19 posts.
Almost everyone optimises the wrong thing. Measure with cProfile and timeit instead, learn to read the output, and use the two facts that explain most slow Python: membership tests that are O(n) inside a loop, and Amdahl's law, which caps how much any one fix can buy you.
A tincture is an alcohol extract, and two numbers decide whether it works: the herb-to-solvent ratio and the alcohol strength. How to choose both, how to dilute strong spirits to the strength you want, and a calculator that does the arithmetic.
A microwave oven fills its box with a pattern of standing waves, and the hot spots are exactly half a wavelength apart. Melt chocolate in short bursts, measure the spacing, multiply by the oven's frequency, and you have the speed of light to within a few percent.
Boiling, chlorine and filters do three different jobs, and picking the wrong one can leave you sick. The doses, the contact times, the pathogen that only boiling or a cyst-rated filter removes, and a calculator for both the bleach and the amount to store.
Add up what you actually need to keep running, convert it to watt-hours, then pick a battery and a panel that match. Loads with real numbers, an interactive sizing calculator, and the four things that make an outage plan fail.
An old truck brake drum, some black-iron pipe and a hair dryer make a coal or charcoal forge hot enough to shape steel. Build steps, the heat-color chart, and the safety rules blacksmiths learned the hard way.
What actually goes in a bug-out bag, organised by the rule of threes: shelter, water, fire, food, first aid, light, communication and documents. Includes an interactive packing list that totals your bag's weight.
With a fish tank, 99% isopropyl alcohol, felt and a slab of dry ice you can watch muons from space streak through your garage. Parts list, build steps, and how to tell the tracks apart.
Gutter to barrel to tap: size your system with a calculator, add a first-flush diverter and screens, and learn which filtration stages make rainwater fit for the garden, for washing, and (with the right treatment) for drinking.
Divide 72 by the interest rate and you get the years it takes money (or debt, or inflation) to double. Why it works, when it's off, and an interactive calculator that compares the shortcut to the exact answer.
A prioritised one-hour checklist: secure your email first, switch on passkeys or an authenticator app, fix reused passwords, save recovery codes, and freeze your credit. Tick items off as you go.
Length beats complexity. How to build a random passphrase you can remember, why 'P@ssw0rd1!' is weak, what current NIST guidance says, and a calculator that shows how long each password would take to crack.
Three field methods: the stick trick, the shadow method, and the trigonometry of a phone clinometer. Each needs only a tape measure, and there's an interactive calculator to check your numbers.
Binary is just place value with twos instead of tens. Learn to convert binary to decimal and back in your head, then flip the bits yourself in an interactive 8-bit converter.
Strip heavy rust off tools, parts and cast iron with a plastic tub, washing soda, scrap steel and a battery charger. Step-by-step setup, the polarity that matters, and the safety rules.
Pick the right grit, hold a consistent angle, raise a burr, and finish it off. Includes a calculator that turns any sharpening angle into how high to lift the spine of your particular knife.
A short, safe Python script that batch-renames files (photos, invoices, downloads) with a dry run first, so you see every change before it happens. Copy-paste code and an interactive previewer.
The seven red flags that give away most phishing emails, what to do when you're not sure, and a hands-on quiz: click the suspicious parts of a realistic fake email and see how many you catch.
Regular expressions look like line noise until you learn about a dozen symbols. The essentials, five patterns you'll actually use, and a live tester to experiment with in your browser.