Guess the number. Close counts.
Ten questions a round from a pack of 100, with 1,000 points to play for. Clearing a pack opens the next.
Gaps are measured from the smaller number, so a guess of 80 for an answer of 100 is 25% out, and half the answer scores the same as double it.
The scale is logarithmic: each big mark is ten times the last, and every question gets its own stretch of it.