@import url('https://fonts.googleapis.com/css2?family=Inter:wght@300;400;500;600&display=swap');

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
    --bg-body:      #1c1c1c;
    --bg-calc:      #1f1f1f;
    --bg-sidebar:   #181818;
    --bg-display:   #0a0a0a;
    --bg-num:       #2e2e2e;
    --bg-fn:        #262626;
    --bg-mem:       #222222;
    --bg-op:        #3a3a3a;
    --bg-sci:       #1a2230;
    --bg-eq:        #ff9500;
    --bg-eq-hover:  #ffaa28;
    --clr-text:     #f0f0f0;
    --clr-muted:    #888888;
    --clr-accent:   #ff9500;
    --clr-sci:      #7ecfff;
    --btn-hover:    #444;
    --btn-active:   #1a1a1a;
    --gap:          1px;
    --sidebar-w:    220px;
    --calc-w:       420px;
}

body {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    background: linear-gradient(135deg, #1a1a1a, #000000, #1a1a1a);
    font-family: 'Inter', 'Segoe UI', sans-serif;
    transition: background 0.3s;
}

/* ─── LIGHT THEME ────────────────────────────── */
body.light {
    --bg-body:     #e8e8e8;
    --bg-calc:     #ffffff;
    --bg-sidebar:  #f5f5f5;
    --bg-display:  #f0f0f0;
    --bg-num:      #ededed;
    --bg-fn:       #e4e4e4;
    --bg-mem:      #e0e0e0;
    --bg-op:       #d8d8d8;
    --bg-sci:      #dceeff;
    --clr-text:    #111111;
    --clr-muted:   #666666;
    --clr-sci:     #1a6faa;
    --btn-hover:   #d0d0d0;
    --btn-active:  #c4c4c4;
    background: linear-gradient(135deg, #f5f5f5, #e0e0e0, #f5f5f5);
}

/* ─── APP WRAPPER ────────────────────────────── */
#app {
    display: flex;
    align-items: stretch;
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 16px 56px rgba(0,0,0,0.65);
}

/* ─── CALCULATOR ─────────────────────────────── */
#calculator {
    width: var(--calc-w);
    background: var(--bg-calc);
    display: flex;
    flex-direction: column;
    transition: background 0.3s;
}

/* ─── TITLEBAR ───────────────────────────────── */
#titlebar {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 13px 16px 10px;
    background: var(--bg-calc);
    transition: background 0.3s;
}

#calc-title {
    font-size: 20px;
    font-weight: 600;
    color: var(--clr-text);
    letter-spacing: 0.2px;
}

#titlebar-controls { display: flex; gap: 7px; }

#theme-toggle {
    padding: 5px 13px;
    font-size: 11.5px;
    font-weight: 500;
    color: var(--clr-text);
    background: var(--bg-fn);
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: background 0.15s, color 0.15s;
    width: auto; height: auto; box-shadow: none;
}
#theme-toggle:hover  { background: var(--btn-hover); color: var(--clr-text); transform: none; }
#theme-toggle:active { background: var(--btn-active); transform: none; box-shadow: none; }

/* ─── MODE SWITCHER ─────────────────────────── */
#mode-switcher {
    display: flex;
    background: var(--bg-display);
    border-radius: 6px;
    padding: 2px;
    gap: 2px;
}

.mode-btn {
    padding: 4px 12px;
    font-size: 11.5px;
    font-weight: 500;
    color: var(--clr-muted);
    background: transparent;
    border: none;
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: background 0.15s, color 0.15s;
    width: auto; height: auto; box-shadow: none;
}
.mode-btn:hover  { color: var(--clr-text); transform: none; filter: none; }
.mode-btn:active { transform: none; box-shadow: none; filter: none; }
.mode-btn.active { background: var(--clr-accent); color: #fff; }



/* ─── DISPLAY ────────────────────────────────── */
#display-area {
    background: var(--bg-display);
    padding: 12px 20px 8px;
    min-height: 120px;
    display: flex;
    flex-direction: column;
    justify-content: flex-end;
    align-items: flex-end;
    transition: background 0.3s;
    position: relative;
}

#last_operation_history {
    font-size: 18px;
    color: var(--clr-muted);
    min-height: 24px;
    text-align: right;
    width: 100%;
    background: transparent;
    transition: color 0.3s;
    font-weight: 300;
    opacity: 0.75;
    letter-spacing: 0.2px;
}

.box {
    font-size: 68px;
    font-weight: 300;
    color: var(--clr-text);
    text-align: right;
    width: 100%;
    background: transparent;
    border: none;
    line-height: 1.05;
    word-break: break-all;
    transition: color 0.3s, font-size 0.1s;
    animation: glow-pulse 3s ease-in-out infinite alternate;
}

@keyframes glow-pulse {
    from { text-shadow: 0 0 8px rgba(255,149,0,0.6); }
    to   { text-shadow: 0 0 22px rgba(255,149,0,0.95), 0 0 40px rgba(255,149,0,0.3); }
}

#display-actions {
    display: flex;
    gap: 6px;
    align-items: center;
    width: 100%;
    justify-content: space-between;
    margin-top: 6px;
}

#memory-display {
    font-size: 11px;
    color: var(--clr-accent);
    font-weight: 500;
    flex: 1;
}

#copy-btn, #sound-btn {
    padding: 3px 9px;
    font-size: 11px;
    font-weight: 500;
    color: var(--clr-muted);
    background: transparent;
    border: 1px solid rgba(255,255,255,0.12);
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: all 0.15s;
    width: auto; height: auto; box-shadow: none;
    white-space: nowrap;
}
#copy-btn:hover, #sound-btn:hover  { background: var(--btn-hover); color: var(--clr-text); border-color: transparent; transform: none; }
#copy-btn:active, #sound-btn:active { transform: none; box-shadow: none; }
body.light #copy-btn, body.light #sound-btn { border-color: rgba(0,0,0,0.15); }
#sound-btn.muted { color: #ff4444; border-color: rgba(255,68,68,0.3); }

/* ─── SCIENTIFIC PANEL ───────────────────────── */
#sci-panel {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--gap);
    background: #111;
    border-top: 1px solid #111;
    max-height: 0;
    overflow: hidden;
    transition: max-height 0.3s ease, opacity 0.3s ease;
    opacity: 0;
}

#sci-panel.visible { max-height: 120px; opacity: 1; }

.sci-btn {
    background: var(--bg-sci);
    color: var(--clr-sci);
    font-size: 14px;
    font-weight: 600;
    height: 52px;
    width: 100%;
    border: none;
    border-radius: 0;
    cursor: pointer;
    font-family: inherit;
    letter-spacing: 0.3px;
    transition: filter 0.1s, transform 0.08s, box-shadow 0.08s;
    display: flex;
    align-items: center;
    justify-content: center;
}
.sci-btn:hover  { filter: brightness(1.25); }
.sci-btn:active {
    transform: scale(0.93);
    box-shadow: inset 2px 2px 6px rgba(0,0,0,0.5);
    filter: brightness(0.85);
}

/* ─── KEYPAD ─────────────────────────────────── */
#keypad {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: var(--gap);
    background: #111;
    border-top: 1px solid #111;
    flex: 1;
}

/* ─── BASE BUTTON ────────────────────────────── */
#keypad button {
    width: 100%;
    height: 68px;
    font-size: 20px;
    font-weight: 400;
    font-family: inherit;
    color: var(--clr-text);
    border: none;
    border-radius: 0;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: none;
    transition: filter 0.1s, transform 0.08s, box-shadow 0.08s;
}

#keypad button:hover  { filter: brightness(1.22); box-shadow: 0 0 8px rgba(255,149,0,0.35); }
#keypad button:active {
    transform: scale(0.92);
    box-shadow: inset 3px 3px 8px #000;
    filter: brightness(0.78);
}

button.flash { animation: flash-key 0.18s ease; }
@keyframes flash-key {
    0%   { filter: brightness(2.4); }
    100% { filter: brightness(1);   }
}

/* ─── BUTTON TYPES ───────────────────────────── */
.mem-btn { background: var(--bg-mem); font-size: 13px; color: var(--clr-muted); height: 54px !important; }
.fn-btn  { background: var(--bg-fn);  font-size: 17px; }
.num-btn { background: var(--bg-num); font-size: 22px; font-weight: 500; }
.op-btn  { background: var(--bg-op);  font-size: 22px; }

.eq-btn {
    background: var(--bg-eq);
    color: #fff;
    font-size: 26px;
    font-weight: 600;
}
.eq-btn:hover { background: var(--bg-eq-hover) !important; filter: none !important; }

.wide-btn { grid-column: span 2; }
.operator { transition: background 0.2s, color 0.2s, box-shadow 0.2s; }
.operator.selected {
    background: #ff9500 !important;
    color: #fff !important;
    box-shadow: 0 0 15px rgba(255,149,0,0.75), 0 0 30px rgba(255,149,0,0.3);
}

/* ─── HISTORY SIDEBAR ────────────────────────── */
#history-sidebar {
    width: var(--sidebar-w);
    background: var(--bg-sidebar);
    display: flex;
    flex-direction: column;
    border-left: 1px solid rgba(255,255,255,0.05);
    transition: background 0.3s;
}

body.light #history-sidebar { border-left-color: rgba(0,0,0,0.08); }

#history-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 14px 12px;
    border-bottom: 1px solid rgba(255,255,255,0.06);
    flex-shrink: 0;
    transition: border-color 0.3s;
}

body.light #history-header { border-bottom-color: rgba(0,0,0,0.08); }

#history-header span {
    font-size: 13px;
    font-weight: 600;
    color: var(--clr-text);
    letter-spacing: 0.5px;
    text-transform: uppercase;
}

#history-clear-btn {
    padding: 4px 10px;
    font-size: 11px;
    font-weight: 500;
    color: var(--clr-muted);
    background: transparent;
    border: 1px solid rgba(255,255,255,0.15);
    border-radius: 4px;
    cursor: pointer;
    font-family: inherit;
    transition: all 0.15s;
    width: auto; height: auto; box-shadow: none;
}
#history-clear-btn:hover  { background: var(--btn-hover); color: var(--clr-text); border-color: transparent; transform: none; }
#history-clear-btn:active { background: var(--btn-active); transform: none; box-shadow: none; }
body.light #history-clear-btn { border-color: rgba(0,0,0,0.15); }

#history-panel {
    flex: 1;
    overflow-y: auto;
    padding: 4px 0;
}

#history-empty {
    text-align: center;
    color: var(--clr-muted);
    font-size: 12px;
    padding: 32px 16px;
    line-height: 1.6;
    opacity: 0.55;
}

#history-panel p {
    font-size: 12px;
    color: var(--clr-muted);
    text-align: right;
    padding: 8px 12px;
    margin: 4px 8px;
    border-radius: 6px;
    background: #111;
    border-bottom: none;
    transition: background 0.15s;
    cursor: default;
    line-height: 1.4;
}
#history-panel p .result-line {
    display: block;
    font-size: 17px;
    font-weight: 500;
    color: var(--clr-text);
    margin-top: 3px;
}
#history-panel p:hover { background: #222; }
body.light #history-panel p       { background: #e8e8e8; }
body.light #history-panel p:hover { background: #d8d8d8; }


/* ─── SCROLLBAR ──────────────────────────────── */
#history-panel::-webkit-scrollbar       { width: 3px; }
#history-panel::-webkit-scrollbar-track { background: transparent; }
#history-panel::-webkit-scrollbar-thumb { background: #444; border-radius: 2px; }

/* ─── RESPONSIVE ─────────────────────────────── */
@media (max-width: 700px) {
    #app              { flex-direction: column; border-radius: 0; width: 100vw; }
    #calculator       { width: 100%; }
    #history-sidebar  { width: 100%; border-left: none; border-top: 1px solid #111; max-height: 180px; }
    #keypad button    { height: 14.5vw; font-size: 5vw; }
    .mem-btn          { height: 11vw !important; }
    .box              { font-size: 12vw; }
}