In the affirmative form, we use used to to describe an ongoing action or state in the past. We cannot follow the word to with playing. We need to use the infinitive form after used to: I used to play tennis.
Habitual aspect
Used to vs would: both describe past habits, but used to implies the habit has stopped and works for states (I used to live there). Would describes repeated actions within a known time frame and needs context (Every summer, we would swim). Mixing them up subtly shifts meaning.
The habitual aspect = present simple (current habits), used to (past habits, ended), would (past repeated actions in context).
Diagnostic: is it a past state? → only used to. A past repeated action with a time frame? → either works. Does it imply the habit ended? → used to is clearer.
C1 | Advanced
C1 vs C2: C1 means fluent and flexible use with occasional gaps in very unfamiliar domains. C2 means native-like command of idiom, irony, and register across any subject. If you can handle advanced grammar but still miss cultural nuance or very rare idioms, you're C1.
C1 is the advanced CEFR level: inversion, cleft sentences, subjunctive mood, advanced conditionals, and precise register control in professional and academic contexts.
Diagnostic: can you write persuasively in different registers and catch subtle irony? Consistently → C2. Sometimes → C1.
Hard
Hard vs Medium: Medium tests one rule with realistic distractors. Hard tests interacting rules, edge cases, or context-dependent answers where multiple options seem correct until you think deeply. If you're scoring 80%+ on Medium, try Hard to find your real gaps.
The Hard tag filters for B2+ challenges with layered difficulty: rule interactions, subtle distractors, and contexts that demand genuine grammatical reasoning.
Diagnostic: if Hard questions feel impossible, drop to Medium and master the individual rules first. Hard assumes you already know each rule — it tests whether you can apply them together.