It's locked. You're taunted by characters that keep calling you Monkey as you try to crack the code that unlocks the case. Pull the lever, put up with the name calling and pick the correct combination of colored spheres to fill the empty circles.
Find the right combinations for each lock, and you'll win and open the case, revealing its secrets.
On the right side of the panel, numbers appear to let you know how clever your choices are. You get 10 guesses to decode each lock, but watch out for monkey wrenches, which can disrupt the game.
You can also win hints for solving the codes. The full version features over 100 levels of increasing difficulty. If you're a registered user of an earlier version of Enigma, you can get an upgrade for $7.50. It includes a copy of the game on CD.
For more information, including on later updates, please read the documentation or visit the home page.