.bkbg-sc-app {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    box-sizing: border-box;
}

.bkbg-sc-app *, .bkbg-sc-app *::before, .bkbg-sc-app *::after {
    box-sizing: border-box;
}

.bkbg-sc-header {
    text-align: center;
    margin-bottom: 20px;
}

.bkbg-sc-title {
    font-family:     var(--bksc-tt-font-family, inherit);
    font-size:       var(--bksc-tt-font-size-d, 28px);
    font-weight:     var(--bksc-tt-font-weight, 700);
    font-style:      var(--bksc-tt-font-style, normal);
    text-decoration: var(--bksc-tt-text-decoration, none);
    text-transform:  var(--bksc-tt-text-transform, none);
    line-height:     var(--bksc-tt-line-height-d, 1.2);
    letter-spacing:  var(--bksc-tt-letter-spacing-d, normal);
    word-spacing:    var(--bksc-tt-word-spacing-d, normal);
    margin: 0 0 6px;
}

.bkbg-sc-subtitle {
    font-family:     var(--bksc-st-font-family, inherit);
    font-size:       var(--bksc-st-font-size-d, 15px);
    font-weight:     var(--bksc-st-font-weight, 400);
    font-style:      var(--bksc-st-font-style, normal);
    text-decoration: var(--bksc-st-text-decoration, none);
    text-transform:  var(--bksc-st-text-transform, none);
    line-height:     var(--bksc-st-line-height-d, 1.4);
    letter-spacing:  var(--bksc-st-letter-spacing-d, normal);
    word-spacing:    var(--bksc-st-word-spacing-d, normal);
    opacity: 0.7;
    margin: 0;
}

/* Calculator body */
.bkbg-sc-calc {
    background: #1a1a2e;
    border-radius: 20px;
    padding: 24px;
    max-width: 420px;
    margin: 0 auto;
    box-shadow: 0 8px 40px rgba(0, 0, 0, 0.45);
}

/* Top bar: angle mode + memory */
.bkbg-sc-topbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 8px;
    min-height: 26px;
}

.bkbg-sc-angle-toggle {
    display: flex;
    gap: 4px;
}

.bkbg-sc-angle-btn {
    padding: 3px 10px;
    border: none;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 700;
    font-size: 12px;
    font-family: inherit;
    transition: background 0.2s, color 0.2s;
}

.bkbg-sc-mem-indicator {
    font-size: 12px;
    font-weight: 700;
    color: #86efac;
    font-family: ui-monospace, monospace;
    min-height: 16px;
}

/* Expression */
.bkbg-sc-expr {
    text-align: right;
    font-size: 13px;
    color: rgba(255, 255, 255, 0.4);
    font-family: ui-monospace, 'Cascadia Code', monospace;
    min-height: 18px;
    margin-bottom: 2px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}

/* Display */
.bkbg-sc-display {
    background: #0d0d1a;
    border-radius: 10px;
    padding: 12px 16px;
    text-align: right;
    font-size: 36px;
    font-weight: 700;
    color: #ffffff;
    font-family: ui-monospace, 'Cascadia Code', monospace;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    margin-bottom: 14px;
    min-height: 64px;
    display: flex;
    align-items: center;
    justify-content: flex-end;
}

/* Button grid */
.bkbg-sc-grid {
    display: grid;
    grid-template-columns: repeat(5, 1fr);
    gap: 6px;
}

.bkbg-sc-btn {
    border: none;
    cursor: pointer;
    font-weight: 600;
    font-size: 15px;
    font-family: inherit;
    border-radius: 10px;
    min-height: 44px;
    transition: filter 0.15s, transform 0.1s;
    line-height: 1;
    padding: 0 4px;
    user-select: none;
    -webkit-user-select: none;
}

.bkbg-sc-btn:hover {
    filter: brightness(1.25);
}

.bkbg-sc-btn:active {
    transform: scale(0.94);
}

.bkbg-sc-btn-num   { background: #2d2d4a; color: #ffffff; }
.bkbg-sc-btn-op    { background: #3d2d6a; color: #c4b5fd; }
.bkbg-sc-btn-fn    { background: #1e2a4a; color: #93c5fd; }
.bkbg-sc-btn-eq    { background: #6c3fb5; color: #ffffff; }
.bkbg-sc-btn-clear { background: #7f1d1d; color: #fecaca; }
.bkbg-sc-btn-mem   { background: #1e2a4a; color: #86efac; }

/* History */
.bkbg-sc-history {
    margin-top: 16px;
    background: #111128;
    border-radius: 8px;
    padding: 10px 12px;
    max-height: 140px;
    overflow-y: auto;
}

.bkbg-sc-history-label {
    font-size: 11px;
    font-weight: 700;
    color: rgba(255, 255, 255, 0.3);
    text-transform: uppercase;
    letter-spacing: 0.05em;
    margin-bottom: 6px;
}

.bkbg-sc-history-entry {
    font-size: 13px;
    color: #9ca3af;
    font-family: ui-monospace, monospace;
    padding: 3px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    cursor: default;
}

.bkbg-sc-history-entry:last-child {
    border-bottom: none;
}

/* Keyboard hint */
.bkbg-sc-hint {
    text-align: center;
    margin-top: 10px;
    font-size: 11px;
    color: rgba(255, 255, 255, 0.25);
}

/* Responsive — Tablet */
@media (max-width: 1024px) {
    .bkbg-sc-title {
        font-size:       var(--bksc-tt-font-size-t, var(--bksc-tt-font-size-d, 28px));
        line-height:     var(--bksc-tt-line-height-t, var(--bksc-tt-line-height-d, 1.2));
        letter-spacing:  var(--bksc-tt-letter-spacing-t, var(--bksc-tt-letter-spacing-d, normal));
        word-spacing:    var(--bksc-tt-word-spacing-t, var(--bksc-tt-word-spacing-d, normal));
    }
    .bkbg-sc-subtitle {
        font-size:       var(--bksc-st-font-size-t, var(--bksc-st-font-size-d, 15px));
        line-height:     var(--bksc-st-line-height-t, var(--bksc-st-line-height-d, 1.4));
        letter-spacing:  var(--bksc-st-letter-spacing-t, var(--bksc-st-letter-spacing-d, normal));
        word-spacing:    var(--bksc-st-word-spacing-t, var(--bksc-st-word-spacing-d, normal));
    }
}

/* Responsive — Mobile */
@media (max-width: 767px) {
    .bkbg-sc-title {
        font-size:       var(--bksc-tt-font-size-m, var(--bksc-tt-font-size-t, var(--bksc-tt-font-size-d, 28px)));
        line-height:     var(--bksc-tt-line-height-m, var(--bksc-tt-line-height-t, var(--bksc-tt-line-height-d, 1.2)));
        letter-spacing:  var(--bksc-tt-letter-spacing-m, var(--bksc-tt-letter-spacing-t, var(--bksc-tt-letter-spacing-d, normal)));
        word-spacing:    var(--bksc-tt-word-spacing-m, var(--bksc-tt-word-spacing-t, var(--bksc-tt-word-spacing-d, normal)));
    }
    .bkbg-sc-subtitle {
        font-size:       var(--bksc-st-font-size-m, var(--bksc-st-font-size-t, var(--bksc-st-font-size-d, 15px)));
        line-height:     var(--bksc-st-line-height-m, var(--bksc-st-line-height-t, var(--bksc-st-line-height-d, 1.4)));
        letter-spacing:  var(--bksc-st-letter-spacing-m, var(--bksc-st-letter-spacing-t, var(--bksc-st-letter-spacing-d, normal)));
        word-spacing:    var(--bksc-st-word-spacing-m, var(--bksc-st-word-spacing-t, var(--bksc-st-word-spacing-d, normal)));
    }
}