A pseudo polyamino is a plane geometric figure formed by joining one or more equal squares edge to edge or to a corner. In this case, the squares are joined at a corner, which means they form a right angle. A right angle measures 90 degrees, so the correct answer is 90.

A polyomino is a shape made by joining squares of the same size edge to edge. When a polyomino is equal to its perimeter, it means that the number of squares in the shape is equal to the total length of its edges. In other words, the area of the shape is equal to the perimeter. This property is known as being "equable".

The correct answer is SquareGraphs because polyominoes are shapes made up of squares, and the graphs of vertices and edges of these shapes can be represented using square grids or graphs.

Free polyominoes are said to be distinct when none of them can be obtained from a rigid transformation of another. In other words, each polyomino has a unique shape that cannot be transformed into the shape of another polyomino by rotations, reflections, or translations. This means that every polyomino is different and cannot be made identical to another through any rigid transformation.

Polyominoes can be distinguished by employing three methods. The first method is by counting the number of squares in the polyomino. Each polyomino has a different number of squares, which allows for differentiation. The second method is by observing the shape and arrangement of the squares within the polyomino. Different polyominoes can have different shapes and arrangements, making them distinguishable. The third method is by considering the orientation of the polyomino. Polyominoes can be rotated or flipped, resulting in different orientations and therefore different polyominoes. These three methods combined allow for the distinction of polyominoes.

Blokus is an example of a board game that uses polyominoes. In Blokus, players take turns placing their pieces on the board, with each piece being made up of multiple connected squares. The goal is to strategically place your pieces in a way that maximizes your territory while blocking your opponents from doing the same. Polyominoes, which are shapes made up of squares connected edge-to-edge, are the fundamental building blocks of the game. Therefore, Blokus is a board game that specifically utilizes polyominoes in its gameplay.

Iwan Jensen is credited with discovering the modern algorithm for enumerating the fixed polyominoes.

A polyomino is known to be "directed" when it contains a square, known as the root, from which every other square can be reached by movements of up or right one square, without leaving the polyomino. This means that there is a clear directionality in the arrangement of the squares, with all squares being reachable in a specific path starting from the root square.

Tetrominoes are the correct answer because they are the seven one-sided polyominoes used in the video game Tetris. Polyominoes are geometric shapes formed by joining squares together, and tetrominoes specifically consist of four squares arranged in different configurations. In Tetris, players must manipulate and fit these tetrominoes together to complete lines and score points. Therefore, tetrominoes are the correct term for the shapes used in Tetris.

Polyominoes have been used in popular puzzles since the late 1900s. This means that they have been used for a long time, dating back to the early 20th century. The use of polyominoes in puzzles has been popular for many decades, and they continue to be used in various puzzle games and challenges even today.