you don't need invisible chars. Just use a different text direction. e.g. decipher this message as its written bottom-to-top, RTL ``` t_____s s_____i e___s

you don't need invisible chars. Just use a different text direction. e.g. decipher this message as its written bottom-to-top, RTL ``` t_____s s_____i e___s_h t_a_i_T ``` (swap underscore with a space)