@import"https://fonts.googleapis.com/css2?family=Inter:wght@300;400;600;800&display=swap";:root{--bg-main: #0f172a;--bg-card: #1e293b;--text-primary: #f8fafc;--text-secondary: #94a3b8;--accent-blue: #3b82f6;--accent-green: #10b981;--border: #334155;--font-main: "Inter", sans-serif}body{margin:0;background-color:var(--bg-main);color:var(--text-primary);font-family:var(--font-main);-webkit-font-smoothing:antialiased}*{box-sizing:border-box}.container{max-width:1200px;margin:0 auto;padding:20px}.btn-primary{background:var(--accent-blue);color:#fff;border:none;padding:10px 20px;border-radius:8px;font-weight:600;cursor:pointer;display:flex;align-items:center;gap:8px;transition:opacity .2s}.btn-primary:hover{opacity:.9}.btn-secondary{background:var(--bg-card);color:var(--text-primary);border:1px solid var(--border);padding:10px 20px;border-radius:8px;font-weight:600;cursor:pointer;display:flex;align-items:center;gap:8px;transition:background .2s}.btn-secondary:hover{background:#2a3850}.input-field{background:var(--bg-main);border:1px solid var(--border);color:#fff;padding:10px;border-radius:6px;width:100%;font-family:var(--font-main)}.card{background:var(--bg-card);border:1px solid var(--border);border-radius:12px;padding:20px}@media print{@page{margin:0;size:auto}body{margin:0}body *{visibility:hidden}#invoice-preview,#invoice-preview *{visibility:visible}#invoice-preview{position:absolute;left:0;top:0;width:100%;margin:0;padding:20mm;background:#fff;color:#000;border:none;box-shadow:none!important}.invoice-card{background:#fff!important;color:#000!important;box-shadow:none!important}}@keyframes spin{0%{transform:rotate(0)}to{transform:rotate(360deg)}}.spin{animation:spin 1s linear infinite}@media(max-width:768px){.app-container{flex-direction:column}.mobile-header{display:flex!important;position:sticky;top:0;z-index:999}.sidebar{position:fixed;top:0;left:0;bottom:0;width:280px!important;z-index:1000;transform:translate(-100%);transition:transform .3s ease-in-out;box-shadow:2px 0 10px #00000080}.sidebar.open{transform:translate(0)}.sidebar.open:before{content:"";position:fixed;top:0;left:280px;right:-100vw;bottom:0;background:#00000080;pointer-events:auto}main{padding:16px!important;width:100%;overflow-x:hidden}.card{padding:16px}.invoice-grid{grid-template-columns:1fr!important;gap:20px!important}.invoice-preview-container{overflow-x:auto;border:1px solid var(--border);border-radius:8px}#invoice-preview{min-width:800px;transform:scale(.8);transform-origin:top left}.stats-grid{grid-template-columns:1fr 1fr!important}.math-keyboard{grid-template-columns:repeat(4,1fr)!important;gap:6px!important}.math-keyboard button{padding:12px 0!important;font-size:1.2rem!important}}