Player 1 picks a word in a modern language and provides the proto form of it (it doesn't necessarily have to be the oldest possible form, for instance, you might trace an English word back to Latin, or you might trace it back further to PIE, you can decide).
Player 2 has to give another modern word in a different language that is a decendant of Player 1's proto word, then chooses another modern word from that language and provides its proto form for Player 3.
Bright < Proto-Germanic - *berhtaz ("bright")
P2: Proto-Germanic - *berhtaz ("bright") >
eldur ("fire") < Proto-Germanic - *ailidaz ("fire")
P3: Proto-Germanic - *ailidaz >
caer ("fort, citadel").
Please give English translations for the modern words (and the ancient ones too, if possible).Note II:
In the event that someone provides a proto word that is not ancestral to any words in any other languages (to be avoided, if possible), the next player should provide another word in the same language as P1 which developed from that word, or failing that, choose another root word from the same language as given proto word, or failing that, just completely start afresh with whatever word in whatever language you like.