/* ================================
   π记忆挑战 - 自定义样式
   ================================ */
:root{--bg:#FAFAF9;--bg-alt:#F5F5F4;--surface:#FFFFFF;--border:#E7E5E4;--border-strong:#D6D3D1;--text:#1E293B;--text-secondary:#52525B;--text-muted:#71717A;--primary:#4F46E5;--primary-hover:#4338CA;--primary-light:rgba(79,70,229,.08);--secondary:#F97316;--accent:#EC4899;--success:#059669;--radius:10px;--radius-lg:14px}
*{margin:0;padding:0;box-sizing:border-box}
html{scroll-behavior:smooth}
body{font-family:'Inter','Noto Sans SC',system-ui,sans-serif;background:var(--bg);color:var(--text);line-height:1.6;min-height:100vh;-webkit-font-smoothing:antialiased}
.toast{position:fixed;top:24px;right:24px;background:var(--text);color:var(--bg);padding:10px 18px;border-radius:100px;font-size:14px;font-weight:500;display:flex;align-items:center;gap:8px;z-index:1000;transform:translateX(calc(100% + 40px));transition:transform .3s cubic-bezier(.34,1.56,.64,1);box-shadow:0 4px 16px rgba(0,0,0,.12)}
.toast.show{transform:translateX(0)}.toast-dot{width:8px;height:8px;background:var(--success);border-radius:50%}
.page{max-width:960px;margin:0 auto;padding:0 32px}
.tool-section{padding:32px 0 24px}
.tool-wrapper{display:flex;flex-direction:column;gap:24px}
.panel{background:var(--surface);border:1px solid var(--border);border-radius:var(--radius-lg);padding:24px;box-shadow:0 4px 12px rgba(0,0,0,.06)}
.panel-title{font-size:16px;font-weight:700;color:var(--text);margin-bottom:16px}
.difficulty-select{display:flex;gap:8px;flex-wrap:wrap;margin-bottom:20px}
.diff-btn{padding:8px 18px;border:1px solid var(--border);border-radius:100px;font-family:inherit;font-size:13px;font-weight:500;cursor:pointer;background:transparent;color:var(--text-muted);transition:all .15s ease}
.diff-btn:hover{border-color:var(--primary);color:var(--primary)}
.diff-btn.active{background:var(--primary);border-color:var(--primary);color:#fff}
.pi-ref{font-family:'SF Mono','Cascadia Code',monospace;font-size:22px;letter-spacing:.08em;line-height:1.8;word-break:break-all;padding:20px;background:var(--bg-alt);border-radius:var(--radius);border:1px solid var(--border);margin-bottom:20px;color:var(--text);text-align:center;min-height:80px}
.input-area{display:flex;gap:12px;margin-bottom:16px}
.pi-input{flex:1;padding:12px 14px;font-family:'SF Mono','Cascadia Code',monospace;font-size:18px;border:2px solid var(--border);border-radius:var(--radius);text-align:center;letter-spacing:.1em;outline:none;transition:border-color .2s}
.pi-input:focus{border-color:var(--primary)}
.pi-input.correct{border-color:var(--success);background:rgba(5,150,105,.04)}
.pi-input.wrong{border-color:#EF4444;background:rgba(239,68,68,.04);animation:shake .4s ease}
@keyframes shake{0%,100%{transform:translateX(0)}25%{transform:translateX(-6px)}75%{transform:translateX(6px)}}
.stats{display:flex;gap:24px;flex-wrap:wrap;margin-bottom:16px}
.stat-item{display:flex;flex-direction:column}
.stat-label{font-size:11px;text-transform:uppercase;letter-spacing:.06em;color:var(--text-muted);font-weight:600}
.stat-value{font-size:28px;font-weight:700;color:var(--text)}
.btn{padding:12px 28px;border-radius:100px;font-family:inherit;font-size:15px;font-weight:600;cursor:pointer;transition:all .2s ease;border:none}
.btn-primary{background:linear-gradient(135deg,#818CF8 0%,#7C3AED 100%);color:#fff;box-shadow:0 4px 12px rgba(124,58,237,.3)}
.btn-primary:hover{transform:translateY(-2px);box-shadow:0 8px 20px rgba(124,58,237,.4)}
.btn-secondary{background:var(--bg-alt);color:var(--text-secondary);border:1px solid var(--border)}
.btn-secondary:hover{background:var(--primary-light);border-color:rgba(79,70,229,.25)}
.guide-section{margin-top:16px;margin-bottom:64px;background:#fff;border:1px solid var(--border);border-radius:12px;overflow:hidden}
.guide-toggle{display:flex;align-items:center;justify-content:space-between;width:100%;padding:14px 20px;background:none;border:none;cursor:pointer;transition:background .15s ease}
.guide-toggle:hover{background:var(--bg-alt)}
.guide-toggle-title{display:flex;align-items:center;gap:8px;font-size:14px;font-weight:600;color:#1E293B}
.guide-toggle.open .toggle-arrow{transform:rotate(180deg)}
.toggle-arrow{transition:transform .2s ease;color:var(--text-muted)}
.guide-list{padding:0 20px 20px}.guide-list.hidden{display:none}
.guide-item{padding:16px 0;border-top:1px solid var(--border)}
.guide-item-title{font-size:14px;font-weight:600;color:#1E293B;margin-bottom:6px}
.guide-item-body{font-size:13px;color:var(--text-secondary);line-height:1.8}
::-webkit-scrollbar{width:8px}::-webkit-scrollbar-track{background:#f1f5f9}::-webkit-scrollbar-thumb{background:#A5B4FC;border-radius:4px}
::selection{background:rgba(79,70,229,.2);color:#1E293B}
@media(max-width:768px){.page{padding:0 16px}.pi-ref{font-size:16px;padding:12px}.stats{gap:16px}.stat-value{font-size:22px}}