A fluid type scale is a set of straight lines, and they cross.

h2 is 1.6rem + 1.2vw and h3 is 0.6rem + 2.6vw. Those are two lines with different slopes, so they meet — at 1143px. From 1144px the h3 is larger than the h2, and at 1532px the h3 hits its own maximum and falls back underneath. So the hierarchy is upside down over a band bounded on both sides, and 768px, 1024px and 1920px all pass.

The engine is free and needs no account. Paste the scale — one step per line, largest first. Every clamp has two exact crossover viewports that appear in no declaration: it is pinned at its minimum until (min − A×root) × 100 ÷ B and at its maximum from the same expression on the other bound. The ratio between two fluid steps is not constant — it drifts unless both terms of each step are the same multiple of the one below, which is the only construction that makes it exact and the only one that makes crossing impossible. And a vw term does not answer a reader's font-size setting: page zoom scales vw, but the browser's default-font-size preference scales rem only, so the share of the request a step can answer is exactly the rem term's share of its size. The same is true of the bounds — a clamp spends most of its range pinned against one. Every lane ships a worked example that costs nothing. Writing the report needs credits.