What's That Flag? APP
It can search in more than 200 flags for criteria such as: the colors of the flags, the number and the orientation of the stripes, the presence/absence of circles, triangles, crosses, stars, emblems, crescent, canton, dencety line, border,...
You can also perform text searches, which will lookup in the countries names, capitals, alpha3 code.
You can filter results by continent.
Voice search is also supported on some devices.
For each country, the app tells you about the capitale and continent and shows details of/about its flag (ratio, adoption date,...), provides direct access to a lot of information about the country (location on a world map, population, language, area, currency, history...), through its Wikipedia page.
And of course you can revise or learn the flags, countries and capital with fun using a customizable QUIZ !