Phase is heavily celestial in theme with moons, stars, and astronomical events such as: blue moons, meteor showers, and eclipses.
Gameplay is comprised on playing moon phase cards on a gameboard to make pairs and build moon phase sequences. There are also wildcards which can change aspects of gameplay; for instance: getting a second turn, scoring more points for pairs, removing cards from the board, and everyone discarding their hand.
To keep track of points, players use a pool of star tokens to denote which pairs or sequences they made. Other players may steal points by making a new pair or by adding to a sequence. Once a board is full, you gain any star tokens of your color and add them to the ones you've won during play. The goal of the game is to have the most star tokens (points).
—description from the designer