From the deck of the intergalactic space craft, the user can explore the scene trough point and click controls. Clicking on items inside the ship as well as the Star Trek characters, who are depicted as he letters that spell Google (Spock is the 'G', Uhura and Kirk are 'o's, McCoy is the 'g', Sulu is the 'l', the 'e' is an enterprising "red shirt," and Chekov is missing).
Choices trigger sound effects from the original series, and send the Star Trek: Original Series characters from the bridge of the transporter room to a barren planet where a classic Star Trek scene from the "Arena" episode. While the Star Trek episode had Captain Kirk in the fight of his life against the scaly Gorn, here the letter E faces off against what looks like a Pez dispenser with a reptile head. In both the original Star Trek scene and the Google Doodle, however, our hero builds a "Gorn Cannon" out of available materials and defeats his enemy.
The original Star Trek series was created by Gene Roddenberry and aired from 1966 to 1969. The sci-fi epic was original simply titled Star Trek, but was later dubbed Star Trek: The Original Series (TOS) after the original series become a media franchise with multiple TV series and films.
Star Wars: The Original Series had a major influence on popular culture, particularly in its nerdiest corners, and it's no surprise that the show has more than a few fans at Google. Star Trek is frequently cited as an important influence by engineers and designers working with technology. Furthermore, the show's overarching message of morality and equality meshes well with Google famous motto: "Don't be evil."
Here's the full Google Doodle. in case you missed it:
And here's the classic Star Trek: TOS that the Doodle was based on: