/* ===== THEME VARIABLES ===== */
:root {
    --bg-main: #0b0d12;
    --bg-calc: rgba(15, 19, 27, 0.4); /* semi-transparent for bg image to show */
    --bg-bar: rgba(12, 17, 24, 0.6);
    --bg-keys: rgba(10, 14, 22, 0.6);
    --color-text: #ffffff;
    --color-subtext: #cfd8e3;
    --color-op: #b8cffb;
    --color-fn: #9be4b1;
    --color-danger: #ffb1b1;
    --btn-primary: #25407a;
    --btn-equals: #2d6b4a;
    --radius: 18px;
    --gap: 6px;
}

/* ===== BASE ===== */
body {
    margin: 0;
    font-family: sans-serif;
    background: url('bg.jpeg') no-repeat center center fixed;
    background-size: cover;
    color: var(--color-text);
    display: grid;
    place-items: center;
    height: 100vh;
}

button {
    font: inherit;
    cursor: pointer;
}

/* ===== CALCULATOR ===== */
.calc {
    background: var(--bg-calc);
    border-radius: var(--radius);
    overflow: hidden;
    max-width: 500px;
    width: 100%;
    box-shadow: 0 10px 30px rgba(0,0,0,.45);
}

/* ===== HEADER ===== */
.bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 8px 12px;
    background: var(--bg-bar);
    color: var(--color-subtext);
}

.controls {
    display: flex;
    gap: var(--gap);
}

.toggle button, #modeSwitch {
    background: none;
    border: none;
    padding: 4px 8px;
    color: var(--color-subtext);
    border-radius: 999px;
    transition: transform 0.15s ease, background-color 0.15s ease;
}
.toggle button:hover, #modeSwitch:hover {
    background: rgba(243, 23, 23, 0.1);
    transform: scale(1.05);
}

.toggle .active {
    background: #7aa2ff;
    color: #000;
}

/* ===== DISPLAY ===== */
.display {
    padding: 15px 20px 0px 20px;
    min-height: 100px; /* Increased height */
}

.expr {
    font-size: 25px; /* Bigger text */
    color: var(--color-subtext);
    min-height: 34px;
}

.result {
    font-size: 32px; /* Larger result font */
    font-weight: bold;
    color: #f0dddd; /* Bright white for clarity */
}

/* ===== KEYS ===== */
.keys {
    display: grid;
    gap: var(--gap);
    padding: 8px;
    background: var(--bg-keys);
}

.keys button {
    border: none;
    border-radius: 10px;
    padding: 14px;
    background: rgba(15, 24, 38, 0.9);
    color: inherit;
    border: 1px solid #172033;
    transition: transform 0.15s ease, background-color 0.15s ease;
}

.keys button:hover {
    background-color: #1e2b42;
    transform: scale(1.05);
}

.keys button:active {
    transform: scale(0.97);
}

.op { color: var(--color-op); }
.fn { color: var(--color-fn); }
.danger { color: var(--color-danger); }

.equals {
    background: var(--btn-equals);
    border-color: var(--btn-equals);
}

.equals:hover {
    background: #3d8a63;
}