:root{--bg:#f4f7fb;--surface:#fff;--surface-2:#f8fafc;--ink:#172033;--muted:#7e8b9f;--line:#e8edf4;--navy:#101827;--blue:#4d72f5;--blue-soft:#edf1ff;--shadow:0 18px 50px rgba(29,45,77,.08)}*{box-sizing:border-box}body{margin:0;background:var(--bg);color:var(--ink);font:14px Inter,ui-sans-serif,system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",sans-serif;min-height:100vh}button,a{font:inherit}button{cursor:pointer;border:0}a{text-decoration:none;color:inherit}.app-shell{display:flex;min-height:100vh}.sidebar{width:244px;background:var(--navy);color:#fff;padding:28px 18px 24px;display:flex;flex-direction:column}.brand{display:flex;align-items:center;gap:10px;font-size:22px;font-weight:750;letter-spacing:-.7px;padding:0 13px 42px}.brand-mark{width:29px;height:29px;border-radius:9px;background:var(--blue);display:grid;place-items:center;font-size:22px;font-weight:400;box-shadow:0 5px 16px #425fd080}.main-nav{display:grid;gap:7px}.nav-item{display:flex;align-items:center;gap:14px;border-radius:10px;padding:12px 14px;color:#98a5bb;transition:.2s}.nav-item:hover,.nav-item.active{background:#1d2a40;color:#fff}.nav-item.active{box-shadow:inset 3px 0 var(--blue)}.nav-icon{width:18px;text-align:center;font-size:19px;color:currentColor}.sidebar-bottom{margin-top:auto}.tip-card{margin:0 5px 24px;padding:16px;background:#17253a;border:1px solid #263650;border-radius:12px;color:#aebbd0}.tip-card strong{display:block;color:#fff;font-size:12px;margin:8px 0 5px}.tip-card p{font-size:11px;line-height:1.5;margin:0}.tip-spark{color:#93aaff;font-size:18px}.help-link{display:flex;justify-content:space-between;padding:0 14px;color:#93a0b5;font-size:12px}.help-link span{font-size:18px;color:#fff}.main-content{flex:1;max-width:1440px;margin:0 auto;padding:36px 5.4% 60px}.topbar{display:flex;justify-content:space-between;align-items:center;margin-bottom:36px}.eyebrow{text-transform:uppercase;letter-spacing:1.5px;font-size:10px;color:var(--muted);font-weight:750;margin:0 0 7px}.topbar h1{font-size:29px;letter-spacing:-1px;margin:0}.top-actions{display:flex;align-items:center;gap:17px}.icon-button{height:38px;width:38px;border-radius:10px;background:var(--surface);color:var(--muted);font-size:20px;box-shadow:0 3px 15px rgba(30,47,80,.05)}.avatar{width:38px;height:38px;border-radius:50%;display:grid;place-items:center;background:#dce5ff;color:#4b67c4;font-size:12px;font-weight:750}.content-grid{display:grid;grid-template-columns:minmax(420px,650px) minmax(280px,385px);gap:34px;align-items:start}.calculator-card,.history-panel{background:var(--surface);border:1px solid var(--line);box-shadow:var(--shadow);border-radius:18px}.calculator-card{padding:25px 27px 21px}.mode-row{display:flex;justify-content:space-between;align-items:center;margin-bottom:24px}.segmented-control{background:var(--surface-2);padding:4px;border-radius:9px;display:flex;gap:2px}.segment{border-radius:7px;padding:8px 18px;color:var(--muted);font-size:12px;font-weight:650}.segment.active{background:var(--surface);color:var(--ink);box-shadow:0 2px 7px #24385812}.more-button{background:none;color:var(--muted);font-size:11px;font-weight:700;letter-spacing:.5px}.more-button span{font-size:15px;margin-left:5px}.display{background:#f5f7fb;border:1px solid #edf0f5;border-radius:13px;min-height:138px;padding:22px 24px;text-align:right;display:flex;flex-direction:column;justify-content:flex-end;overflow:hidden}.display-expression{color:#8793a7;font-size:19px;min-height:28px;white-space:nowrap;overflow:auto}.display-result{font-size:43px;font-weight:700;letter-spacing:-2px;line-height:1.1;white-space:nowrap;overflow:auto}.memory-row{height:53px;display:grid;grid-template-columns:repeat(5,1fr);align-items:center;gap:8px;border-bottom:1px solid var(--line)}.memory-row button{background:none;color:#91a0b5;font-size:11px;font-weight:750}.memory-row .backspace{color:#61708a;text-align:right;font-size:18px}.keypad{padding-top:21px;display:grid;grid-template-columns:repeat(4,1fr);gap:11px}.key{height:59px;border-radius:11px;background:var(--surface-2);color:var(--ink);font-size:19px;font-weight:600;transition:transform .1s,background .2s}.key:hover{background:#edf1f8}.key:active{transform:scale(.96)}.key.utility{color:#63738d;font-size:15px}.key.operator{background:var(--blue-soft);color:var(--blue);font-size:23px}.key.equals{background:var(--blue);color:#fff;font-size:24px;box-shadow:0 7px 15px #4d72f536}.keyboard-note{text-align:center;margin:20px 0 0;color:#a0aabc;font-size:11px}.keyboard-note span{margin:0 6px;color:#d6dce7}kbd{padding:2px 5px;background:#f0f2f6;border:1px solid #e2e6ed;border-radius:4px;font-size:10px}.history-panel{padding:25px 23px;min-height:420px}.panel-heading{display:flex;align-items:flex-start;justify-content:space-between;border-bottom:1px solid var(--line);padding-bottom:19px}.panel-heading h2{font-size:17px;margin:0;letter-spacing:-.3px}.clear-history{background:none;color:var(--blue);font-size:11px;font-weight:700;padding-top:4px}.history-list{min-height:286px}.empty-history{text-align:center;padding:79px 10px 40px;color:var(--muted)}.empty-history 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.nav-item{color:var(--muted)}.light-theme .nav-item:hover,.light-theme .nav-item.active{background:#edf1ff;color:var(--blue)}.light-theme .tip-card{background:#f4f6ff;border-color:#e4e9ff}.light-theme .tip-card strong{color:var(--ink)}@media(max-width:900px){.sidebar{width:208px}.main-content{padding-left:28px;padding-right:28px}.content-grid{grid-template-columns:1fr}.history-panel{min-height:0}.history-list{min-height:0}.empty-history{padding:35px}}@media(max-width:600px){.app-shell{display:block}.sidebar{width:100%;height:66px;padding:0 16px;display:flex;flex-direction:row;align-items:center}.brand{padding:0;font-size:20px}.main-nav{display:flex;margin-left:auto;gap:3px}.nav-item{padding:9px;color:#98a5bb}.nav-item span+.nav-item{margin:0}.nav-item:not(.active){font-size:0}.nav-item:not(.active) .nav-icon{font-size:18px}.nav-item.active{font-size:0}.nav-item.active .nav-icon{font-size:20px}.sidebar-bottom{display:none}.main-content{padding:25px 15px 35px}.topbar{margin-bottom:23px}.topbar h1{font-size:25px}.content-grid{gap:18px}.calculator-card{padding:18px 14px}.keypad{gap:8px}.key{height:56px}.display{min-height:125px;padding:17px}.display-result{font-size:37px}.history-panel{padding:20px}.top-actions{gap:9px}}