Kongzilla
What Flopzilla does, and why range analysis works
Flopzilla is the program that taught a generation of players to stop thinking about their own two cards and start thinking about distributions. This page explains what that kind of tool actually computes, so the numbers mean something when you read them.
A range, not a hand
There are 1,326 two-card combinations in Hold'em, which collapse to 169 classes once you ignore which suit is which: 13 pocket pairs, 78 suited hands, 78 offsuit hands. A range is a weight on each of those combinations — usually 1 or 0, but a solver will play a hand half the time, so fractional weights matter.
That is the matrix you see in every one of these tools: 13 by 13, pairs down the diagonal, suited above it, offsuit below.
What a board does to a range
Deal three cards and every combination in the range becomes something specific. The analyser walks the range and sorts each combination onto a ladder — straight flush, quads, full house, flush, straight, set, trips, two pair, overpair, top pair, and so on down to no made hand — and separately onto a list of draws: flushdraw, open-ended straight draw, gutshot, backdoor flushdraw, overcards.
A hand can be on both lists at once, which is the point. Ace-high with the nut flushdraw is nothing at showdown and a favourite by the river.
Reading the numbers
Two questions are worth asking of every board. How often does this range have it? — if a range makes top pair or better 35% of the time, betting into it every street is a different proposition than if it does so 12% of the time. And what does it do with the rest? — a range with no made hand 40% of the time but a draw in half of those has far more to continue with than the raw number suggests.
Filters: the part that separates a range analyser from an equity calculator
An equity calculator tells you how one range does against another. A range analyser lets you say this is the part of the range that keeps going — top pair and better, plus the flushdraws — and then answers every other question about that subset instead. That is how you model a street: your opponent's range on the turn is not their flop range, it is whatever part of it called.
Class-based filters are re-read every street: a hand marked as continuing because it was a flushdraw stops matching once the draw bricks. That is why Kongzilla also offers a cut by equity, which freezes the combinations it chose so they carry to the next card the way a real continuing range does.
Board texture
There are 22,100 distinct flops. They are not interchangeable: roughly 55% come two-tone, 5% monotone, and about a fifth are ace-high. Working out how a range performs averaged over all of them tells you something no single flop can.