Helvetica vs. Arial is a cool app made by designers for designers. It teaches your eye for the typographic details and differences between the two most used typeface in teh world: Helvetica and Arial.
Helvetica was designed 1952 by Max Miedinger and runned under the name Neue Haas Grotesk. This font changed fundamentally the whole graphic design. Arial on the other hand is a knock off designed by Microsoft in order to avoid licensing fees. Due to windows, Arial is one of the most used typefaces on personal computers.