Guns Up! will allow cross-play between 2 platforms

Guns Up!
Release Date: May 19, 2015
Official Website: Link
Supported game modes:
  • Single player
  • Multiplayer
Supported player perspectives:
  • Third person
  • Side view
Crossplay platforms:
Guns Up! will support cross-play across multiple platforms. It will be possible to play together with your friends on Playstation 4 and Windows PC. Please check out all the details on the game's official website!
Cross-Platform Combination Details:
Source: Link
Additional Info: Only PVP/Aliance battles are crossplay.
Summary:
GUNS UP! is a free-to-play side-scrolling strategy game that pits players against each other in a battle to destroy enemy bases to increase their own army’s strength. GUNS UP! combines the fun of enemy base invasion with tower–defense, for an experience like no other on the PS4™ system. •Free-To-Play – Players on PS4 can download and play GUNS UP! for free. Players can use in-game experience or purchases from the store to unlock upgrades to: supplement their armies, customize their characters, and upgrade their bases. •Find and Destroy Enemy Bases – While connected online, players can build their army to obliterate opponents’ bases to become to ultimate field commander •Build And Defend Your Base – Set up and tweak your military stronghold to keep the enemy away from your base •Leveling System – Upgrade bases and enhance your troops by unlocking perks. As you gain experience, your troops and armaments level up, improving players’ abilities to conquer more enemies
Screenshots:
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Supported game modes:
  • Single player
  • Multiplayer
Supported player perspectives:
  • Third person
  • Side view