First, you will play as Nina. Go to the right or left until you reach some keys. Use the arm expand to reach the keys. When you are near the upper key, point to the left platform then jump and hold Up and press Circle. Do the same thing at the other two sides. You will now switch to Cortex. Just shoot rapidly at the aiming locations of the big robot. You will also finally understand why Crash ran away. You will now use Crash, using Mecha Bandicoot. Avoid the beams of the Twins. Hold and release A while aiming at the Twins. Repeat this a few times to defeat the Evil Twins.