Rigid-Body Puzzle Physics

Objects carry properties the player can learn. Weight decides whether a crate holds a seesaw down, density decides what floats, friction decides whether a ramp works, and the same rules apply in every room. Puzzles are then authored as situations rather than as locks: a designer arranges materials and a goal, and any arrangement of forces that reaches the goal counts as a legitimate solution.

Valve released Half-Life 2 in 2004 with a licensed physics engine wired into level design instead of into decoration. Its early chapters work as a tutorial in the rules, teaching buoyancy with barrels and leverage with planks before asking players to combine them. Processing cost had fallen far enough by then to run consistent rigid-body simulation alongside a shooter, which is why 2004 rather than 1998 is the hinge here.

Physics as a solution space made worlds feel governed by law rather than by script, and gave designers puzzles that tolerate improvisation. Reliability is the recurring difficulty: simulations drift, objects clip through geometry, and a puzzle with many valid answers also has many failure states in which the crate you needed has bounced somewhere unreachable. Most games manage that risk by bolting crucial objects into fixed positions.