Your goal: Hack into the system by solving a series of number grids. Each grid contains white KEY boxes and green CIPHER boxes. Each box has a unique solution. No two numbers are repeated.
To play: Catch the falling numbers and drop them into the green boxes. Solve the grid by placing the correct number in each box.
Numbers that fall off the bottom of the screen are INTRUSIONS. Wrong numbers also count as intrusions. If you reach the intrusion limit, the game ends.
Each grid represents one level of security in the system. Intrusions are reset to 0 at the beginning of each new level. There are 5 levels per sector (except in sector 1, which only has 4 levels).
As you get further into the system, you'll encounter more challenges (faster numbers, even/odd and reverse numbers) and hazards (/tmp numbers, rotating keys, and viruses). Each sector has a new hazard. The higher you go, the harder it gets. Think fast to outwit the system!