Screenshots of the two visual spellers. The current word was indicated in the box above the speller, and the current symbol was highlighted, (a) Symbol matrix. The column containing the target symbol "B" is intensified. (b) Hex-o-Spell, group level. The group containing the target symbol "B" (group "ABCDE") is intensified, (c) Transition phase. In a short animation, the symbols of the selected group are expanded onto the other discs. (d) Symbol level. The nontarget disc with the symbol "A" is intensified. The empty disc at the bottom is intended as a backdoor for returning to the group level in case the wrong group was selected.