Dynamic & On-Chain NFTs
On-Chain SVG NFT — Full Pattern
// SPDX-License-Identifier: MIT
pragma solidity ^0.8.19;
import "@openzeppelin/contracts/token/ERC721/ERC721.sol";
import "@openzeppelin/contracts/utils/Base64.sol";
import "@openzeppelin/contracts/utils/Strings.sol";
contract DynamicAgentNFT is ERC721 {
using Strings for uint256;
struct Agent {
string name;
uint256 elo;
uint8 tier; // 0=Bronze 1=Silver 2=Gold 3=Diamond
uint256 wins;
uint256 losses;
uint256 badges; // Bitmask of earned badge IDs
}
mapping(uint256 => Agent) public agents;
uint256 private _nextId;
address public immutable arena; // Only arena contract can update stats
string[4] private TIER_NAMES = ["Bronze", "Silver", "Gold", "Diamond"];
string[4] private TIER_COLORS = ["CD7F32", "C0C0C0", "FFD700", "B9F2FF"];
string[4] private TIER_EMOJI = ["\xF0\x9F\xA5\x89", "\xF0\x9F\xA5\x88", "\xF0\x9F\x8F\x86", "\xF0\x9F\x92\x8E"];
event AgentEvolved(uint256 indexed tokenId, uint8 newTier);
constructor(address _arena) ERC721("SpartaAgent", "AGENT") {
arena = _arena;
}
function mint(address to, string calldata name) external returns (uint256) {
uint256 id = _nextId++;
agents[id] = Agent(name, 1000, 0, 0, 0, 0);
_mint(to, id);
return id;
}
// Called by arena contract after each challenge
function updateStats(uint256 tokenId, bool won, uint256 eloChange) external {
require(msg.sender == arena, "Only arena");
Agent storage a = agents[tokenId];
if (won) {
a.wins++;
a.elo += eloChange;
} else {
a.losses++;
a.elo = a.elo > eloChange ? a.elo - eloChange : 0;
}
// Check tier upgrade
uint8 newTier = _calculateTier(a.elo);
if (newTier > a.tier) {
a.tier = newTier;
emit AgentEvolved(tokenId, newTier);
}
}
function _calculateTier(uint256 elo) internal pure returns (uint8) {
if (elo >= 2200) return 3; // Diamond
if (elo >= 1800) return 2; // Gold
if (elo >= 1400) return 1; // Silver
return 0; // Bronze
}
// ─── Full on-chain metadata generation ───
function tokenURI(uint256 tokenId) public view override returns (string memory) {
require(_exists(tokenId), "Nonexistent");
Agent memory a = agents[tokenId];
string memory svg = _buildSVG(a, tokenId);
string memory attrs = _buildAttributes(a);
string memory jsonRaw = string(abi.encodePacked(
'{"name":"', a.name, ' #', tokenId.toString(), '",',
'"description":"A Sparta Arena competitor.",',
'"image":"data:image/svg+xml;base64,', Base64.encode(bytes(svg)), '",',
'"attributes":', attrs, '}'
));
return string(abi.encodePacked(
"data:application/json;base64,",
Base64.encode(bytes(jsonRaw))
));
}
function _buildSVG(Agent memory a, uint256 tokenId) internal view returns (string memory) {
string memory bg = TIER_COLORS[a.tier];
string memory tier = TIER_NAMES[a.tier];
string memory emoji = TIER_EMOJI[a.tier];
// Win rate bar width
uint256 totalGames = a.wins + a.losses;
uint256 winPct = totalGames > 0 ? (a.wins * 100 / totalGames) : 50;
uint256 barWidth = winPct * 3; // max 300px
return string(abi.encodePacked(
'<svg xmlns="http://www.w3.org/2000/svg" width="400" height="400">',
// Background gradient
'<defs><linearGradient id="bg" x1="0%" y1="0%" x2="100%" y2="100%">',
'<stop offset="0%" style="stop-color:#', bg, ';stop-opacity:1"/>',
'<stop offset="100%" style="stop-color:#111111;stop-opacity:1"/>',
'</linearGradient></defs>',
'<rect width="400" height="400" fill="url(#bg)" rx="20"/>',
// Agent name
'<text x="200" y="60" text-anchor="middle" fill="white" ',
'font-family="Arial" font-size="22" font-weight="bold">', a.name, '</text>',
// Token ID
'<text x="200" y="90" text-anchor="middle" fill="rgba(255,255,255,0.6)" ',
'font-size="14">#', tokenId.toString(), '</text>',
// ELO (big center number)
'<text x="200" y="200" text-anchor="middle" fill="white" ',
'font-size="72" font-weight="bold">', a.elo.toString(), '</text>',
'<text x="200" y="230" text-anchor="middle" fill="rgba(255,255,255,0.7)" ',
'font-size="16">ELO RATING</text>',
// Tier badge
'<rect x="140" y="250" width="120" height="36" rx="18" fill="rgba(255,255,255,0.2)"/>',
'<text x="200" y="273" text-anchor="middle" fill="white" font-size="16">',
emoji, ' ', tier, '</text>',
// Win rate bar
'<text x="50" y="320" fill="rgba(255,255,255,0.7)" font-size="12">WIN RATE</text>',
'<rect x="50" y="330" width="300" height="8" rx="4" fill="rgba(255,255,255,0.2)"/>',
'<rect x="50" y="330" width="', barWidth.toString(), '" height="8" rx="4" fill="white"/>',
// Stats
'<text x="50" y="370" fill="rgba(255,255,255,0.9)" font-size="13">',
'W: ', a.wins.toString(), '</text>',
'<text x="200" y="370" text-anchor="middle" fill="rgba(255,255,255,0.9)" font-size="13">',
'L: ', a.losses.toString(), '</text>',
'</svg>'
));
}
function _buildAttributes(Agent memory a) internal view returns (string memory) {
return string(abi.encodePacked(
'[',
'{"trait_type":"Tier","value":"', TIER_NAMES[a.tier], '"},',
'{"trait_type":"ELO","display_type":"number","value":', a.elo.toString(), '},',
'{"trait_type":"Wins","display_type":"number","value":', a.wins.toString(), '},',
'{"trait_type":"Losses","display_type":"number","value":', a.losses.toString(), '}',
']'
));
}
}
Soulbound Tokens (ERC-5192)
// ERC-5192: Minimal Soulbound Token
interface IERC5192 {
function locked(uint256 tokenId) external view returns (bool);
event Locked(uint256 tokenId);
event Unlocked(uint256 tokenId); // Not emitted for pure SBTs
}
contract SpartaBadge is ERC721, IERC5192 {
// All tokens are soulbound — cannot be transferred
function locked(uint256) external pure returns (bool) { return true; }
function _beforeTokenTransfer(
address from, address to, uint256 tokenId, uint256 batchSize
) internal override {
// Allow minting (from == 0) but block all transfers
require(from == address(0), "Soulbound: non-transferable");
super._beforeTokenTransfer(from, to, tokenId, batchSize);
}
}
Composable NFTs (ERC-6059)
// Parent NFT owns child NFTs
// Transfer parent → all children move with it
contract ComposableAgent is ERC721 {
// tokenId → array of child NFT references
mapping(uint256 => ChildNFT[]) public childAssets;
struct ChildNFT {
address contractAddress;
uint256 tokenId;
}
// Attach a badge/item to an agent
function attachChild(
uint256 parentId,
address childContract,
uint256 childTokenId
) external {
require(ownerOf(parentId) == msg.sender, "Not owner");
// Transfer child NFT from sender to THIS contract (parent holds children)
IERC721(childContract).transferFrom(msg.sender, address(this), childTokenId);
childAssets[parentId].push(ChildNFT(childContract, childTokenId));
}
// When parent is transferred, children must go with it
function _afterTokenTransfer(address, address to, uint256 tokenId, uint256) internal override {
// Children are held by THIS contract — the new owner controls them via parent
// (Full ERC-6059 implementation tracks owner via parent chain)
}
}
nickgallick