"I see now!" (3)
(Other definitions for aha that I've seen before include "Cry of surprise" , "Triumphant cry" , "Surprised expression" , "Cry of triumph" , "Exclamation of discovery or triumph" .)
(Other definitions for gotcha that I've seen before include "claim to have made conquest?" , "You've been caught" , "You're caught - I understand you" , "I've trapped you!" , "cry of apprehension" .)