Level 4 is surprising easy if you choose to "camp" those spider tanks.
Move your mortar on the hill at the bottom of the map, then just let those spiders coming to you.With a +1 range bonus your mortar can kill those spiders one by one before they can reach you.
After the AI depleted their resources, advance your tanks while being covered by mortar and rocket. Finally, advance mortar and rocket and destroy that main tank and spider.
I destroyed 4x spiders in that mission at hard.
Winning Sinjid needs a lot of LUCK.
When he use the famous Shadow Blend, stun him became VERY difficult. Further more, he CAN use recharge focus in this stage, then 1-shot you to death, This SB combo is nearly invincible. (Just like Sonny 2 Bio's SB combo.)
Although Amber too has SB, but she won't use Master Strike every time, which otherwise wastes SB's speed bonus.
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