ConnectFour Studio

ConnectFour Studio is a free, offline Connect Four program: play against the computer, analyse positions and run engine-versus-engine matches. It is the Android version of the desktop program of the same name, with the same engine, levels, help and texts.

Engine

• Perfect play: a Kotlin port of the BitBully solver by Markus Thill (bitboards, MTD(f), transposition table) with the 12-ply opening book with distances – identical results to the original C++ engine
• 15 levels: 0 Loser (joke level), 1 Random … 14 Perfect, defined by (p, s, w): share of perfect moves, loss guard and win guard
• Two custom levels User (1) and User (2) with your own (p, s, w)

Analysis

• Evaluation row under the board: win / draw / loss for every column and the number of stones until the end
• Permanent analysis after every move, one-off evaluation of all moves
• Info box with depth, value, nodes, time, speed and source (book or computed)

Game modes

• Human vs. computer (the computer can also open), two players, computer plays out the position
• Computer-computer match with up to 10,000 games, colour swap, three speeds, Elo difference and copyable result
• Session score human vs. computer per level with Elo estimate
• Random start positions with 1–9 stones and a chosen result

More

• 20 boards with matching stones, ghost stone, drop animation, last move and winning line marked
• Load and save positions as .4gp files (compatible with the desktop version), quick save
• Detailed help with search and zoom, user interface in English, German, French, Spanish, Dutch and Italian
• Portrait and landscape, phones and tablets, keyboard shortcuts with a hardware keyboard
• No permissions, no internet access, no ads, no tracking

License: GNU AGPL v3. Engine: BitBully by Markus Thill (AGPL v3), opening book: bitbully-databases (MIT).

Fix for Android 15 and newer: the top row of the board and the status line were hidden behind the title bar and the system bars (edge-to-edge display).