The games are usually direct unlicensed copies of official NES and Famicom game titles, usually with copyright information removed and sometimes featuring other minor changes. The most commonly found games in NES clones are generally games below 64 K of ROM size and which can be easily split into distinct subgames or levels. As such, "Track & Field" and "Circus Charlie" are present in a large percentage of NES clones, usually blown up to count as 6 or 7 "distinct" games each. "Duck Hunt" (often with its clay shooting mode shown as a separate game) is also a common NES clone feature as they justify the existence of the light gun accessory. Other popular, although less common choices, are "Super Mario Bros." hacks, "Excitebike", "Tetris", "Magic Jewelry" (an unlicensed clone of Columns), older sports titles and miscellaneous platform games. Additionally, some clones incorporate games which, although they may initially appear to be original, are in fact counterfeit copies featuring extensive graphical (and sometimes audio) modifications. Examples of this include "UFO Race", based on Nintendo's "F-1 Race", "Pandamar" (also known as simply "Panda"), based on "Super Mario Bros.", "Ladangel", based on Hudson Soft's "Challenger" and "UFO Shoot", based on "Duck Hunt".