$1"
+	local dev="${1}"
 
-	if findmnt -rn --target "$dev" >/dev/null 2>&1; then
-		die "Device is mounted: $dev"
+	if findmnt -rn --target "${dev}" >/dev/null 2>&1; then
+		die "Device is mounted: ${dev}"
 	fi
 
-	if lsblk -nrpo NAME,MOUNTPOINT "$dev" | awk '$2 != "" { found=1 } END { exit !found }'; then
-		die "Device or child is mounted: $dev"
+	if lsblk -nrpo NAME,MOUNTPOINT "${dev}" | awk '$2 != "" { found=1 } END { exit !found }'; then
+		die "Device or child is mounted: ${dev}"
 	fi
 }
 
 is_nvme_device() {
-	local dev="$1"
+	local dev="${1}"
 	local sysdev
 
-	sysdev="/sys$(lsblk -ndo PATH "$dev" 2>/dev/null | head -n1)"
-	[ -n "$sysdev" ] || return 1
-	[ -e "$sysdev" ] || return 1
-	[ -d "$sysdev/device" ] || return 1
-	[ -e "$sysdev/device/uevent" ] || return 1
-	grep -q '^NVME=1$' "$sysdev/device/uevent"
+	sysdev="/sys$(lsblk -ndo PATH "${dev}" 2>/dev/null | head -n1)"
+	[ -n "${sysdev}" ] || return 1
+	[ -e "${sysdev}" ] || return 1
+	[ -d "${sysdev}/device" ] || return 1
+	[ -e "${sysdev}/device/uevent" ] || return 1
+	grep -q '^NVME=1$' "${sysdev}/device/uevent"
 }
 
 is_ata_device() {
-	local dev="$1"
+	local dev="${1}"
 	local tran
 
-	tran="$(lsblk -ndo TRAN "$dev" 2>/dev/null | head -n1)"
-	[ "$tran" = "sata" ] || [ "$tran" = "ata" ]
+	tran="$(lsblk -ndo TRAN "${dev}" 2>/dev/null | head -n1)"
+	[ "${tran}" = "sata" ] || [ "${tran}" = "ata" ]
 }
 
 confirm_wipe() {
-	local dev="$1"
+	local dev="${1}"
 	local choice=""
 
 	echo "Device:"
-	lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINT,MODEL,SERIAL "$dev"
+	lsblk -o NAME,SIZE,TYPE,FSTYPE,MOUNTPOINT,MODEL,SERIAL "${dev}"
 	echo ""
-	echo "Type exactly: WIPE $dev"
+	echo "Type exactly: WIPE ${dev}"
 	read -r -p "Confirm: " choice
-	[ "$choice" = "WIPE $dev" ] || die "Canceled"
+	[ "${choice}" = "WIPE ${dev}" ] || die "Canceled"
 	echo ""
 }
 
@@ -107,14 +111,14 @@ confirm_root() {
 }
 
 format_duration() {
-	local total="$1"
+	local total="${1}"
 	local hours minutes seconds
 
 	hours=$((total / 3600))
 	minutes=$(((total % 3600) / 60))
 	seconds=$((total % 60))
 
-	printf '%02d:%02d:%02d\n' "$hours" "$minutes" "$seconds"
+	printf '%02d:%02d:%02d\n' "${hours}" "${minutes}" "${seconds}"
 }
 
 print_time() {
@@ -122,7 +126,7 @@ print_time() {
 
 	echo ""
 	log "Start date :"
-	log "$STARTDATESTRING"
+	log "${STARTDATESTRING}"
 
 	enddate=$(date +%s)
 	calctime=$((enddate - STARTDATE))
@@ -133,121 +137,121 @@ print_time() {
 
 	echo ""
 	log "Total time :"
-	format_duration "$calctime" >&2
+	format_duration "${calctime}" >&2
 }
 
 wipe_with_blkdiscard_secure() {
-	local dev="$1"
+	local dev="${1}"
 
 	log "blkdiscard secure"
-	blkdiscard -f -p 500M -s -v "$dev"
+	blkdiscard -f -p 500M -s -v "${dev}"
 }
 
 wipe_with_blkdiscard_zero() {
-	local dev="$1"
+	local dev="${1}"
 
 	log "blkdiscard zero"
-	blkdiscard -f -p 500M -z -v "$dev"
+	blkdiscard -f -p 500M -z -v "${dev}"
 }
 
 wipe_with_dd() {
-	local dev="$1"
+	local dev="${1}"
 
 	log "dd zero"
-	dd if=/dev/zero of="$dev" bs=1M status=progress conv=fsync
+	dd if=/dev/zero of="${dev}" bs=1M status=progress conv=fsync
 }
 
 wipe_with_ddrescue() {
-	local dev="$1"
+	local dev="${1}"
 
 	command -v ddrescue >/dev/null 2>&1 || return 1
 	log "ddrescue zero"
-	ddrescue -f -n /dev/zero "$dev"
+	ddrescue -f -n /dev/zero "${dev}"
 }
 
 wipe_with_dd_rescue() {
-	local dev="$1"
+	local dev="${1}"
 
 	command -v dd_rescue >/dev/null 2>&1 || return 1
 	log "dd_rescue zero"
-	dd_rescue -f /dev/zero "$dev"
+	dd_rescue -f /dev/zero "${dev}"
 }
 
 wipe_with_nvme() {
-	local dev="$1"
+	local dev="${1}"
 
 	command -v nvme >/dev/null 2>&1 || return 1
-	is_nvme_device "$dev" || return 1
+	is_nvme_device "${dev}" || return 1
 	log "nvme format"
-	nvme format "$dev" -s 1 >/dev/null
+	nvme format "${dev}" -s 1 >/dev/null
 }
 
 wipe_with_hdparm() {
-	local dev="$1"
+	local dev="${1}"
 
 	command -v hdparm >/dev/null 2>&1 || return 1
-	is_ata_device "$dev" || return 1
+	is_ata_device "${dev}" || return 1
 	log "hdparm secure erase"
-	hdparm --security-erase NULL "$dev"
+	hdparm --security-erase NULL "${dev}"
 }
 
 wipe_dev() {
-	local dev="$1"
+	local dev="${1}"
 
 	STARTDATE=$(date +%s)
 	STARTDATESTRING="$(date)"
 
-	log "Begin wiping: $dev"
+	log "Begin wiping: ${dev}"
 	echo ""
 	log "Start date :"
-	log "$STARTDATESTRING"
+	log "${STARTDATESTRING}"
 	echo ""
 
-	if wipe_with_blkdiscard_secure "$dev"; then
+	if wipe_with_blkdiscard_secure "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_blkdiscard_zero "$dev"; then
+	if wipe_with_blkdiscard_zero "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_dd "$dev"; then
+	if wipe_with_dd "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_ddrescue "$dev"; then
+	if wipe_with_ddrescue "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_dd_rescue "$dev"; then
+	if wipe_with_dd_rescue "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_nvme "$dev"; then
+	if wipe_with_nvme "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
 	echo ""
-	if wipe_with_hdparm "$dev"; then
+	if wipe_with_hdparm "${dev}"; then
 		echo ""
-		log "Device $dev wiped."
+		log "Device ${dev} wiped."
 		return
 	fi
 
@@ -257,10 +261,10 @@ wipe_dev() {
 main() {
 	check_args "$@"
 	confirm_root
-	check_device "$1"
-	check_device_not_in_use "$1"
-	confirm_wipe "$1"
-	wipe_dev "$1"
+	check_device "${1}"
+	check_device_not_in_use "${1}"
+	confirm_wipe "${1}"
+	wipe_dev "${1}"
 	print_time
 }