Level codes
Level 2: AAJIHGDDC
Level 3: CGGHDGGDG
Level 4: HDICICCII
Level 5: IDHEHDGCC
Level 6: IJIIDIHEC
Level 7: CFDFEFEFJ
Level 8: JIIJIIIIC
Level 9: AAAABAAAA
Level 10: CCGDGBBBB
Level 11: HHIAAJJIG
Level 12: GGDDJJHFD
Level 13: JIECBFGFF
Level 14: HGGEDDCCB
Level 15: HHHGFGDCC
Level 16: till
Level 18: IHDCHGHFF