diff --git a/.gas-snapshot b/.gas-snapshot
index 1e54ee4..14862d8 100644
--- a/.gas-snapshot
+++ b/.gas-snapshot
@@ -1,10 +1,10 @@
-DN404Test:testBurnOnTransfer(uint32,address,address) (runs: 256, μ: 277323, ~: 279111)
-DN404Test:testInitialize(uint32,address) (runs: 256, μ: 97313, ~: 112344)
-DN404Test:testMintOnTransfer(uint32,address,address) (runs: 256, μ: 254835, ~: 256235)
-DN404Test:testNameAndSymbol(string,string) (runs: 256, μ: 206378, ~: 206719)
-DN404Test:testRegisterAndResolveAlias(address,address) (runs: 256, μ: 120543, ~: 120621)
+DN404Test:testBurnOnTransfer(uint32,address,address) (runs: 256, μ: 277814, ~: 279525)
+DN404Test:testInitialize(uint32,address) (runs: 256, μ: 98557, ~: 112410)
+DN404Test:testMintOnTransfer(uint32,address,address) (runs: 256, μ: 255465, ~: 256709)
+DN404Test:testNameAndSymbol(string,string) (runs: 256, μ: 206444, ~: 206785)
+DN404Test:testRegisterAndResolveAlias(address,address) (runs: 256, μ: 120621, ~: 120621)
 DN404Test:testSetAndGetOperatorApprovals(address,address,bool) (runs: 256, μ: 129145, ~: 120210)
-DN404Test:testTokenURI(string,uint256) (runs: 256, μ: 157275, ~: 134976)
-DN404Test:test__codesize() (gas: 20274)
+DN404Test:testTokenURI(string,uint256) (runs: 256, μ: 157297, ~: 134998)
+DN404Test:test__codesize() (gas: 20772)
 SoladyTest:test__codesize() (gas: 1075)
 TestPlus:test__codesize() (gas: 398)
\ No newline at end of file
diff --git a/src/DN404.sol b/src/DN404.sol
index 26354a1..a1a2884 100644
--- a/src/DN404.sol
+++ b/src/DN404.sol
@@ -139,6 +139,10 @@ abstract contract DN404 {
         return true;
     }
 
+    function transfer(address to, uint256 amount) public virtual returns (bool) {
+        return _transfer(msg.sender, to, amount);
+    }
+
     function transferFrom(address from, address to, uint256 amount) external virtual {
         DN404Storage storage $ = _getDN404Storage();
 
@@ -234,10 +238,6 @@ abstract contract DN404 {
         return addressAlias;
     }
 
-    function transfer(address to, uint256 amount) public virtual returns (bool) {
-        return _transfer(msg.sender, to, amount);
-    }
-
     function _transfer(address from, address to, uint256 amount) internal returns (bool) {
         if (to == address(0)) revert TransferToZeroAddress();
 
@@ -322,6 +322,25 @@ abstract contract DN404 {
         }
     }
 
+    function _ownerAt(uint256 id) internal view virtual returns (address result) {
+        DN404Storage storage $ = _getDN404Storage();
+        result = $.aliasToAddress[$.ownerships.get(id)];
+    }
+
+    function _ownerOf(uint256 id) internal view virtual returns (address result) {
+        if (!_exists(id)) revert TokenDoesNotExist();
+        result = _ownerAt(id);
+    }
+
+    function _exists(uint256 id) internal view virtual returns (bool result) {
+        result = _ownerAt(id) != address(0);
+    }
+
+    function _getApproved(uint256 id) internal view returns (address result) {
+        if (!_exists(id)) revert TokenDoesNotExist();
+        result = _getDN404Storage().tokenApprovals[id];
+    }
+
     function sisterERC721() public view returns (address sister) {
         return _getDN404Storage().sisterERC721;
     }
@@ -379,12 +398,10 @@ abstract contract DN404 {
             if (msg.data.length < 0x24) revert();
 
             uint256 id = _calldataload(0x04);
-            address owner = $.aliasToAddress[$.ownerships.get(id)];
-            if (owner == address(0)) revert TokenDoesNotExist();
 
-            _return(uint160(owner));
+            _return(uint160(_ownerOf(id)));
         }
-        // `_transferFromNFT(address,address,uint256,address)`.
+        // `transferFromNFT(address,address,uint256,address)`.
         if (fnSelector == 0xe5eb36c8) {
             if (msg.sender != $.sisterERC721) revert Unauthorized();
             if (msg.data.length < 0x84) revert();
@@ -426,10 +443,8 @@ abstract contract DN404 {
             if (msg.data.length < 0x24) revert();
 
             uint256 id = _calldataload(0x04);
-            address owner = $.aliasToAddress[$.ownerships.get(id)];
-            if (owner == address(0)) revert TokenDoesNotExist();
 
-            _return(uint160($.tokenApprovals[id]));
+            _return(uint160(_getApproved(id)));
         }
         // `implementsDN404()`.
         if (fnSelector == 0xb7a94eb8) {
diff --git a/src/DN404NonFungibleShadow.sol b/src/DN404NonFungibleShadow.sol
index 47fc0a3..4c0248e 100644
--- a/src/DN404NonFungibleShadow.sol
+++ b/src/DN404NonFungibleShadow.sol
@@ -282,6 +282,22 @@ contract DN404NonFungibleShadow {
         if (_hasCode(to)) _checkOnERC721Received(from, to, id, data);
     }
 
+    /// @dev Returns true if this contract implements the interface defined by
+    /// `interfaceId`. See the corresponding
+    /// [EIP section](https://eips.ethereum.org/EIPS/eip-165#how-interfaces-are-identified)
+    /// to learn more about how these ids are created.
+    ///
+    /// This function call must use less than 30000 gas.
+    function supportsInterface(bytes4 interfaceId) public view virtual returns (bool) {
+        // The interface IDs are constants representing the first 4 bytes
+        // of the XOR of all function selectors in the interface.
+        // See: [ERC165](https://eips.ethereum.org/EIPS/eip-165)
+        // (e.g. `bytes4(i.functionA.selector ^ i.functionB.selector ^ ...)`)
+        return interfaceId == 0x01ffc9a7 // ERC165 interface ID for ERC165.
+            || interfaceId == 0x80ac58cd // ERC165 interface ID for ERC721.
+            || interfaceId == 0x5b5e139f; // ERC165 interface ID for ERC721Metadata.
+    }
+
     /// @dev Returns if `a` has bytecode of non-zero length.
     function _hasCode(address a) private view returns (bool result) {
         /// @solidity memory-safe-assembly