Blacken is a Java library for Roguelike development. It supports arbitrarily resizing the window. It maintains a "preferred size", changing the font size as needed. By default, all applications support Alt-Enter for fullscreen mode. It strives to support Unicode well. A cell contains a sequence of codepoints. Codepoints may be outside the Basic Multilingual Plane or zero-width accents. All key input consists of valid Unicode codepoints. Special keys are handled by codepoints in "private use" planes. Modifier keys are handled through a prefix character (like Unix systems handle Alt via the Escape character).