Q:Information: - Ristar, released as in Japan, is a platform game developed by Sonic Team and published by Sega for the Sega Genesis, which released worldwide in February 1995. A Sega Game Gear game, of the same name and genre, "Ristar", was also released, which shared similar themes, while possessing different level design and gameplay mechanics. - A Platform game (or platformer) is a video game which involves guiding an avatar to jump between suspended platforms and/or over obstacles to advance the game. The player controls the jumps to avoid letting the avatar fall from platforms or miss necessary jumps. The most common unifying element of games of this genre is the jump button, but now there are other alternative like swiping in touchscreen. "Jumping", in this genre, may include swinging from extendable arms, as in "Ristar" or "Bionic Commando", or bouncing from springboards or trampolines, as in "Alpha Waves". These mechanics, even in the context of other genres, are commonly called "platforming", a verbification of "platform". Games where jumping is automated completely, such as 3D games in "The Legend of Zelda" series, fall outside of the genre. - Proprietary software is computer software for which the software's publisher or another person retains intellectual property rightsusually copyright of the source code, but sometimes patent rights. - Freeware is proprietary software that is available for use at no monetary cost. In other words, freeware may be used without payment but may usually not be modified, re-distributed or reverse-engineered without the author's permission. Two historic examples of freeware include Skype and Adobe Acrobat Reader. - Icy Tower is a popular freeware computer game by Swedish game developer Free Lunch Design . It is a platform game set in a tower , where the player 's goal is to jump from one '' floor '' to the next and go as high as possible without falling and plunging off the screen . The higher the player 's character climbs , the faster the tower 's floors move downward and the harder the game becomes . By default , the player controls the character using a keyboard . What is the relationship between 'icy tower' and 'proprietary software'?
A:
license