Byeoldosa vs HistoryLayer

Byeoldosa is an arithmetic practice app for working through addition, subtraction, multiplication, and division step by step. • Levels are organised by difficulty, so you can start from the basics and move on to more advanced problems at your own pace. • Problems range from single-digit to three-digit numbers, with stages that change depending on whether carrying or borrowing is involved. • In vertical (column) calculation mode, you can follow each column one box at a time, much like writing out the sum on paper. • Every practice set is saved automatically, and your scores and time spent are shown in simple charts, so you can see how your speed and accuracy change as you keep practising. It’s a good fit for students who want to strengthen their arithmetic, for anyone who’d like a bit of mental exercise, or for those moments when you just feel like doing a few number problems. Whenever you feel like practising numbers, just open Byeoldosa.

HistoryLayer is a map of the world you move through time. Drag the year along the bottom and the borders change with it — maps running from 123,000 BCE to the present day, through the Upper Palaeolithic, the Bronze Age, classical antiquity, the Middle Ages, the industrial age and the world wars. Stop anywhere and the map fills in with what was happening on that ground: the events of the year, the people alive for it, the wars under way, and the settlements that existed by then. WHAT IS ON THE MAP • More than 23,000 events — warfare, politics, disaster, religion, science, art, exploration and society • More than 12,000 lives, placed where they were lived • More than 800 wars, drawn as the ground they covered rather than as a pin • More than 13,000 settlements, appearing in the year they were founded MOVING THROUGH TIME The ruler carries a stop for every map the atlas holds, and the era rail beside it names where you are. Open the year bar to scrub year by year between two stops, and the map answers with the closest year it has and says which one that is — it never pretends to a map it does not hold. READING A RECORD Tap anything on the map and it opens beside it: the date, what happened, a longer story where one is written, and pictures where they exist. Records that have been checked by hand say so. SHOWING LESS, OR MORE Turn events, people, wars and settlements on and off. Switch between the year's own borders and a detailed map that adds provinces, rivers and roads. Search by name across everything at once. KEEPING WHAT YOU FIND Sign in to save records, write private notes on them, and gather them into collections. Signing in is optional — the whole atlas is open without an account, and an account can be closed from inside the app at any time. WHERE THE MAP COMES FROM Historical borders come from the historical-basemaps project, released under the GPL-3.0. Present-day borders come from Natural Earth. Records are drawn from Wikipedia and Wikidata; where a record has been checked by hand, the app says so rather than leaving you to guess. Light and dark, on iPhone and iPad.