diff --git a/captcha/experimental.sh b/captcha/experimental.sh
index 7fccd36..bd8d3d4 100755
--- a/captcha/experimental.sh
+++ b/captcha/experimental.sh
@@ -1,5 +1,20 @@
 #!/bin/bash
 
+# Copyright © 2021 Adrien Bourmault (neox@a-lec.org)
+# Copyright © 2021 Echolib (echolib@dismail.de)
+
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+# GNU Affero General Public License for more details.
+# You should have received a copy of the GNU Affero General Public License
+# along with this program. If not, see <https://www.gnu.org/licenses/>.
+
 # This script is an example captcha script.
 # It takes the text to recognize in the captcha image as a parameter.
 # It return the image binary as a result. ejabberd support PNG, JPEG and GIF.
@@ -14,121 +29,140 @@
 # It is NOT compliant with ImageMagick forks like GraphicsMagick.
 
 INPUT=$1
-
-TRANSFORMATIONS=(INTRUS SOMME)
+LENINPUT=${#INPUT}
 DIGIT=(zéros uns deux trois quatres cinqs six septs huits neufs dix)
 
-if test -n ${BASH_VERSION:-''} ; then
-    get_random ()
-    {  
-	R=$RANDOM
-    }
+# Loop 10 times (should be enough) to check if a TARGET number is in INPUT
+GENERATE__NOTIN() {
+for i in {1..10}
+do
+   FALSENBR=`seq 1 9 | sort -R | head -n 1`
+   ! [[ $INPUT =~ $FALSENBR ]] \
+      && break
+done
+}
+
+#=====
+# Modules
+#=====
+
+# REPLACE a random number in INPUT by another one Randomized
+REPLACE() {
+NAME="REPLACE"
+PLACE=`seq 1 6 | sort -R | head -n 1`
+TARGET=`echo "$INPUT" | head -c $PLACE | tail -c 1`
+
+GENERATE__NOTIN
+NAME+="-$FALSENBR-$TARGET"
+NEWINPUT=${INPUT//$TARGET/$FALSENBR}
+INSTRUCTIONS1="Remplacez les ${DIGIT[FALSENBR]} par les ${DIGIT[TARGET]}"
+}
+
+# REVerse INPUT. Ask to Add first or last number in random. 
+REVERSE() {
+NAME="REVERSE"
+RFL=`seq 1 2 | sort -R | head -n 1` # Rand First (1) or Last (2)
+ADDNBR=${DIGIT[ADDNBR]}
+
+for ((i=$LENINPUT-1;i>=0;i--))
+do
+   NEWINPUT="$NEWINPUT${INPUT:$i:1}"
+done
+
+if (( $RFL == 1 ));then
+   ADDNBR="${INPUT:0:1}"
+   NAME+="_FIRST"
+   NEWINPUT=${NEWINPUT:0:$LENINPUT-1} # Do not show first INPUT NBR
+   INSTRUCTIONS1="Écrivez le chiffre ${DIGIT[$ADDNBR]} puis"
+   INSTRUCTIONS2="Recopiez de DROITE à GAUCHE ←"
 else
-    for n in `od -A n -t u2 -N 64 /dev/urandom`; do RL="$RL$n "; done
-    get_random ()
-    {  
-	R=${RL%% *}
-	RL=${RL#* }
-    }
+   ADDNBR="${INPUT:$LENINPUT-1:1}"
+   NAME+="_LAST"
+   NEWINPUT=${NEWINPUT:1:$LENINPUT-1} # Do not show last INPUT NBR
+   INSTRUCTIONS1="Recopiez de DROITE à GAUCHE ←"
+   INSTRUCTIONS2="Terminez par le chiffre ${DIGIT[$ADDNBR]}"
 fi
-
-INTRUS()
-{
-    LENGTH=${#INPUT}
-    NUMBERS=$(echo $INPUT | grep -o . | tr '\n' ' ')
-    SORTED_UNIQ_NUM=$(echo "${NUMBERS[@]}" | sort -u | tr '\n' ' ')
-    INTRUS=-1
-    
-    for i in 1 2 3 4 5 6 7 8 9
-    do
-        if [[ ! " ${SORTED_UNIQ_NUM[@]} " =~ " ${i} " ]]; then
-            INTRUS=$i
-            break
-        fi
-    done
-    
-    # Worst case
-    if [[ $INTRUS -eq "-1" ]]
-    then
-        echo Tapez "$INPUT |sans changement"
-        return
-    fi
-    
-    for num in ${NUMBERS[@]}
-    do
-        get_random
-        R=$(($R % 100))
-             
-        if [[ $R -lt 60 ]]; then 
-            NEWINPUT=${NEWINPUT}${num}${INTRUS}
-        else
-            NEWINPUT=${NEWINPUT}${num}
-        fi
-    done
-    
-    get_random
-    R=$(($R % 100))
-    
-    if [[ $R -lt 50 ]]; then
-        echo "Tapez ce nombre en enlevant les ${DIGIT[$INTRUS]} | $NEWINPUT"
-    else
-        echo "Saisissez ce nombre sans les ${DIGIT[$INTRUS]} | $NEWINPUT"
-    fi
+NAME+="-$ADDNBR"
 }
 
-SOMME()
-{
-    get_random
-    RB=$(($R % 5))
-    get_random
-    RA=$(($R % 10 * (10 ** $RB)))
-    
-    if [[ $(($INPUT % 2)) -eq 0 ]]; then
-        A=$(($INPUT - $RA))
-        B=$RA
-    else
-        B=$(($INPUT - $RA))
-        A=$RA
-    fi
-    
-    get_random
-    R=$(($R % 100))
-    
-    if [[ $R -lt 25 ]]; then
-        echo "Tapez le résultat de | $A + $B"
-    elif [[ $R -lt 50 ]]; then
-        echo "Sommez | $A et $B"
-    elif [[ $R -lt 75 ]]; then
-        echo "Additionnez | $A et $B"
-    else
-        echo "Saisissez le résultat de | $A + $B"
-    fi
+# Add FALSE NBR to INPUT at three randomized place
+NOTIN() {
+NAME="NOTIN"
+GENERATE__NOTIN
+PLACE=(`seq 0 $((LENINPUT-1)) | sort -R | head -n 3 | sort -n`)
+for i in `seq 0 $((LENINPUT-1))`
+do
+   (( $i == ${PLACE[0]} )) \
+      && NEWINPUT+="$FALSENBR"
+   (( $i == ${PLACE[1]} )) \
+      && NEWINPUT+="$FALSENBR"
+   (( $i == ${PLACE[2]} )) \
+      && NEWINPUT+="$FALSENBR"
+   NEWINPUT="$NEWINPUT${INPUT:$i:1}"
+done
+NAME+="-$FALSENBR"
+INSTRUCTIONS1="Recopiez sans les ${DIGIT[FALSENBR]}"
 }
 
-get_random
-RAND_INDEX=$(($R % ${#TRANSFORMATIONS[@]}))
+# Take a random NBR from INPUT. Calculate X
+CALCUL() {
+PLACE=`seq 1 $((LENINPUT)) | sort -R | head -n 1`
+TARGET=`echo "$INPUT" | head -c $PLACE | tail -c 1`
+NEWINPUT=${INPUT//$TARGET/X}
 
-INSTRUCTIONS=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 1)
-INSTRUCTIONS2=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 3)
-TEXT=$(echo "$(${TRANSFORMATIONS[$RAND_INDEX]})" | cut -d "|" -f 2)
+RC=`seq 1 2 | sort -R | head -n 1` # 1 = - | 2 = +
+if (( $RC == 1 ));then
+   FALSENBR=`seq $TARGET 10 | sort -R | head -n 1`
+   RESUME=$(( FALSENBR - TARGET ))
+   INSTRUCTIONS1="Calculez: $FALSENBR moins $RESUME. Copiez..."
+   NAME="CALCULM-$FALSENBR-$RESUME"
+else
+   FALSENBR=`seq 1 4 | sort -R | head -n 1`
+   if (( $FALSENBR <= $TARGET ));then
+      RESULT=$(( TARGET + FALSENBR ))
+      RESUME=$(( TARGET - FALSENBR ))
+      INSTRUCTIONS1="Calculez: ${DIGIT[FALSENBR]} + ${DIGIT[RESUME]}. Copiez..."
+      NAME="CALCULP-$FALSENBR-$RESUME"
+   else
+      RESULT=$(( FALSENBR - TARGET ))
+      RESUME=$(( TARGET - RESULT ))
+      INSTRUCTIONS1="Calculez: ${DIGIT[RESULT]} + ${DIGIT[RESUME]}. Copiez..."
+      NAME="CALCULP-$RESULT-$RESUME"
+   fi
+fi
+INSTRUCTIONS2="...en remplaçant chaque X par la somme"
+}
+
+#=====
+# Choose a random module
+#=====
+
+MODULES=(CALCUL NOTIN REPLACE REVERSE)
+NBRMODULES=${#MODULES[@]}
+RMODULE=`seq 0 $((NBRMODULES-1)) | sort -R | head -n 1`
+eval "${MODULES[RMODULE]}"
+
+TEXT="$NEWINPUT"
+CHAPRILURI="$HOME/Images/Captcha/${NAME}_${NEWINPUT}_${INPUT}.png"
 
 convert -size 300x70 xc:none -pointsize 20 \
 	\( -clone 0 -fill black \
 	-stroke black -strokewidth 1 \
-	-font Helvetica-Narrow -annotate "0x0+0+0" "\n $INSTRUCTIONS" \
-	-font Helvetica-Bold  -annotate "0x0+0+22" "\n  $TEXT" \
-	-font Helvetica-Narrow -annotate "0x0+0+44" "\n $INSTRUCTIONS2" \
+	-font Helvetica-Narrow  -annotate "0x0+0+0"     "\n $INSTRUCTIONS1" \
+	-font Helvetica-Bold    -annotate  "0x0+0+22"   "\n   $TEXT" \
+   -font Helvetica-Narrow  -annotate "0x0+0+44"    "\n $INSTRUCTIONS2" \
 	-roll +$ROLL_X+0 \
 	-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
 	-roll -$ROLL_X+0 \) \
-	-flatten -crop 300x70 +repage -quality 500 -depth 11 png:"/var/lib/ejabberd/chapril_captchas/EXPERIMENTAL_$(date "+%Y-%m-%d-%H%M%S")_${INPUT}.png"
+	-flatten -crop 300x70 +repage -quality 500 \
+   -depth 11 png:"$CHAPRILURI"
 
 convert -size 300x70 xc:none -pointsize 20 \
 	\( -clone 0 -fill black \
 	-stroke black -strokewidth 1 \
-	-font Helvetica-Narrow -annotate "0x0+0+0" "\n $INSTRUCTIONS" \
-	-font Helvetica-Bold  -annotate "0x0+0+22" "\n  $TEXT" \
-	-font Helvetica-Narrow -annotate "0x0+0+44" "\n $INSTRUCTIONS2" \
+	-font Helvetica-Narrow  -annotate "0x0+0+0"  "\n $INSTRUCTIONS1" \
+	-font Helvetica-Bold    -annotate "0x0+0+22" "\n   $TEXT" \
+	-font Helvetica-Narrow  -annotate "0x0+0+44" "\n $INSTRUCTIONS2" \
 	-roll +$ROLL_X+0 \
 	-wave "$WAVE1_AMPLITUDE"x"$WAVE1_LENGTH" \
 	-roll -$ROLL_X+0 \) \