Axis-Praxis is a tool for playing with Variable Fonts in the browser. It’s a simple typesetting environment where you can choose fonts, adjust sliders, and press buttons for Named Instances to obtain precise settings on the variations axes built into the fonts. You can also click the axis buttons for an animation along the entire axis. When you begin you will find, pre-installed in the font menu, the four variable fonts built into macOS Sierra. At any point you can play with your own fonts by just dragging & dropping the TTF file onto the page.