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+# Migrate from Ethereum
+
+Tangerine's version of EVM is almost the same as the original EVM, therefore Tangerine version of Solidity is almost the same as the original Solidity. If you have built a smart contract on Ethereum, you can usually deploy the exact same contract onto Tangerine without any modification.
+
+However, there are still some minor differences between the Tangerine's version of Solidity and its Ethereum counterpart to look out for, as listed below:
+
+## Gas Limit
+
+In Tangerine, **there is no unspent gas**.
+
+If the actual execution of a transaction costs less gas than the set amount, **you still have to pay for the gas amount you've set**. So please set the gas amount wisely.
+
+The reason for this is that in Tangerine, transaction are not executed at the time they get packed into a block. So the number of transactions that can get into a block depends on the gas amount set in the transactions, not the actual gas amount consumed while executing the transactions.
+
+## On-Chain Random Oracle
+
+This is more of an additional feature than Ethereum's EVM.
+
+Tangerine provides [On-chain Random Oracle](On-Chain-Random-Oracle.md). This means you can get unbiased random seeds in your smart contract easily and at low cost.
+
+Here's a simple Solidity smart contract that utilizes Tangerine's on-chain randomness,
+```
+pragma solidity ^0.5.2;
+
+import "github.com/byzantine-lab/tangerine-random-lib/RandomLib.sol";
+
+contract Hello {
+    uint256 public value;
+
+    event UpdateNumber(uint256 _value);
+
+    function update() public {
+        value = Random.rand();
+        emit UpdateNumber(value);
+    }
+
+    function get() public view returns (uint256) {
+        return value;
+    }
+}
+```
+The `Random.rand()` function call used in the contract gives you the random seed generated from the threshold signature of a group of block producing nodes.