Merlin was created by Bob Doyle, a Harvard PhD. and inventor who had previously worked with NASA. Merlin took the form of a rectangular device about eight inches long and three inches wide. The play area of the game consisted of a matrix of eleven buttons; each button contained a red LED. The array was encased in a red plastic housing, bearing a slight resemblance to an overgrown touch-tone telephone. Four game-selection and control buttons were also placed at the bottom of the unit; a speaker took up the top section. Supporting electronics (including a simple microprocessor) were contained within the shell of the game. Parker Brothers later released Master Merlin with more games, and the rarer Split Second, where all games involve time with a more advanced display, sporting line segments around the dots. Both of these share the same general case shape, and came out a few years after Merlin.
Merlin's simple array of buttons and lights supported play of six different games, some of which could be played against the computer or against another person. A list of games that could be selected includes:
- Tic Tac Toe
- Music Machine
- Echo, a game similar to Simon
- Blackjack 13
- Magic Square, a pattern game
- Mindbender, similar to Mastermind