Trace paths through touching letters to spell words, each find drains those tiles, the board collapses and refills, and you race a shrinking grid against the clock.
A 4x4 grid is filled with letters. Drag through, or tap in sequence, a chain of neighbouring tiles to spell a word of three or more letters, then submit it. Every valid word removes its tiles from the board, the survivors fall and the gaps refill from a finite pool. Once that pool runs dry the gaps stay empty, so the grid you are hunting through keeps shrinking. Score as much as you can before time runs out.
Tracing a word through a chain of neighbouring letter tiles is Boggle, introduced in 1973, invented by Allan Turoff and originally distributed by Parker Brothers.
The original addition is that the board is consumed. A found word removes its tiles, the survivors fall, and the gaps refill from a pool that eventually runs dry — so the grid shrinks as you play.
That collapse is borrowed from the match-three puzzle rather than from any word game, and it fixes Boggle's one dull property. A Boggle grid is fixed for the whole round, so a board you cannot read stays unreadable; here every word you find rewrites the board you are searching.
Letterstorm is an original word-tracing and word-search game with a collapsing, draining board that no other grid game plays quite like. It is free in the browser with timed and zen modes and a daily challenge, no download or sign-up needed.