Some time in the recent past, the main computer of a big corporation went mad due to some electrical disturbance. It gained control over its operator and began to influence other employees. Your mission is to find the main frame, defeat the operator and return to the lobby alive.
Mission: Mainframe is a shareware variation of Wizard’s Castle, a mix of a board game and role-playing, set in a bizarre contemporary / sci-fi environment.
Before beginning the game, you first create your character. You may choose one of four character types which differ in their D&D-like vital stats. As in other RPGs, the stats may be increased by gathering experience. You then start in the lobby of the corporation, where you can buy some basic equipment by spending chips and bytes (instead of gold) on such useful items as Junk Food (which is very important, otherwise you’ll starve quickly), Strategies (corresponding to magic spells in fantasy RPGs) and Office Supplies (replace weapons and armor, thus assisting you in dealing with reluctant corporate employees).
Other things you can do in the lobby is go the Health Club, where you can build up your stats, as well as restore your Power & Plans (the power level represents hit points, and plans are needed to use strategies—e.g., spell points). Finally, you can start the real game by taking the elevator to other floors.
The company is located in a thirty floor building. Each floor is divided into an 8x8 grid of squares. Each square may contain something, like employees you have to deal with, or file cabinets which may contain helpful items. As the contents of the squared is determined randomly at the beginning, each game is different. Depending on the difficulty level you chose at the beginning of the game, you can see the contents of the squares, or you have to move onto it to know what it contains.
When you meet an employee, you can deal with him in several ways, for example trying to bribe him, fight him, use a strategy, evade him, trick him, or try to distract him by making a phone call. The success of all these actions depends on different statistics, both of you and the employee. There are 24 different types of employees, and it’s your task to find out how best to deal with each of them. When you successfully deal with an employee, you gain experience and can raise your grade (level), which increases your survival chances in the higher floors, where the employees get more and more powerful.
The file cabinets may contain chips and bytes as well as items like office supplies or beverages. Some of those are helpful, some are harmful (poison)—and some can make you drunk. Luckily, you can first take a sip from a drink, getting a hint about what it may be. As some cabinets are trapped, you also should be careful with them.
The task is complicated by the lights which sometimes go out. To restore light, you have to light a match (which can be taken from some employees) and find a fuse box. Also, you have to get special key cards to get beyond floor 10 and floor 20 by defeating bosses who guard them.
At any time, you can get back to the elevator and lobby, where you can sell your treasures, rest and buy new supplies. You can also quit the game here, getting the opportunity to save your character first.