HT Letterspacer is a tool for spacing fonts. Is based on the amount of white space in a glyph box and the usage of 3 parameters to measure it. Using this tool type designers can make their own experiments based on the proportion of letters, general look and others factors to achieve different results and find their own way to use it for different purposes.
Space Bar gives you a lot more insight into the space of your fonts, specially when you are working on a font with multiple masters. It shows you the defined instances of your font and they are represented by curves. So you can work on one master but controlling somehow the other master values and the general project.Space Bar makes information visible, is a visualization tool.
“Speed Punk is a learning tool. It teaches you to better understand the nature of Bézier curves and their curvature, the technical basis of digital type design.” Speed Punk shows the user in a really visual way, how the curve works and its behavior when you play with the handlers, so you can see easily problems and discontinuous curves if graphic shows a jump. Now you can check how smooth are your curves.