.upgrade-subtabs { display: flex; gap: var(--gap-sm); margin-bottom: var(--gap-xl); border-bottom: 2px solid rgba(255,255,255,0.05); padding-bottom: var(--gap-sm); }
.subtab-btn { background: none; border: none; color: var(--text-secondary); padding: var(--gap-sm) var(--gap-md); cursor: pointer; font-weight: 700; font-size: 1rem; transition: var(--transition-fast); border-radius: var(--radius-md); }
.subtab-btn:hover { color: var(--text-primary); background: rgba(255,255,255,0.05); }
.subtab-btn.active { color: #000; background: var(--essence-cyan); box-shadow: 0 0 15px var(--essence-glow); }

.upgrade-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: var(--gap-lg); }

.upgrade-card {
  background: linear-gradient(145deg, var(--bg-card), rgba(10,10,20,0.8));
  border: 1px solid var(--border-subtle);
  border-radius: var(--radius-md);
  padding: var(--gap-lg);
  transition: var(--transition-normal);
  cursor: pointer;
  display: flex;
  flex-direction: column;
  position: relative;
  overflow: hidden;
  box-shadow: 0 8px 20px rgba(0,0,0,0.3);
}
.upgrade-card::before { content: ''; position: absolute; top: 0; left: 0; width: 100%; height: 4px; background: var(--essence-cyan); opacity: 0.5; transition: var(--transition-fast); }

.upgrade-card:hover:not(.purchased):not(.unaffordable) {
  background: var(--bg-card-hover);
  border-color: rgba(0, 229, 255, 0.4);
  transform: translateY(-8px) scale(1.02);
  box-shadow: 0 15px 30px rgba(0, 229, 255, 0.15);
}
.upgrade-card:hover:not(.purchased):not(.unaffordable)::before { opacity: 1; box-shadow: 0 0 15px var(--essence-cyan); }

.upgrade-name { font-family: var(--font-display); font-weight: 800; font-size: 1.1rem; color: #fff; margin-bottom: 6px; }
.upgrade-cost { font-family: var(--font-mono); font-size: 0.95rem; color: var(--essence-cyan); margin-bottom: var(--gap-md); font-weight: 700; background: rgba(0,229,255,0.1); padding: 4px 8px; border-radius: 4px; display: inline-block; width: fit-content; }
.upgrade-desc { font-size: 0.9rem; color: var(--text-secondary); line-height: 1.5; flex: 1; }

.upgrade-card.unaffordable .upgrade-cost { color: var(--danger-red); background: rgba(255, 23, 68, 0.1); }
.upgrade-card.unaffordable::before { background: var(--danger-red); }

.upgrade-card.purchased { opacity: 0.5; filter: grayscale(0.8); cursor: default; border-color: var(--success-green); }
.upgrade-card.purchased::before { background: var(--success-green); opacity: 1; }
.upgrade-card.purchased::after { content: "✓"; position: absolute; top: var(--gap-md); right: var(--gap-md); color: var(--success-green); font-weight: 900; font-size: 1.5rem; text-shadow: 0 0 10px var(--success-green); }
.upgrade-card.locked { display: none; }