def interval_vector_from_hits(pattern: str):
    hits = [i for i, ch in enumerate(pattern) if ch == "x"]
    if len(hits) < 2:
        return []
    return [hits[i+1] - hits[i] for i in range(len(hits)-1)]

def groove_analysis(pattern: str):
    vec = interval_vector_from_hits(pattern)
    return {
        "pattern": pattern,
        "interval_vector": vec,
        "complexity_score": len(set(vec)) if vec else 0
    }