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Dr. Brain is a series of educational games made by Sierra On-Line in the 1990s. The objective of each game is solving a series of puzzles in order to proceed further into the game. The series was later picked up by Knowledge Adventure who turned it into a more action-oriented game.
The original two games, Castle of Dr. Brain (1991) and The Island of Dr. Brain (1992), are hybrid puzzle adventure games created by an in-house team at Sierra. After the second game was released, Sierra acquired another company, Bright Star Technology, known for its educational games. The series was turned over to a Bright Star team, explaining the change in direction from the second game to the third. The third and fourth are The Lost Mind of Dr. Brain (1995) and The Time Warp of Dr. Brain (1996).
Dr. Brain is an elderly absentminded professor. The first two Sierra games follow the Dr. Thaddeus Egghead Brain, and the last two follow Dr. Thaddeaus Puzzle Brain the Third. Dr. Brain was 'reincarnated' as Dr. Cranium in Quest for Glory IV (both Dr. Brain and Quest for Glory series are designed by Corey Cole, though Dr. Cranium mentions once that one of his descendants would get "his very own game".). The background information for Dr. Cranium in the Shadows of Darkness Hintbook written by Lori and Corey Cole states that Dr. T. Egghead Brain is Dr. Cranium's great-great grandson.
Knowledge Adventure later released four games based on the original series:
- Dr. Brain Thinking Games: Puzzle Madness (1998) or Puzzleopolis - The first game turns Dr. Brain into a brain sitting in a jar, and casts the player as Dr. Brain's clone, Pro, fighting against the evil Con. The player plays mini-games which are logic orientated to gain devices to duel Con and his flunkies with.
- Dr. Brain Thinking Games: IQ Adventure (1999) or Mind Venture - The second game is a third-person adventure where the player has to find and use objects to restore a trans-dimensional device that has trapped him in a strange dimension filled with plant people and mole-men.
- Dr. Brain: Action Reaction - The third game is played in a first-person perspective, and the player and Dr. Brain have been kidnapped by S.P.O.R.E, an evil organization bent on world domination. Using the three laws of physics, switch flipping, rocket turrets, and the "helping hand" to knock out guards, the player battles through 45 levels to capture the evil Dr. Craven.
- The Adventures of Dr. Brain - Dr. Brain travels through time and space to go on mission to defeat The Hench and his Henchmen. The Hench has dispersed Goopods and Goo Gords all throughout different time eras. You must go to the Industrial and Ancient time eras to destroy Goopods and battle Goo Gords!
 The new series recast Dr. Brain as a twenty-something genius instead of an old mad scientist (though this may be explained by identifying the young man with Pro). In the newer games, there are generally less education-oriented and more problem-solving puzzles, although most are third or first person games involving throwing switches and stunning guards (IQ Adventure and Action Reaction).