Fill Gates

About Fill Gates

Fill Gates takes the kind of logic-gate puzzle you might find in a comic book or an electronics class and turns it into a daily game. Its maker, posting it on Hacker News in October 2026, said the idea came from a puzzle in a comic book and the wish to solve more of them without the tedium.

Each puzzle is a small circuit. At the top is a row of input switches, each 0 or 1; wires lead down through gates to an output register, and under it sits the target. You click switches to flip them, and the outputs update as current flows through the gates. The goal is to make the outputs match the target in as few flips as possible, so the real work is reasoning back from the target before you touch anything. A quick reference panel lists the truth table of every gate used in that day's circuit, and you can press any part of the board to inspect it.

The counter at the top tracks flips, hints and time. A tutorial walks through the basics, hints are there if you stall, and undo, redo and reset let you experiment. When you finish, a share card gives the puzzle number, its difficulty band, your result and your time.

A new numbered circuit arrives every day at midnight UTC, the same for everyone, with harder boards midweek and on Sundays. The archive keeps every earlier puzzle, and a stats page tracks your record. It suits players who like Boolean logic or programming, and anyone who enjoys working a puzzle backwards from its answer.

How to play Fill Gates

1. Open fillgates.com; the tutorial explains the controls on your first visit.
2. Read the target row under the outputs and the gates between inputs and outputs.
3. Work out which inputs each output depends on, using the quick reference truth tables.
4. Flip input switches until every output matches the target, using as few flips as you can.
5. Share your result, or open the archive to play earlier days.

Screenshots

Tips

• Plan before you flip: every flip counts against your score, so reason from the target back to the inputs first.
• Start with outputs fed by a single gate, such as a NOT, and fix those inputs before the shared ones.
• An XOR flips its output whenever either input changes, so use it to correct one bit without touching the rest.
• Press any gate or wire to inspect it when a large circuit gets crowded.

Questions