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Games

Universal Gaming contains eleven games across puzzle, solitaire, strategy and logic. Every game has a How to play sheet available from the hub and from the in-game help button. The whole interface is translated into English, German, Spanish, French and Italian.

Game list

Game	Type	Highlights
Sudoku	Puzzle	Five difficulties, infinite uniquely solvable puzzles, notes, hints, undo/redo, statistics, resume
Killer Sudoku	Puzzle	Dashed cages with sum targets, cage uniqueness, five difficulties, separate saves and records
Mahjong	Tile matching	144 tiles on a stacked board; free pairs only, hints and undo, resume, guaranteed-solvable deals (verified before dealing), matched pairs fade out
Klondike	Solitaire	Draw-three, seven columns, drag or tap to move, dynamic fan, rank + suit corners, card counts on stock and waste, verified solvable deals, resume
Classic Solitaire	Solitaire	Draw-one Klondike for a more relaxed game, drag or tap, verified solvable deals
Spider	Solitaire	One-, two- or four-suit Spider; build eight complete runs, drag or tap
FreeCell	Solitaire	Eight columns, four free cells, multi-card moves, drag or tap, verified solvable deals
Pyramid	Solitaire	Pair exposed cards that add up to 13; kings clear alone; every deal is solvable
TriPeaks	Solitaire	Clear three peaks by chaining cards one rank above or below; every deal is solvable
Chess	Strategy	Computer (four strengths), local two-player, or online by username; full rules, drop-down move history with fallen figures, pending invites in the news sheet, resume for offline games
Minesweeper	Logic	Beginner, Intermediate and Expert (30 wide × 16 tall) boards; first-click safety, flood reveal, flag mode, chording, resume, board rotates to match the screen

Saving and resuming

Every game saves an unfinished session automatically when you leave the screen or background the app, and clears it once the game is finished:

• Sudoku / Killer Sudoku — board, notes, timer, mistakes and hints.
• Minesweeper — difficulty, mines, flags and revealed cells.
• Mahjong — the exact tile layout and move count.
• Klondike, Classic Solitaire, Spider, FreeCell, Pyramid, TriPeaks — the full deal and move count; Spider also remembers the suit count.
• Chess — offline games are replayed from their UCI move list; online games live on the server.

Unfinished sessions are also included in account save backups, so restoring a backup brings games in progress back on a new device.

Sudoku and Killer Sudoku

Both variants generate puzzles on-device. A puzzle is only accepted after a solver confirms it has exactly one solution.

• Classic Sudoku uses the standard 9×9 rules.
• Killer Sudoku adds dashed cages. Every cell belongs to exactly one cage, digits never repeat inside a cage, and each cage sums to its target.
• Difficulties: Easy, Medium, Hard, Expert and Master.
• Notes mode, hints, undo/redo, mistake highlighting and peer highlighting are available.
• Games are saved automatically and can be resumed from the game's home screen.
• Statistics and records are tracked separately for each variant and difficulty.

Sudoku keyboard shortcuts

Key	Action
1–9, numpad	Enter a digit
Arrow keys	Move selection
Backspace / Delete	Erase
N	Toggle notes
H	Hint
P	Pause / resume
Ctrl+Z / Cmd+Z	Undo
Ctrl+Shift+Z / Cmd+Shift+Z	Redo
Ctrl+Y	Redo on Windows/Linux

Shortcuts are disabled while a dialog or the settings sheet is open.

Solitaire controls

• Tap a card to select it, then tap a destination.
• Double-tap a face-up card to send it to a foundation or free cell where supported.
• Use Undo to step back.
• Klondike and Classic Solitaire share the same engine but use different draw counts.
• Spider supports 1, 2 and 4 suits.
• FreeCell supports multi-card moves when enough free cells and columns are available.
• New Klondike, Classic Solitaire and FreeCell deals are checked with a bounded solver while they are dealt; a deal the solver cannot prove winnable is thrown away and replaced, so a new game can be finished. Spider keeps random deals.
• Pyramid pairs cards that total 13; both cards leave the board together, and a King clears by itself.
• TriPeaks allows wrapping sequences (King → Ace and Ace → King) and tracks the best series.

Mahjong

• Match two free tiles with the same face.
• A tile is free when nothing covers it and at least one side is open.
• Deals are generated in a guaranteed solution order, so every board can be cleared.
• Hint highlights a playable pair.

Chess

Three modes:

1. Play computer — you are White; the computer replies automatically.
2. Local multiplayer — two players share the device.
3. Online by username — requires an account and the backend's chess feature.

The engine implements castling, en passant, promotion, check, checkmate, stalemate, threefold repetition, the fifty-move rule and insufficient material. Online moves are validated server-side with chess.js; the client is never trusted for turn order or legality.

Useful actions:

• Mode changes the game type.
• White pieces use the hollow glyph set painted white with a dark contour; black pieces use the filled set. The filled pawn (U+265F) is an emoji codepoint and would be drawn as a colour emoji, which is why the white figures avoid it.
• The board is sized so it is always fully visible: by the window height and by the width left over next to the move history, which keeps a 320 px minimum.
• History shows the move list as a drop-down with one move per line: move number, figure, from → to squares, the captured figure and +/# markers. The fallen figures of both sides are listed underneath.
• Flip rotates the board.
• Undo is available in computer and local modes.
• New starts a new game; online matches use Leave.

Difficulty menu

The number keys are a 3 x 3 pad mirroring the box. Keys are square on tablet, desktop and web (capped at 104 px, block centred), and taller on a phone - about 74 px, scaled with the window height - so a digit is never a narrow strip. The remaining-count badge sits in the corner of each key.

The secondary actions - undo, redo, erase, notes, hint - share one slim row of 44 px targets, because they are used far less than the numbers.

The five difficulties are laid out three across with the short row centred, so they read as one block on a phone as well as on a desktop window. Three cards per row switch to a compact type scale so nothing is truncated.

Figures

The figures are drawn from a font that ships with the app (a subset of Noto Sans Symbols 2), so both colours share one set of metrics on every platform. White pieces use the hollow glyphs with a dark contour, black pieces the filled ones; neither depends on what the device has installed. In dark mode the black figures get a light rim - without it they vanish on the dark move history, the captured-pieces row and the promotion dialog. The board opts out of the rim because its squares are light in every theme.

Online matches

An online match tells the board which side you play. Black opens with the board turned around, own pieces at the bottom; it happens once per match, so the Flip button keeps working and the poll cannot undo it.

Learning path

The Strategy section carries a Learn chess card next to the board, and the chess header has a school button. Eight lessons unlock one after another:

1. The pawn - pushing two squares from home, capturing diagonally
2. The rook - sliding lines and the back-rank mate
3. The bishop - diagonals and square colours
4. The queen - rook plus bishop, and Scholar's mate
5. The knight - the L-shaped jump and forks
6. The king and check - escaping check safely
7. Castling and promotion - the two special moves
8. Finishing the game - queen mate and the two-rook ladder

Each step is a small position with a task. Tap a piece, tap a highlighted square; a wrong move is taken back and does not count, and every step has a hint. Solving a step shows the explanation, finishing a lesson unlocks the next one and the whole path ends in a game against the computer.

Progress is stored on the device (universal_gaming.chess.lessons.v1), the hub card shows how many lessons are done, and Restart the learning path clears it without touching saved games.

Minesweeper

• Beginner, Intermediate and Expert difficulties.
• The first reveal is always safe.
• Tap to reveal; long-press or right-click to flag.
• Flag mode in the bottom bar swaps tap behaviour so taps place and remove flags. Tap it again to go back to revealing.
• Tap a revealed number to chord when the correct number of neighbouring mines are flagged.
• A live timer and mine counter are shown in the header.

Leaderboard game IDs

The competitive leaderboard ranks ten solo games. Chess is excluded.

Game	ID
Sudoku	sudoku
Killer Sudoku	killer-sudoku
Mahjong	mahjong
Minesweeper	minesweeper
Klondike	klondike
Classic Solitaire	classic-solitaire
Spider	spider
FreeCell	freecell
Pyramid	pyramid
TriPeaks	tripeaks