This paper presents an integrated interactive user interface for teaching grammatical analysis on the Internet (Visual Interactive Syntax Learning), developed at the University of Southern Denmark, offering a unified system of analysis for 22 different languages, 7 of which are supported by live grammatical analysis of running text. For reasons of robustness, efficiency and correctness, the system's internal tools are based on the Constraint Grammar Formalism (Karlsson 1990), but users are free to choose from a variety of notional filters, supporting different descriptional paradigms, with a current teaching focus on syntactic tree structures, language independent grammatical categories and the form-function dichotomy. VISL's core NLP-programs use hybrid multi-level parsers (Bick 2003), while graphical teaching applications and corpus searching tools are implemented as platform independent Java-programs and Perlegi's. Though lexica and parsing rules are developed individually for each language, a common CG and treebank data format facilitates source data transfer into grammar teaching games, structural or color based visualisation, and linguistic revision of corpus data