:root{--bg:#f7f9fc;--card:#fff;--muted:#6b7280;--brand:#0f62fe}*{box-sizing:border-box}body{font-family:Inter,ui-sans-serif,system-ui,-apple-system,Segoe UI,Roboto,Helvetica Neue,Arial;background:var(--bg);margin:0;color:#111}.topbar{background:linear-gradient(90deg,#fff,#f0f4ff);padding:16px 24px;border-bottom:1px solid #e6eef9;display:flex;justify-content:space-between;align-items:center}.topbar h1{margin:0;font-size:18px}.main{display:flex;height:calc(100vh - 120px)}.left{width:360px;border-right:1px solid #e6eef9;padding:16px;overflow:auto}.content{flex:1;padding:18px;overflow:auto}.upload-card,.list-card,.note-card{background:var(--card);padding:12px;border-radius:8px;box-shadow:0 1px 2px #1018280a;margin-bottom:12px}.button{background:var(--brand);color:#fff;padding:8px 12px;border-radius:6px;border:none;cursor:pointer}.small{font-size:13px;color:var(--muted)}.input{width:100%;padding:8px;border-radius:6px;border:1px solid #e6eef9}.empty{padding:24px;background:var(--card);border-radius:8px}.footer{padding:12px 24px;text-align:center;color:var(--muted)}.study-item{padding:8px;border-radius:6px;cursor:pointer}.study-item:hover{background:#f1f6ff}