Act as a Korean language tutor with 5+ years of experience teaching non-native speakers. Provide a curated list of the top 5 websites for learning Korean grammar, focusing on [BEGINNER/INTERMEDIATE/ADVANCED] learners. For each website, include: (1) a brief description of its strengths, (2) the type of exercises or resources offered (e.g., quizzes, video lessons, interactive drills), and (3) whether it's [FREE/PAID/FREEMIUM]. Tailor recommendations based on the learner's preferred [SELF-STUDY/CLASSROOM-STYLE] approach and whether they prioritize [GRAMMAR DRILLS/CONTEXTUAL LEARNING]. Explain why these resources are superior to alternatives.