When playing Puzzle Strike online, my friends and I encountered a sort of "Sudden Death" mode that activated after many turns of a particularly slow game, resulting in 2-Gems being anted each turn instead of 1-Gems. We could not figure out exactly what the trigger of this was - likely some specific number of turns - or whether or not this rule was supposed to be used in the physical version. I do not believe the rule exists in the Version 1 Rulebook. What is the trigger of this Sudden Death mode that increases the ante, and is it universal to all versions of the game?
The online version uses the 3rd edition rules which state
In a 2-player game, the ﬁrst moment there are two simultaneously empty stacks in the bank, Panic Time is activated and everyone must ante 2-gems from then on. Even if chips later return to bank and ﬁll up some stacks, the game does not return to Normal Time. The ﬁrst moment there are three simultaneously empty bank stacks, Danger Time is activated and everyone antes 3- gems from then on. The ﬁrst time four stacks are simultaneously empty, Deadly Time is activated and everyone must ante 4-gems from then on. Note that if you would ever ante a certain kind of gem that the bank is out of, you must ante it anyway with a stand-in gem of some sort.
For games with 3 or 4 players, the same sort of thing happens. The number of empty stacks needed to activate Panic Time is actually X, where X is the number of players. X+1, and X+2 empty stacks are when Danger Time and Deadly Time activate. The 2 vs. 2 Team Battle mode counts as 4-player game for purposes of the Panic Time rules.