Launch Codes Game

Each wave opens with a launch code, a row of digits at the top of the sky, for eight seconds. Then the digits go dark, and saucers come down asking about the code by place: the fifth digit, the third plus the seventh, and later their product or difference. One launch gantry stands on the ground, over six chambers that each hold a rocket and an answer. Fire the right answer before the saucer lands. You have to hold the places, not just the digits.

How to play

1. A wave starts with a launch code of 8 digits. You have 8 seconds to memorize it before it goes dark.
2. Saucers come down, each asking about the code by place. In the first wave a saucer asks for one digit, such as Digit 5. From wave 2 it asks for the sum of two digits, such as 3rd + 7th, and from wave 4 also their product or their difference.
3. The lowest saucer is the target, with a ring round it. Tap another saucer to aim at it instead.
4. Tap the chamber that holds the target's answer. Its rocket is loaded and fired, and the right one destroys the saucer.
5. A wrong answer jams the launcher for a moment, drops the saucer a step and shows the working under it, such as 4 + 2 = 6, so you can repair your picture of the code.

Every answer in the chambers belongs to a saucer of the wave, and a wave has more saucers than chambers, 7 in the first wave and up to 12 later, so an answer can come down twice, asked a different way. A saucer takes 16 seconds to reach the ground in the first wave and a little less in each wave after it, down to 8 seconds. Every 4 waves the code grows longer, from 8 digits to 10 and then 12. A difference is never below zero: it names the place with the larger digit first.

You have three shields, and a saucer that reaches the ground costs one. On a keyboard, press 1 to 6 for the chambers as they are numbered, and the left and right arrows to change the target. Escape or Space pauses, and pausing hides the code.

Scoring

The sooner you know the answer, the more a saucer is worth.

• A saucer destroyed with no wrong answer scores 100, plus up to 100 more for how high it still is.
• A saucer destroyed after a wrong answer showed its working scores 20.
• A wave with no wrong answer and no landing adds 250.

Your five best scores are saved in this browser, with the wave each game reached. In practice, a saucer that lands costs no shield, so the game goes on until you end it from the pause screen. Practice games are not saved.

How to remember the code

Eight digits are more than most people hold by repeating them. Memory athletes turn digits into pictures instead: with the Major System, 48 might be a roof and 17 a tack, and four pictures in a row hold the whole code. Place the pictures along a short route in a memory palace and you know which digit is third and which is seventh, which is what the saucers ask. See how to create mnemonic images for more ways to build them.

Try our other free memory games, such as Pi Runner for long numbers or Prime Factor Cannon for arithmetic.