Once the page is loaded, all calculations and renderings happen only in the browser, it generates absolutely NO network traffic.
Guaranteed 0% external libraries (100% pure organic HTML5/CSS3/ES6), no GMO.

ES6 Celestial Computer test, with WebComponents

Position on Earth
Latitude:   Longitude:   
UTC Date, and options
Enter UTC date and time, then click the Compute button.
at : : UTC
Skip planets calculations Skip stars calculations Console Verbose
    Real Time
Transparent Grid Sun Moon Sunlight Moonlight Wandering bodies Stars Tropics
Globe Mercator Square