I like it, in that it makes percentiles consistently "roll high", and the two parties merely compare totals to find the victor. My only reservation is that adding two two-digit numbers does require a little more thought than adding one-digit numbers or numbers in the 1-20 range; the time does add up, especially if players are arithmetically challenged.

One solution is to raise skills in increments of 5, and/or express weapon and armor bases similarly. On the other hand, if the tens places are far apart, a simple comparison might suffice. I guess it depends on whether skills and bases are typically in the twenties or the seventies.

(As a counterexample, RuneQuest and its descendants roll under a skill percentile; a fraction of that skill a "critical" or "special" success, and 95-00 counting as a "fumble". If attacker and defender succeed to the same degree, some variants resolve the tie with the **highest** die roll, so as not to penalize highly skilled characters. GURPS, using 3d6, is consistently roll low, but to resolve ties you have to subtract your roll from your skill level, with the greatest **margin of success** being the victor. Subtractions require more thought than addition, which requires more thought than comparing two numbers.)

The probability distribution will be pyramidal (specifically, 2d100 - 101 +/- differences in skills and bases, if I'm not mistaken), which is another advantage of opposed rolls: extreme results are relatively rare.

"On two occasions I have been asked [by members of Parliament], 'Pray, Mr. Babbage, if you put into the machine wrong figures, will the right answers come out?' I am not able rightly to apprehend the kind of confusion of ideas that could provoke such a question."

- Charles Babbage (1791 - 1871)

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