:root {
  color-scheme: dark;
  --bg: #101318;
  --surface: #181d24;
  --surface-soft: #12171d;
  --surface-raised: #20262f;
  --line: #303844;
  --line-strong: #485363;
  --text: #f3f5f7;
  --muted: #9ba5b2;
  --accent: #5f86bd;
  --accent-strong: #456dA7;
  --danger: #c96b6b;
  --shadow: 0 20px 55px rgba(0, 0, 0, 0.3);
}

body[data-theme="light"] {
  color-scheme: light;
  --bg: #eef1f4;
  --surface: #ffffff;
  --surface-soft: #f5f7f9;
  --surface-raised: #edf1f5;
  --line: #d8dde3;
  --line-strong: #b8c1cc;
  --text: #18202a;
  --muted: #626d7a;
  --accent: #3e659b;
  --accent-strong: #315581;
  --danger: #a54a4a;
  --shadow: 0 18px 42px rgba(28, 37, 48, 0.1);
}

* { box-sizing: border-box; }
html, body { margin: 0; min-height: 100%; }
body { min-height: 100vh; background: var(--bg); color: var(--text); font-family: Inter, ui-sans-serif, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif; }
button, textarea, a { font: inherit; }
button:focus-visible, textarea:focus-visible, a:focus-visible { outline: 3px solid color-mix(in srgb, var(--accent) 35%, transparent); outline-offset: 2px; }

.calc-shell { width: min(1320px, 100%); min-height: 100vh; margin: 0 auto; padding: 28px; }
.app-header { min-height: 76px; display: flex; align-items: center; justify-content: space-between; gap: 24px; margin-bottom: 20px; }
.brand-block { display: flex; align-items: center; gap: 15px; }
.brand-mark { width: 42px; height: 42px; display: grid; place-items: center; border: 1px solid var(--line-strong); border-radius: 10px; background: var(--surface); color: var(--accent); font: 700 1.35rem ui-monospace, SFMono-Regular, Consolas, monospace; }
.brand-block p, .brand-block h1 { margin: 0; }
.brand-block p { color: var(--muted); font-size: 0.7rem; font-weight: 760; letter-spacing: 0.13em; text-transform: uppercase; }
.brand-block h1 { margin-top: 3px; font-size: 1.75rem; letter-spacing: -0.035em; }
.header-actions { display: flex; align-items: center; gap: 10px; }
.header-button, .home-link { min-height: 40px; padding: 0 14px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); color: var(--text); font-weight: 650; }
.header-button { cursor: pointer; }
.home-link { display: inline-flex; align-items: center; text-decoration: none; }
.header-button:hover, .home-link:hover { border-color: var(--line-strong); }

.calc-workspace { display: grid; grid-template-columns: minmax(0, 1fr) minmax(270px, 330px); gap: 16px; align-items: start; }
.calc-board, .history-panel { border: 1px solid var(--line); border-radius: 14px; background: var(--surface); box-shadow: var(--shadow); }
.calc-board { min-width: 0; padding: 24px; }

.result-panel { min-height: 172px; display: flex; flex-direction: column; align-items: flex-end; justify-content: center; padding: 20px 22px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface-soft); }
.result-toolbar { align-self: stretch; display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-bottom: auto; color: var(--muted); font-size: 0.72rem; font-weight: 720; letter-spacing: 0.08em; text-transform: uppercase; }
.scale-label { padding-left: 12px; border-left: 1px solid var(--line); }
.result-main { max-width: 100%; margin-top: 18px; font: 620 clamp(2.6rem, 6vw, 5.2rem)/1 ui-monospace, SFMono-Regular, Consolas, monospace; font-variant-numeric: tabular-nums; letter-spacing: -0.055em; white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
.result-secondary { min-height: 20px; margin-top: 9px; color: var(--muted); font-size: 0.86rem; text-align: right; }

.expression-panel { margin-top: 14px; padding: 18px; border: 1px solid var(--line); border-radius: 10px; }
.expression-panel > label { display: block; margin-bottom: 8px; color: var(--muted); font-size: 0.7rem; font-weight: 750; letter-spacing: 0.09em; text-transform: uppercase; }
#expressionInput { width: 100%; min-height: 86px; resize: vertical; padding: 12px 13px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface-soft); color: var(--text); font: 560 1rem/1.55 ui-monospace, SFMono-Regular, Consolas, monospace; }
#expressionInput:focus { border-color: var(--accent); }
#expressionInput::placeholder { color: var(--muted); opacity: 0.75; }
.input-toolbar { display: flex; align-items: center; justify-content: space-between; gap: 12px; margin-top: 10px; }
.input-toolbar > div { display: flex; flex-wrap: wrap; gap: 7px; justify-content: flex-end; }
.screen-note { color: var(--muted); font-size: 0.8rem; }
.input-toolbar button, .advanced-tools button { min-height: 34px; padding: 0 11px; border: 1px solid var(--line); border-radius: 7px; background: var(--surface-raised); color: var(--text); font-size: 0.79rem; font-weight: 650; cursor: pointer; }
.input-toolbar button:hover, .advanced-tools button:hover { border-color: var(--line-strong); }

.keypad-grid { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 8px; margin-top: 14px; }
.keypad-button { min-height: 58px; border: 1px solid var(--line); border-radius: 9px; background: var(--surface-raised); color: var(--text); font-size: 1.05rem; font-weight: 650; cursor: pointer; }
.keypad-button:hover { border-color: var(--line-strong); background: color-mix(in srgb, var(--surface-raised) 88%, var(--text)); }
.keypad-button.operator { color: var(--accent); font-size: 1.2rem; }
.keypad-button.function { color: var(--muted); }
.keypad-button.zero { grid-column: span 2; }
.keypad-button.equals { grid-column: span 2; border-color: var(--accent-strong); background: var(--accent-strong); color: #fff; font-size: 1.25rem; }

.advanced-tools { display: grid; gap: 10px; margin-top: 14px; padding: 15px 0; border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.advanced-tools > span { color: var(--muted); font-size: 0.7rem; font-weight: 750; letter-spacing: 0.09em; text-transform: uppercase; }
.advanced-tools > div { display: flex; flex-wrap: wrap; gap: 7px; }
.primary-action { width: 100%; min-height: 50px; margin-top: 14px; border: 1px solid var(--accent-strong); border-radius: 9px; background: var(--accent-strong); color: #fff; font-weight: 740; cursor: pointer; }
.primary-action:hover { background: color-mix(in srgb, var(--accent-strong) 88%, white); }

.history-panel { min-height: 420px; padding: 20px; }
.panel-head { display: flex; align-items: center; justify-content: space-between; gap: 14px; padding-bottom: 16px; border-bottom: 1px solid var(--line); }
.panel-head div { display: grid; gap: 4px; }
.panel-head span { color: var(--muted); font-size: 0.68rem; font-weight: 750; letter-spacing: 0.1em; text-transform: uppercase; }
.panel-head h2 { margin: 0; font-size: 1.15rem; }
.panel-head > strong { min-width: 34px; height: 28px; display: grid; place-items: center; border: 1px solid var(--line); border-radius: 7px; color: var(--muted); font-size: 0.82rem; }
.history-list { display: grid; gap: 8px; max-height: 560px; margin-top: 16px; overflow: auto; }
.history-empty { padding: 32px 8px; color: var(--muted); font-size: 0.86rem; text-align: center; }
.history-item { display: grid; gap: 5px; padding: 12px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface-soft); cursor: pointer; }
.history-item:hover { border-color: var(--line-strong); }
.history-item time { color: var(--muted); font-size: 0.68rem; font-weight: 700; letter-spacing: 0.08em; text-transform: uppercase; }
.history-item strong { font: 620 0.86rem ui-monospace, SFMono-Regular, Consolas, monospace; overflow-wrap: anywhere; }
.history-item span { color: var(--muted); font-size: 0.78rem; overflow-wrap: anywhere; }
.session-meta { display: flex; justify-content: space-between; gap: 12px; margin-top: 18px; padding-top: 14px; border-top: 1px solid var(--line); color: var(--muted); font-size: 0.78rem; }
.session-meta strong { color: var(--text); }

@media (max-width: 900px) { .calc-workspace { grid-template-columns: 1fr; } .history-panel { min-height: 0; } }
@media (max-width: 620px) {
  .calc-shell { padding: 14px; }
  .app-header { align-items: flex-start; }
  .header-actions { flex-direction: column; align-items: stretch; }
  .calc-board, .history-panel { padding: 16px; }
  .result-panel { min-height: 145px; padding: 16px; }
  .result-main { font-size: clamp(2rem, 13vw, 3.6rem); }
  .input-toolbar { align-items: flex-start; flex-direction: column; }
  .input-toolbar > div { justify-content: flex-start; }
  .keypad-grid { grid-template-columns: repeat(4, minmax(0, 1fr)); }
  .keypad-button { min-height: 52px; }
}

@media (prefers-reduced-motion: reduce) { * { transition-duration: 0.01ms !important; } }