  In recent years, the XLogoOnline programming platform has gained popularity
among novice learners. It integrates the Logo programming language with visual
programming, providing a visual interface for learning computing concepts.
However, XLogoOnline offers only a limited set of tasks, which are inadequate
for learners to master the computing concepts that require sufficient practice.
To address this, we introduce XLogoSyn, a novel technique for synthesizing
high-quality tasks for varying difficulty levels. Given a reference task,
XLogoSyn can generate practice tasks at varying difficulty levels that cater to
the varied needs and abilities of different learners. XLogoSyn achieves this by
combining symbolic execution and constraint satisfaction techniques. Our expert
study demonstrates the effectiveness of XLogoSyn. We have also deployed
synthesized practice tasks into XLogoOnline, highlighting the educational
benefits of these synthesized practice tasks.
