Approaches

Risk and survival objectives

Judge a move by its worst outcomes, or by how long the game keeps going, and see whether caution extends life.

Learn the whole spread of how long a game might last, and only leave the safe move when the evidence says so.

Instead of judging a column by its average outcome, judge it partly by its worst outcomes, and find that the resulting policy dies much sooner.

Play normally on a healthy board, then switch to worst-case thinking when height, crowding, or covered discs put the game at risk.

Clear numbered discs and open covered ones fast enough to keep the board from filling.

Ranks columns partly by their worst imagined futures. Every tested risk setting trails the baseline.

Adds one human rule to the depth-4 search by refusing risky drops above a disc's vertical safe zone, then tests whether the rule extends life.

Retunes an existing policy for survival milestones instead of average score while changing nothing else. The result barely moved.