marrow vs Almanac

marrow is a feed of ideas worth keeping. Instead of an endless scroll of noise, you move through short, self-contained explanations (one concept per screen) across computer science, finance, math, and science. Each card explains a single idea in a few sentences: why appending to a dynamic array is O(1) on average, what the Rule of 72 estimates, and dozens more. Some cards ask you a question first. Reveal the answer, then tell marrow how well you knew it. The ones you find hard come back sooner; the ones you already know drift further out. That is spaced repetition, built into the scroll, so the ideas you want to keep actually stick. - One idea per screen, made for short sessions - Four domains: computer science, finance, math, and science - Self-grading with spaced repetition, so reviews return at the right time - Fully offline: no account, no ads, no tracking. Your progress stays on your device. Scroll to learn.

Every day, as the ancients counted it. Almanac names any day from 10,000 BC to AD 3000 the way the Maya, the Egyptians, and the astronomers of China and Islam counted it, and shows when sixteen ancient sites, from Göbekli Tepe to Machu Picchu, line up with the sun, the moon and the stars. TURN THE WHEELS OF TIME • Spin the Maya, Egyptian, Islamic and Chinese calendar wheels with your finger and watch the days go round. • Count the Maya Long Count up and down, and find when any Calendar Round last came round and when it comes next. • Follow the Sothic cycle, as Sirius's rising walks round the Egyptian year over the centuries. • Turn the moon through its month. On the day of a solar eclipse, watch the sun slide in behind the new moon and the sky darken. • Type a date in any calendar, from 13.0.0.0.0 to 1 Thoth or 1 Muharram. WHERE STONE MEETS SKY • Sixteen sites, including Stonehenge, Newgrange, Giza, Karnak, Abu Simbel, Chichén Itzá, Teotihuacan, Angkor Wat and Machu Picchu. • Thirty alignments: solstice sunrises and sunsets, the moon at its standstills, stars rising over the horizon or crossing a shaft. • Watch each alignment happen: drag through the hours and see the sun cross the plan into line. • Plans sit in a compass that turns with your iPhone, under a glass crystal that catches the light as you tilt it. • Visit in time: jump to moments in each site's history and see the sky as it stood then. • Follow a site to get a reminder before its next alignment, and a live countdown on your Lock Screen on the day. THE SKY ABOVE YOU • Your sky: where the sun rises and sets for you, today and at the solstices and equinoxes. • Every solar and lunar eclipse, with what you can see of it from where you are or from any site. • The wandering pole: drag through 27,000 years and watch the pole star change from Vega to Thuban to Polaris. YOUR BIRTHDAY, ANCIENTLY Find your Maya day sign, Egyptian season, Chinese animal, and your Hijri, Hebrew and Indian dates, and share them as a card. WIDGETS • Calendar Wheel: a calendar wheel turned to today, with buttons to step it day by day. • Ancient Site: a site and its next sky event, or shuffle through them all. • Sky Compass: where the sun stands right now over a site's plan. Every calculation follows published astronomy, from Jean Meeus's Astronomical Algorithms to modern precession models, and every alignment shows its source. Almanac works offline, with no account, no ads and no tracking.