Inside the Mainframe

• Find the stairwell on each floor and go down. On the sixth floor, fix the Unhandled Exception to get the vault key, open the vault, take the source tape, and carry it back to the freight elevator where you came in.
• Move with the arrow keys, WASD, or the number pad (Q, E, Z and C, or Y, U, B and N, go diagonally). On a phone, use the pad, or tap any tile you've seen to walk there.
• Fix a bug by walking into it. Each bug has its own habits: the In sight panel says what the ones near you do.
• Items are numbered 1 to 8: coffee, patch decks, the debugger, the core-dump analyzer, printout maps, restart cards, and from the break room, moldy sandwiches and strong coffee. Walk over things to pick them up.
• Four shifts. Training shift is for the new intern. Day and Swing shift get harder. On the Night shift the lights are low, a bat lives in each wiring closet (walk into it to shoo it; it never hurts you, and nobody hurts it), and the Ghost in the Wire drifts through the walls.
• Machines: walk into a console to read its system log (it shows the stairwell), or into a crashed disk drive to salvage it. Open floor tiles tangle you for a turn. A red pull station sets off a room's halon system: three turns later the room floods, and anything inside, bugs included, takes a beating.
• . or Space waits a turn, > goes down the stairs, ? shows the help. You get energy back slowly on your own, but new bug reports keep coming in, so don't wait too long.
• Your run saves after every move. Each run has a number: start a new run with the same number to play the same building again.

Inside the Mainframe is an original game, inspired by the roguelike genre and by 1970s computing. The computer center, its floors, the bugs and the story are all made up. It borrows the genre's habits (turn-based moves on a grid, floors built fresh for every run, a map that fills in as you explore, and one life per run) and none of any particular game's monsters, items or rules.

Before release it was played thousands of times at each level by an autopilot, checking that every floor can be finished and that no run gets stuck. The playtest numbers are in the game's design notes.