Penguins (order Sphenisciformes, family Spheniscidae) are a group of aquatic flightless birds. They live almost exclusively in the Southern Hemisphere, with only one species, the Galapagos penguin, found north of the equator. Highly adapted for life in the water, penguins have countershaded dark and white plumage, and their wings have evolved into flippers. Most penguins feed on krill, fish, squid and other forms of sea life which they catch while swimming underwater. They spend roughly half of their lives on land and the other half in the sea.

Although almost all penguin species are native to the Southern Hemisphere, they are not found only in cold climates, such as Antarctica. In fact, only a few species of penguin live so far south. Several species are found in the temperate zone, and one species, the Galápagos penguin, lives near the equator.

The largest living species is the emperor penguin (Aptenodytes forsteri):on average, adults are about 1.1 m (3 ft 7 in) tall and weigh 35 kg (77 lb). The smallest penguin species is the little blue penguin (Eudyptula minor), also known as the fairy penguin, which stands around 40 cm (16 in) tall and weighs 1 kg (2.2 lb). Among extant penguins, larger penguins inhabit colder regions, while smaller penguins are generally found in temperate or even tropical climates (see also Bergmann's rule). Some prehistoric species attained enormous sizes, becoming as tall or as heavy as an adult human. These were not restricted to Antarctic regions; on the contrary, subantarctic regions harboured high diversity, and at least one giant penguin occurred in a region around 2,000 km south of the equator 35 mya, in a climate decidedly warmer than today.

Video game addiction (VGA), also known as gaming disorder or internet gaming disorder, is generally defined as a psychological addiction that is problematic, compulsive use of video games that results in significant impairment to an individual's ability to function in various life domains over a prolonged period of time. This and associated concepts have been the subject of considerable research, debate, and discussion among experts in several disciplines and has generated controversy within the medical, scientific, and gaming communities. Such disorders can be diagnosed when an individual engages in gaming activities at the cost of fulfilling daily responsibilities or pursuing other interests without regard for the negative consequences. As defined by the ICD-11, the main criterion for this disorder is a lack of self control over gaming.

The World Health Organization included gaming disorder in the 11th revision of its International Classification of Diseases (ICD). The American Psychiatric Association (APA), while stating there is insufficient evidence for the inclusion of Internet gaming disorder in the Diagnostic and Statistical Manual of Mental Disorders in 2013, considered it worthy of further study.

Controversy around the diagnosis includes whether the disorder is a separate clinical entity or a manifestation of underlying psychiatric disorders. Research has approached the question from a variety of viewpoints, with no universally standardized or agreed definitions, leading to difficulties in developing evidence-based recommendations.