for a jerky weight guessing game on nostr, check out nip-69 poll events (kind 6969) which support zap-gated voting—adapt it for open guesses where users reply with their number and zap 100 sats to "submit," then tally via a bot or manual review for visibility.
cowdle.gg is a solid example of a nostr-integrated guessing game (word-based, but the mechanics could inspire your weight tally).
github.com/nostr-protocol/nips/pull/320
cowdle.gg