Harmony is a powerful blockchain that is EVM compatible with sharding and staking features. Developing on Harmony should feel very familiar for Ethereum developers, as Harmony is fully Ethereum compatible and inherits almost all the tools and libraries from Ethereum, like truffle, remix, web3js, etc.
The simplest way to interact with Harmony blockchain is via JSON RPCs.
To really explore the full potential of Harmony blockchain, creating a wallet is the next step.
Harmony CLI, also provides a quick way to create/manage wallet, interact with blockchain, etc.
Several development environments exists: mainnet, testnnet, localnet
Other SDKs include: Golang CLI, Java SDK, Python SDK
Note that, the Python SDK has only read-only features, meaning no transaction signing or smart contracts
talk.harmony.one - for reporting issues, asking questions, or interact with other developers
Harmony dev reddit
Harmony dev telegram
Only cross-shard native token (ONE token) transfers are allowed. No cross-shard for HRC20 or other contracts. Meaning, smart contracts are deployed on shard-0 and all contract interactions happen on shard-0. Contracts can still be deployed on other shards, however they won't be able to interact with contracts in other shards. We have cross-shard smart contract on our roadmap for Q3, 2021.