Most were based on various ways numbers could be read in Japanese.
Examples are With the rapidly falling prices of cell phones in the mid 1990s, young people began experimenting with the short message service that the mobile phone companies started offering.
One example deals with the astrological symbol for Libra (♎).
A sentence like "I have a test today\" (translated) might mean that he or she didn't study enough, or that the test itself is depressing.
Some of these usages disappeared as suitable icons were made but these newly made icons also acquired a usage not originally intended.
Older arcade-style games became particularly popular on mobile phones, which were an ideal platform for arcade-style games designed for shorter play sessions.
Graphics improved as handsets became more powerful, as demonstrated by the mobile version of Ridge Racer in 2003, though such titles typically cost twice as much as other mobile games.
Namco began attempting to introduce mobile gaming to Europe in 2003.
Other mobile games released in 2003 included a Tamagotchi-like virtual pet game by Panasonic where the pet can be fed with photos of foods taken with a camera phone.
, literally "portable telephones," and are often known simply as keitai.
Much of the Japanese population own cellular phones, most of which are equipped with enhancements such as video and camera capabilities.
Paging devices used in the late 1980s to early 1990s predate mobile phones and paved the way for the popularity of the phones among teenagers.
Pagers could only display numbers and were intended to alert the owner that they had received a call from a certain phone number, but teens quickly began using numeric messages to communicate many things, including greetings and everyday emotions.
The use of mobile phones to make calls on public transport is frowned upon, and messages asking passengers not to make calls and to switch their phones to silent mode ("public mode" or "manner mode" in Japanese) are played frequently.