Added battle record leaderboard
According to the player's record, given the corresponding military rank, and reward additional attribute points
Added mech evolution technology tree
Four basic mechs, three stages of evolution
Add three special skills that consume X coins
Experienced - (Passive Skill) Death will not lose experience.
Diligent Pursuit - (Active Skill) In a period of time, the experience gained doubled.
Cold Snap X - (Active Skill) Freeze the machine immediately and reset the cooldown of all skills.
Unlock condition of mission level bug has been fixed