.problem-card{background:var(--glass-bg);-webkit-backdrop-filter:var(--glass-blur);border:1px solid var(--glass-border);border-radius:var(--glass-radius);box-shadow:var(--glass-shadow);cursor:pointer;flex-direction:column;height:100%;padding:1.5rem;transition:all .3s;display:flex;position:relative;overflow:hidden}.problem-card:before{content:"";background:linear-gradient(90deg,#38b2ac 0%,#319795 100%);width:100%;height:4px;position:absolute;top:0;left:0}.problem-card:hover{background:var(--glass-bg-hover);box-shadow:var(--glass-shadow-hover);border-color:var(--glass-border-accent);transform:translateY(-4px)}.problem-card-header{justify-content:space-between;align-items:center;margin-bottom:16px;display:flex}.problem-title{color:#333;margin:0;font-size:1.4rem;font-weight:700;line-height:1.3}.problem-difficulty{color:#fff;text-transform:uppercase;letter-spacing:.5px;border-radius:8px;padding:.4rem .8rem;font-size:.8rem;font-weight:600}.problem-description{color:#666;margin:.8rem 0;font-size:.9rem;line-height:1.5}.problem-tags{flex-wrap:wrap;gap:.4rem;margin:auto 0 1rem;display:flex}.problem-tag{color:#667eea;background:#667eea1a;border:1px solid #667eea33;border-radius:12px;padding:.3rem .7rem;font-size:.75rem;font-weight:500}.problem-meta{border-top:1px solid var(--glass-border);color:#888;justify-content:space-between;align-items:center;margin-top:1rem;padding-top:1rem;font-size:.8rem;display:flex}.problem-approaches,.problem-category{align-items:center;gap:5px;display:flex}.problem-title{align-items:center;display:flex}[data-theme=dark] .problem-card{color:#fff;background:#2d2d44}[data-theme=dark] .problem-title{color:#fff}[data-theme=dark] .problem-description{color:#aaa}[data-theme=dark] .problem-tag{color:#ddd;background:#3d3d54}[data-theme=dark] .problem-meta{color:#aaa;border-top-color:#3d3d54}@media (max-width:768px){.problem-card{padding:1rem}.problem-title{font-size:1.2rem}}