The periodic table of all 118 elements. Press an element and you get its ionization energy, electronegativity, atomic radius, electron shells, melting point and boiling point.
The table is coloured by whichever property you choose. Darker toward the top right, paler toward the bottom left: that gradient is the periodic trend. The shape reaches you before any of the numbers do.
Each topic has its own URL. Move between them from the topic panel at the top right, and open any of those URLs directly to get the same screen.
Every value lives in your browser. Nothing you press is sent anywhere.