We would like to suggest the first 15 levels: LV 1: CAT - ACT LV 2: DOG - GOD LV 3: GEL - LEG LV 4: END - DEN LV 5: ART - RAT - ART LV 6: AIR - RAID - ARID - RID LV 7: LOUD - DUO - OLD LV 8: MIND - DIM - MID LV 9: LAID - AID - DIAL - LID - LAD LV 10: TURN - NUT - RUN LV 11: LAMP - LAP - MAP - PALM - LAM - PAL LV 12: LATE - TALE - TEAL - LET - ALE - EAT - ATE - TEA - LV 13: EAR - ARE - RAW - WEAR - WARE - AWE - WAR - ERA LV 14: EAT - ATE - TEA - PAT - PAT - TAPE - PEA - APT - APE LV 15: EDIT -