Option 0 - Characters are based on darkness:

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

Option 1 - Randomized characters, based on darkness:

览觋KK技儋XX谮KK哪览XX儋谮WW苘
哪XX亮哪WW儋儋谮览览儋览痧KK
觋哪排WWWW觋悙痧技XXXX览XX
WW亮苘WW谮帋亮哪亮谮览儋KK
KK哪苘WW览览WW觋亮WW儋亮览
排技排櫃湝XXWW亮排WW谮WW哪KKXX
儋谮WW排XX苘览哪亮排览哪KKWW
谮苘苘技XX谮KK览览痧WW排
哪亮儋WWWW亮技排痧WWXX苘哪
XXKK觋沣苘苘XX苘技技觋觋儋
儋XX儋KK哪儋KK儋哪灋行觋觋谮排
谮儋WW谮苘谮觋弿弿排WWXX览技
儋儋觋苘苘儋崓棗寣览痧儋览WW哪
XX觋技XX亮谮XX儋排觋WW谮儋苘
谮亮览哪XXWW排XX哪XXKKXXKK觋技

Option 2 - Use only one pair of characters (%%) :

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