How mortgages really work — and what your bank's calculator doesn't show you
The standard mortgage formula, the three things the bank's calculator never shows, and the honest way to use the numbers.
Read the guide → Health metrics · Definitive guideWhat BMI actually measures — and what to use instead
A population screening tool, not a personal one. The formula, the limits, and the four better metrics in rough order of cost.
Read the guide → Personal finance · Definitive guideWhy compound growth is magic — and why the line goes up, not straight
Exponential growth, the rule of 72, and why the early saver always wins. The math, written out, with the assumptions named.
Read the guide → Security & privacy · Definitive guideHow to choose a strong password — and why your browser already does the hard part
What makes a password weak, what makes it strong, and why your browser's built-in password manager beats the old advice.
Read the guide → Code & data · Definitive guideJSON for people who hate JSON — a practical guide for non-engineers
What JSON is, how to read it, how to spot the errors, and the tools that will format and validate it for you.
Read the guide → Code & data · Definitive guideRegular expressions without the pain — a 5-minute practical guide
The four characters that matter most, the syntax, and a worked example of a real regex from this site.
Read the guide → Design · Definitive guideHow to pick a colour palette that doesn't look like a 2003 Geocities page
Two anchors, one accent, a small set of semantic colours. The art-school waffle removed.
Read the guide → Design · Definitive guideImage file formats explained — when to use PNG, JPEG, WebP, AVIF, or SVG
The wrong format bloats your page or makes the picture look like a 1998 webcam. The modern defaults.
Read the guide → Music & audio · Definitive guideBPM, tempo, and time signature — a 3-minute primer for the rest of us
BPM, tempo, time signature, and the free tools on this site that tap, count, tune, and build chords for you.
Read the guide → Astronomy · Definitive guideHow to read a star chart — and pick a telescope that is not a waste of money
The eyepiece math, the Dawes and Rayleigh limits, and the free tools on this site that will calculate magnification and exit pupil.
Read the guide → Writing & business · Definitive guideHow to write a cover letter, resume, or business email that someone will actually read
The four-part structure, the two phrases that should never appear, and the free tools that will proofread, paraphrase, and tone-check the result.
Read the guide → Wellbeing · Definitive guideHow to breathe, ground, and calm down — three techniques that work in under 5 minutes
Box breathing, 4-7-8 breathing, and the 5-4-3-2-1 grounding technique. The physiology, when to use which, and the free tools that pace you through them.
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