- Ms. Pac-Man (Atari 2600) (Internet Archive)
In 1981, a sequel to Pac-Man was introduced in the form of his girlfriend, Ms. Pac-Man. This sequel continued on the “eat the dots/avoid the ghosts” gameplay of the original game, but added new features to keep the title fresh.
- Chemical element (Wikipedia)
A chemical element is a chemical substance that cannot be broken down into other substances. The basic particle that constitutes a chemical element is the atom, and each chemical element is distinguished by the number of protons in the nuclei of its atoms, known as its atomic number. For example, oxygen has an atomic number of 8, meaning that each oxygen atom has 8 protons in its nucleus. This is in contrast to chemical compounds and mixtures, which contain atoms with more than one atomic number.