The problem PayD-Offline Payment Transaction App solves

Limited access to reliable digital payment processing in regions with poor network connectivity poses challenges for individuals and businesses.
Inconvenient, time-consuming, and unsafe traditional payment methods are often the only alternative in these situations.
Digital payments are increasingly becoming the preferred mode of transaction globally, making the need for a reliable offline payment processing infrastructure more urgent.
An efficient and secure offline payment processing system utilizing advanced technologies such as QR codes, NFC, Bluetooth, and Wi-Fi would address these challenges.
The implementation of such a system would enhance financial inclusion and enable seamless transactions even in areas with limited network connectivity.

Challenges we ran into

We ran into the biggest challenge of not having good documentation and resources for wifi p2p connection establishment and also web3j which uses a java wrapper class to interact with a smart contract.
Implementing blockchain using Java is the weirdest yet coolest thing that we did.
We also deployed the contract on the polygon-Mumbai testnet and connected the RPC from Android to the blockchain.