Three-Check and King of the Hill preserve orthodox move legality while adding a second way to win.
This creates a useful family:
ordinary checkmate still matters + an additional legal objective can end the game first.
The objective must be encoded explicitly because board position alone may no longer describe the complete game state.
Orthodox Mate Plus Additional Objective
These variants preserve orthodox legal movement/checkmate while adding another legal win condition. The first completed win condition under the rules ends the game.
Objective Precedence
If a legal move simultaneously reaches the variant objective and changes check/mate status, apply the implementation's explicit termination rule. Do not infer precedence from orthodox chess alone.
Legal Winning Move
A winning objective move must itself be legal under the ruleset—for example a KOTH king cannot enter an attacked center square.
Draw Rules Must Be Specified
Adding a win condition does not automatically define repetition, move-count or stalemate handling. Preserve the implementation's draw rules.
Three-Check
Three-Check preserves ordinary move legality and checkmate but also wins when a player gives the opponent a third legal check.
Check Counter
Three-Check needs persistent check counts in addition to board occupancy.
Third Check Wins
Under the current Lichess profile, the legal move that gives the opponent the third check wins immediately.
Checkmate Still Wins
The ordinary checkmate objective remains a valid win condition in both current Lichess Three-Check and King of the Hill.
Double Check Counts as One Checking Event — Current Lichess Profile
Lichess explicitly counts a double check as one check event for the Three-Check counter.
Check as Strategic Currency
A check has two values: its normal forcing effect and progress toward the three-check win condition. Sacrificing material for a durable checking sequence can therefore be rational.
Sacrificial Checking
Sacrificial checking is unusually important in Three-Check because a check can be progress toward the win condition even when the checking piece is lost. A sacrifice is justified when the resulting check count or forced sequence leaves the opponent unable to prevent the second/third check; material recovery is secondary to the objective race.
King-Safety Escalation
King safety escalates as the opponent's check count approaches three. After one check, normal development may still dominate; after two, almost every potential checking line becomes a direct losing threat, so prophylaxis, queen exchange and control of checking squares can outweigh ordinary material or positional gains.
Check-Count State in Data
Store checks delivered by each side in the position/game state; PGN moves alone can reconstruct it only if every prior move is available and interpreted under the same rules.
Three-Check Openings / Endgames
Three-Check opening play rewards rapid development and access to checking lines, but reckless early checks can lose tempi and material if they do not lead to a sustainable sequence. Endgames can remain highly tactical because a side with two checks banked may need only one rook or minor-piece check to win, making simplification very different from orthodox chess.
King of the Hill
King of the Hill preserves ordinary FIDE move legality and wins when a player legally moves their king to one of the four central squares.
d4 / d5 / e4 / e5
The current Lichess KOTH winning center consists of d4, d5, e4 and e5.
Legal King Entry Wins
The king must enter the center legally: it cannot move into check merely to claim the hill.
King Remains Royal
In KOTH, the king retains normal royal/check restrictions. This is not a king-capture or non-royal-king game.
Checkmate Still Wins
The ordinary checkmate objective remains a valid win condition in both current Lichess Three-Check and King of the Hill.
Central King Route
The king's route to the center becomes a strategic objective, but premature exposure can still lose by checkmate.
Central Control
Squares controlling the four hill squares become objective-critical even when they would be only positional squares in orthodox chess.
Exchange / Endgame Consequences
In King of the Hill, exchanges can favor the side whose king gains a clearer route to d4/d5/e4/e5, even when ordinary endgame material remains equal. Simplification removes checking pieces and blockers, so king centralization can become decisive much earlier than in orthodox chess; always compare the hill race with checkmate risk before exchanging.
KOTH Practice Set
A strong understanding includes identifying legal hill-entry routes, center-control resources, checkmate-vs-hill races and the evaluation changes created by king centralization.
An Added Objective Changes the Value of Ordinary Moves
Three-Check and King of the Hill are useful examples of a general design principle: you can keep almost all orthodox move rules and still transform strategy by changing the objective.
In Three-Check, a check can be valuable even when it wins no tempo by orthodox standards because it permanently advances the check counter. The first two checks can therefore behave like a resource that changes future king mobility. Sacrifices that would be unsound in ordinary chess may become correct if they force the final checking event.
In King of the Hill, the center becomes a terminal goal for the king. Centralization is no longer merely an endgame principle: a legal king move onto d4, e4, d5 or e5 can end the game immediately under common implementations.
Objective Precedence Must Be Written Down
Whenever several wins coexist, document what happens when a move creates more than one terminal condition. Also specify repetition, stalemate and move-count behavior rather than assuming they inherit automatically. The core rules may be stable while platform details still differ.
State Awareness Matters More Than It First Appears
An orthodox board diagram is not sufficient to evaluate Three-Check because the same arrangement of pieces can have different results when the check counters differ. A position at 2–0 in checks is strategically different from the identical board at 0–0. Analysis records should therefore preserve the counter as part of the position state.
King of the Hill has a different issue: the terminal objective is visible on the board, but the legality of the king route remains orthodox. A king cannot “race through check” merely because the destination is a winning hill square.
Endgames Can Change Character Before Material Does
In Three-Check, simplification does not necessarily reduce danger if one side already has two checks. A nominally safe king may remain one forcing move away from defeat. In King of the Hill, exchanges can increase the importance of central access because fewer pieces remain to deny the four hill squares.
When comparing an orthodox line with a variant line, ask which objective becomes easier after simplification—not just who wins the material exchange.