If anyone is having trouble on Expert 35, try to place some Multi Fire Towers inside the first corner (I used 4 and upgraded them to max level) and a Super Tower near the base. I used many level 1 Freeze Tower nears the Multi to keep the damage on the area as high as possible, build some near the Super too. When you get Multi's Maxed and Super with 2 upgrades, send all Waves (to me was around wave 35) and keep bombing (Small Bomb) in the corner of the Multis. Took me really long to figure this tactic out and get Expert on that level. Hope it helps.