built an orderbook simulator you can read about bids/asks all day, but until you watch a fat market order walk the book and destroy your pnl through slippage, it doesn't click if you're touching perps (or trying to understand Hyperliquid or Lighter) you need to internalize this here's what actually happens when you trade. look at the order book above - every order sits in a queue. bids (green) = buyers waiting. asks (red) = sellers waiting. that yellow line in the middle is that's the "price" - really just the midpoint between best bid/ask spread = best ask - best bid. tighter spread = more liquid market = better fills limit orders add liquidity. i'll place a 0.5 BTC buy at $99k. updated book: see how it just sits there in the book? that's making. you're providing liquidity for others to take maker fees are lower because exchanges want thick books. more liquidity = more volume = more fees market orders are violent. watch this 5 BTC market buy - it doesn't get one price: it eats through $101k, $102k, $103k... your "$100k buy" becomes $101.5k average fill see that volume distribution bar at the bottom? 81% bids vs 19% asks. when this tilts hard one way, market's about to move (unless there's phantom / pvp flow) you can upload your own trade sequences via json to see how different strategies and trades affect the book. if there's interest i'll add perps specific features: funding rates, margin requirements, liquidation modeling. want to show how a single whale liquidation can cascade through an entire book most people lose money on perps because they don't understand the game they're playing. you're not trading against "the market" - you're trading against other participants who can see everything thing you're doing. ...