To gain entry to the Training Room in Missile Command Delta, you must first locate the keypad within the Training Lounge. This area becomes accessible once initial power systems are restored and several preliminary missile defense scenarios have been successfully completed. You'll find the Training Lounge by turning right from the underground bunker's entrance and entering the first door on your right. Keep an eye out for Victor, who will also be present in this vicinity.
For those who prefer to solve the puzzle independently, a critical hint lies in the immediate surroundings of the keypad. Observe the vibrant, circular indicators positioned adjacent to the keypad itself. Their sequence—blue, red, and yellow—is not arbitrary but serves as a vital clue to the solution. These colors correspond directly to elements elsewhere in the lounge, holding the key to unlocking your progress.
Once you've identified the colored indicators, pivot your gaze towards the wall directly opposite the keypad. There, you'll discover a series of rocket posters, each prominently featuring one of the colors seen on the keypad's indicators: red, yellow, and blue. The trick to solving this puzzle is to count the fins on each rocket corresponding to these specific colors. The numerical value derived from the fin count of each colored rocket, when arranged in the precise order of the keypad's colored dots—blue first, then red, and finally yellow—will reveal the correct three-digit access code.
After diligently counting the rocket fins according to the color sequence, the definitive access code for the Training Room keypad is revealed: 6-8-4. Inputting this sequence into the keypad will grant you immediate entry.
With the Training Room door now open, your journey in Missile Command Delta continues. Inside, you'll encounter three computers, each presenting new missile defense puzzles that must be overcome. Furthermore, a locked cabinet in this same room holds additional secrets, accessible only after solving a related puzzle on a nearby terminal. Your success in deciphering these challenges will further enhance your capabilities and prepare you for even greater strategic endeavors.