Cross-Platform Action Game Development

I'm looking to develop an engaging action mobile game targeting both iOS and Android platforms. The game should be designed with two key features:

1. Multiplayer Mode: The game must support real-time multiplayer functionality, allowing players to compete with or against their friends or other users from around the globe.

2. In-app Purchases: The game should integrate a well-balanced in-app purchase system. This should not disrupt the gameplay but rather enhance the gaming experience, offering players optional upgrades or exclusive items.

Ideal skills for this project include mobile game development, proficiency in both iOS and Android coding languages, and experience in implementing multiplayer functionality and in-app purchase systems. Please provide examples of your previous work in your proposal.