Gravity and support: find the actual landing square
An empty square in a winning line may be several moves away from becoming playable. Read the stack below it before treating it as an immediate threat.
LEARNING CENTRE
Four in a Row: read playable threats before building plans
Learn to distinguish a promising-looking line from an immediate win, recognise urgent replies, and verify a forced next-turn tactic. The playable cases compare legal drops and immediate replies; their task is a specific tactical decision, not a prediction of the entire game.
The rules in this version
Two players share a six-row, seven-column board. Orange starts, then Orange and Violet alternate dropping one token into a non-full column. It lands in the lowest empty square. Four or more consecutive tokens of one player horizontally, vertically or diagonally wins. A full board without a winner is a draw. This classic version has no token removal, wrapping or free placement above a gap. Row 1 is the top and row 6 the bottom.
Four decisions to understand
Immediate wins: test the legal drop, then all directions
Before improving a position, check whether a move already ends the game. Inspect horizontal, vertical and both diagonal directions through the newly placed token.
Immediate defence: stop the actual winning reply
If you cannot win now, enumerate the opponent's legal one-move wins. A useful block removes the real reply, not merely a square that looks dangerous.
Forced next-turn wins: test every opposing reply
Two independently playable winning columns are one way to force a win. A stacked threat can work differently: blocking the lower winning square may make another winning square above it playable. The decisive test is what remains after every legal opposing reply.
Two practice collections
Foundations: read the board before moving
Four studies in legal moves and their immediate effects. Make a prediction, test it, and compare the starting-position answer.
Decisions: compare what happens next
Four studies in future consequences. Distinguish a verified finish, a short tactical proof and a useful feature that does not establish a win.
What the evidence establishes
An immediate win can be checked exactly by making a legal drop and inspecting all lines. A forced defensive move or fork claim must also check the opponent's immediate winning replies. A local threat calculation is not a full-game solver or a promise of perfect play. Statements about central control or future shapes are strategic guidance unless a complete response analysis is supplied. The regular game has two local human players, not a computer opponent.
Each technique has two playable starting positions. The collection and print links reuse those same studies, so a lesson, a practice page and a printed sheet do not count as three different puzzles.
DECISION LAB
Blocking the next threat builds the one above it
Investigate a forced loss that has no immediate winning move on the starting board and no two-column fork.
Test your prediction and follow the evidence →