Building an Ethereum Tennis Manager Game: Smart Contract Development

The project builds directly upon foundations laid in a previous development phase, which established the core ERC721 token standard for representing unique digital tennis players. The author has since refined the initial smart contracts, adding critical functionality and improving code structure. Key updates include the integration of events within the TrainableTennisPlayer contract to emit notifications when players train or rest, providing transparent on-chain records of player development.

Furthermore, utility functions have been logically refactored, moved from the TrainableTennisPlayer contract to a more foundational TennisPlayerBase contract. This architectural decision enhances code modularity and maintainability. At this stage, the game’s core loop is functional: owners can mint new player NFTs and strategically increase their player’s attributes and condition through the training and resting mechanics encoded in the smart contracts, directly influencing their competitive potential.

A central challenge in translating a simulation game to the Ethereum blockchain is managing the economics of computation. Inspired by web-based manager games, the developer initially considered automated daily match simulations. However, this model would require the system itself to pay escalating gas fees—a potentially unsustainable cost as the player base grows. The proposed solution shifts this economic burden to the participants.

In the current design, matches are player-initiated transactions. An attacker (the challenger) submits a transaction, forwarding the gas cost for the match simulation. The winner is algorithmically calculated and recorded as soon as the block containing the transaction is confirmed. This model aligns incentives and ensures the game’s operational costs are directly tied to user activity. Crucially, matches consume a player’s ‘condition’ resource, requiring periods of rest managed via the TrainableTennisPlayer contract, adding a layer of strategic resource management.

To prevent predatory gameplay where high-level players could repeatedly target and drain the condition of weaker opponents, the developer has implemented a registration-based system. Players must actively ‘enlist’ to become eligible for challenges. They can be delisted manually by their owner or automatically by the smart contract if their condition falls below a minimum threshold after a match. This mechanism creates a protected competitive pool and encourages strategic management of player readiness.

The game’s logic is distributed across a clear contract architecture. The TennisPlayerBase contract serves as the foundational layer, housing core data and utilities. The TrainableTennisPlayer contract inherits from this base to handle the training and resting mechanics. The newly introduced CompetingTennisPlayer contract contains the match logic, including the public functions for enlist(), delist(), and playMatch().

The playMatch() function enforces the game’s rules: both players must be enlisted, the caller must own the attacking player, and both must have sufficient condition. After resolving a simple stat-based comparison (with more complex mechanics planned for later), the contract automatically delists players who are no longer in match condition. The author notes that this contract requires thorough unit testing, which is the immediate next step in the development cycle.

Looking ahead, the project remains in active development. Following rigorous testing, the next phase involves building an additional, yet-to-be-named contract that will act as the main entry point and game manager. The final technical layer will be a user-friendly frontend built with React and Redux, allowing users to interact with their NFT players and the game’s mechanics directly from a browser. The entire codebase is open-source and hosted on GitHub, inviting collaboration from other developers in the blockchain and gaming communities.