sól og bjór

Reykjavík gets sun like other cities get snow days. Rarely, suddenly, and everyone drops what they're doing.

When it happens, the whole city asks the same two questions: where is the sun actually hitting right now, and where is the beer not 1.800 krónur? Downtown Reykjavík is a maze of low buildings that throw long shadows even in June, so a terrace that was glorious at three is in the shade by five. You can be sitting twenty meters from sunshine and not know it.

So I built sologbjor.einargudni.com — a small app that ranks Reykjavík bars by exactly those two things: most sun and cheapest beer, right now.

the sun is a geometry problem

The interesting part is figuring out whether the sun is actually hitting a specific terrace, not just whether it's up.

The sun's position is pure math — SunCalc gives you azimuth and altitude for any coordinate at any moment, accurate to a fraction of a degree. The hard part is what's in the way. For that I pulled building footprints and heights from OpenStreetMap and precomputed a 360° horizon profile for each bar's terrace: for every compass direction, how high does the skyline reach from that exact spot?

Then the runtime check is almost embarrassingly simple. Where is the sun? Is it above the skyline in that direction? That's it. No 3D rendering, no ray casting, no shadow simulation. All the expensive work happens offline in a script; the app ships a static JSON file and does a lookup.

Clouds get a say too. Open-Meteo provides hourly cloud cover for free, with no API key, and Reykjavík conveniently lives on UTC year-round so the timestamps just line up. But I don't apply cloud cover linearly — 50% cloud in Reykjavík still feels sunny, so the attenuation curve is convex and floored at 0.3. A geometric model corrected by lived experience.

the beer is a data problem

There's no API for happy hours. I scraped what I could from visitorsguide.is, which covered about half the bars, and hand-researched the rest — calling on memory, websites, and one very useful thread on X. The result is a static bars.json with 25 bars, each with price data and happy-hour windows.

Happy hours drift, so a GitHub Actions workflow re-scrapes weekly and commits the refreshed data straight to main. The data maintains itself, mostly. There's also a "fix happy hour" button in the app for when it doesn't.

static core, thin edge

My favorite decision in the whole project is what the backend doesn't do.

Everything deterministic — building heights, horizon profiles, bar data — is precomputed and shipped as static files. The frontend is a Vite React SPA that weighs 69 KB gzipped and runs entirely client-side: it knows where the sun is, it knows the skylines, it fetches the weather itself. The only live server code is a single Hono endpoint on Cloudflare Workers that relays feedback to Slack, because that's the one thing that needs a secret.

The first version had more ambition: a crowd layer where people could vote on sun and prices, backed by Turso. I built it, then paused it before launch. Cut to static, ship, see if anyone cares. The code is still there, dormant, waiting for users to deserve it.

the map

There's a shade map, because of course there is. MapLibre GL renders the downtown buildings as 3D extrusions, lit according to the actual sun position, with the shadow union computed via polygon-clipping so overlapping shadows don't double-darken.

The map chunk is four times the size of the rest of the app, so it lazy-loads behind a toggle, and the toggle remembers your choice in localStorage. If you opened the map last time, the chunk preloads quietly while the browser is idle.

Two bugs from this part earned their place in my notes. First: flat polygon fills disappear when 3D extrusions are on the map and the camera is pitched — the depth buffer hides them. The fix is rendering "flat" shapes as extrusions with near-zero height. Second: React's lazy() caches a rejected import forever, so an error boundary around a lazy chunk must offer reload, not retry — retry will re-throw the same cached rejection until the heat death of the universe.

the stack, plainly

• Bun monorepo, TypeScript everywhere