/* --- CALCULATOR CONTAINER --- */
.calc-wrapper {
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding-bottom: 4rem;
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
}

.calc-container {
    width: 100%;
    max-width: 380px; /* Standard Mode Width */
    background: #18181b; /* Darker, modern background */
    border-radius: 24px; /* Apple-like rounded corners */
    box-shadow: 0 30px 60px -12px rgba(0, 0, 0, 0.6);
    padding: 20px; /* Internal padding for floating look */
    border: 1px solid #333;
    transition: max-width 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
}

/* Wider container for Sci/Prog modes */
.calc-container.wide-mode {
    max-width: 620px;
}

/* --- SCREEN AREA --- */
.calc-screen {
    background: transparent; /* Seamless look */
    color: #fff;
    padding: 0 10px 20px 10px;
    text-align: right;
    border-bottom: 1px solid #333;
    margin-bottom: 20px;
}

.calc-history {
    font-size: 0.9rem;
    color: #a1a1aa;
    min-height: 1.5rem;
    margin-bottom: 0.2rem;
    font-weight: 500;
}

.calc-output {
    font-size: 3.5rem;
    font-weight: 300;
    line-height: 1.1;
    word-break: break-all;
    letter-spacing: -1px;
}

/* --- TABS --- */
.mode-tabs {
    display: flex;
    background: #27272a;
    border-radius: 12px;
    padding: 4px;
    margin-bottom: 20px;
}

.mode-tab {
    flex: 1;
    padding: 8px;
    background: none;
    border: none;
    color: #a1a1aa;
    cursor: pointer;
    font-size: 0.75rem;
    text-transform: uppercase;
    font-weight: 700;
    border-radius: 8px;
    transition: all 0.2s ease;
}

.mode-tab:hover {
    color: #fff;
}

.mode-tab.active {
    color: #fff;
    background: #3f3f46;
    box-shadow: 0 2px 5px rgba(0,0,0,0.2);
}

/* --- BASE SWITCHER (Programmer) --- */
.base-switch-container {
    display: none;
    background: #202022;
    padding: 10px;
    border-radius: 12px;
    margin-bottom: 20px;
    border: 1px solid #333;
}

.base-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 6px 10px;
    cursor: pointer;
    color: #71717a;
    font-family: 'Inter', monospace;
    font-size: 0.85rem;
    border-radius: 6px;
    margin-bottom: 2px;
    transition: 0.2s;
}

.base-row:hover { background: #27272a; color: #fff; }
.base-row.active { color: var(--accent, #3b82f6); background: rgba(59, 130, 246, 0.1); font-weight: 700; }
.base-label { font-weight: 700; }
.base-val { font-family: monospace; }

/* --- KEYPAD GRID --- */
.keypad {
    display: grid;
    grid-template-columns: repeat(4, 1fr); /* Standard Grid */
    gap: 12px; /* Gaps between buttons */
}

/* 6 Columns for Scientific / Programmer */
.keypad.scientific-grid,
.keypad.programmer-grid {
    grid-template-columns: repeat(6, 1fr);
}

/* --- BUTTONS --- */
.btn-calc {
    background: #27272a; /* Dark Grey */
    border: none;
    height: 60px;
    border-radius: 14px; /* Rounded Buttons */
    font-size: 1.25rem;
    color: #fff;
    cursor: pointer;
    transition: all 0.1s ease;
    user-select: none;
    display: flex;
    align-items: center;
    justify-content: center;
    box-shadow: 0 4px 0 rgba(0,0,0,0.2); /* Subtle 3D effect */
}

.btn-calc:active, .btn-calc.pressed {
    transform: translateY(2px);
    box-shadow: none;
    background: #3f3f46;
}

.btn-calc:hover {
    background: #3f3f46;
}

/* --- BUTTON TYPES --- */

/* Numbers */
.num-key {
    background: #27272a;
    font-weight: 400;
}

/* Operators (Accent Color) */
.btn-op {
    background: rgba(59, 130, 246, 0.15); /* Tinted Accent */
    color: var(--accent, #3b82f6);
    font-weight: 600;
    font-size: 1.4rem;
}
.btn-op:hover { background: rgba(59, 130, 246, 0.3); }

/* Equals Button (Solid Accent) */
.btn-eq {
    background: var(--accent, #3b82f6);
    color: #fff;
    font-weight: 700;
}
.btn-eq:hover { background: #2563eb; }

/* Clear/Delete (Red tint) */
.btn-clear {
    background: rgba(239, 68, 68, 0.15);
    color: #f87171;
    font-size: 1rem;
    font-weight: 600;
}
.btn-clear:hover { background: rgba(239, 68, 68, 0.25); }

/* Scientific Keys (Subtle) */
.btn-sci {
    background: #18181b; /* Darker than numbers to visually recede */
    color: #a1a1aa;
    font-size: 0.95rem;
    font-weight: 600;
    box-shadow: none;
    border: 1px solid #27272a;
}
.btn-sci:hover { color: #fff; border-color: #52525b; }

/* Programmer Keys (Purple Tint) */
.btn-hex {
    background: #18181b;
    color: #c084fc;
    font-size: 1rem;
    font-weight: 600;
    border: 1px solid #27272a;
    box-shadow: none;
}
.btn-hex:hover { border-color: #c084fc; }

.btn-calc:disabled {
    opacity: 0.2;
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

/* Visibility Helpers */
.sci-key, .prog-key { display: none; }
.sci-key.visible, .prog-key.visible { display: flex; } /* Flex to center text */

/* Mobile Responsiveness */
@media (max-width: 600px) {
    .calc-container { padding: 15px; border-radius: 20px; }
    .btn-calc { height: 50px; font-size: 1rem; border-radius: 10px; }
    .keypad { gap: 8px; }
    .calc-output { font-size: 2.5rem; }
}