COSESAI

API Contract Stress Tester cover poster — every OpenAPI constraint implies its own negation.

API Contract Stress Tester: Every Constraint Implies Its Own Negation

By xiezixing 2026年7月12日

A boundary-value grammar that walks your OpenAPI document field by field — every documented constraint implies its own negation, and the tool turns that implication graph into a JSON test plan you can replay.

Accessibility Audit Report Generator — Cover Poster

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Accessibility Audit Report Generator: 6 Categories, 4 Severities, 1 Readable PDF

By xiezixing 2026年7月12日

A WCAG audit that ships a PDF a product manager can read in three minutes — 6 categories, 4 severity levels, 3 report sections, 1 shipped artifact.

X.509 Certificate Decoder — read PEM certs in 30 seconds

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X.509 Certificate Decoder: 8 Fields, 4 Traps, 5 Sibling Tools for Reading PEM

By xiezixing 2026年7月12日

Parse PEM certificates into subject, issuer, validity, SANs, fingerprint, and key usage — what openssl x509 prints, rendered without the command line.

GeoJSON to KML converter cover showing coordinate translation workflow

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GeoJSON to KML Converter: The Two Map Formats That Don’t Speak the Same Language

By xiezixing 2026年7月12日

GeoJSON lives in your browser, KML lives in desktop GIS. The translation rules between them are subtle — altitude, ExtendedData, and antimeridian crossings quietly lose fidelity if you get them wrong.

RPE Calculator: Why the 1-10 Scale on Your Last Set Is Harder to Read Than the Number Suggests

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RPE is the Intensity Scale Your Watch Can’t Read

By xiezixing 2026年7月11日

A 1-to-10 number on every working set is the cheapest intensity measurement in training. Here's how to read it, log it, and stack it against heart rate and Training Stress Score.

Video Preview Generator sampled timeline montage

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Before You Watch the Whole File, Generate the 10-Second Version

By xiezixing 2026年7月11日

A practical guide to using Video Preview Generator for evenly sampled timeline triage before committing to a full video review.

Mulch Gravel Soil Bulk Bag Estimator cover showing depth and bulk bag planning

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Mulch Calculator: The Cubic-Yard Mistake That Turns One Bag Into Three

By xiezixing 2026年7月11日

A practical guide to estimating mulch, gravel, topsoil, sand, and compost by depth, density, weight, bulk bags, small bags, allowance, and cost.

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Break-Even Calculator: The Formula Is Simple. The Honesty Is Not.

By xiezixing 2026年7月11日

A break-even calculator does not make the decision. It makes the assumption set visible. Here is how to use one without fooling yourself.

Kepler Orbit Solver — Numerically solve Kepler equation M = E − e·sin E for eccentric anomaly, true anomaly, and orbital radius.

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Kepler Orbit Solver: Why M = E − e·sin E Has No Closed Form (And How to Solve It Anyway)

By xiezixing 2026年7月11日

Three numerical methods for Kepler's transcendental equation: Newton-Raphson, bisection, and fixed-point iteration — compared on Earth, Mercury, and a near-parabolic comet orbit.

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ASS to SRT Converter: the Format Bridge That Fansubs and Broadcasts Both Need

By xiezixing 2026年7月11日

The format gap between ASS and SRT is wide. This single-pass, client-side converter drops styling, preserves timing, and emits clean numbered cues — for fansubs, broadcast masters, and pipelines that need to read both.