#main_bg {
    background-image: url(../assets/images/background/miku_night.webp);
    background-size: cover;
    background-repeat: no-repeat;
    background-position: center;
    position: fixed;
    min-height: 100vh;
    width: 100%;
    z-index: -1;
}

#panel {
    font-family: var(--app-font-serif);
    backdrop-filter: blur(2px);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

.b64-head {
    background: linear-gradient(135deg, var(--app-glass-strong), rgba(240, 255, 249, 0.72));
    border: 1px solid var(--app-line);
    border-radius: 14px;
    padding: 8px 14px;
    margin-bottom: 6px;
    box-shadow: var(--app-shadow-card);
    flex-shrink: 0;
}

.b64-head h1 {
    font-size: 18px;
    color: var(--app-text-heading);
    margin-bottom: 2px;
    letter-spacing: .4px;
}

.b64-head p {
    font-size: 12px;
    color: var(--app-muted);
}

.b64-tabs {
    display: flex;
    gap: 6px;
    flex-shrink: 0;
    margin-bottom: 6px;
}

.b64-tab {
    border: 1px solid var(--app-line);
    border-radius: 10px;
    padding: 8px 16px;
    background: var(--app-glass);
    color: var(--app-muted);
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    font-family: var(--app-font-serif);
    transition: border-color .18s var(--app-ease), background .18s var(--app-ease), color .18s var(--app-ease), box-shadow .18s var(--app-ease);
}

.b64-tab:hover {
    border-color: var(--app-line-strong);
    color: var(--app-text);
}

.b64-tab.is-active {
    background: linear-gradient(135deg, var(--app-accent-strong), var(--app-accent));
    border-color: transparent;
    color: var(--app-text-inverse);
    box-shadow: var(--app-accent-glow);
}

.b64-layout {
    flex: 1;
    min-height: 0;
}

.b64-pane {
    display: none;
    height: 100%;
    min-height: 0;
    grid-template-columns: 340px minmax(0, 1fr);
    gap: 8px;
}

.b64-pane.is-active {
    display: grid;
}

.b64-pane > div {
    width: 100%;
    min-height: 0;
    min-width: 0;
    background: var(--app-glass);
    border: 1px solid var(--app-line);
    border-radius: 14px;
    padding: 10px;
    box-shadow: var(--app-shadow-card);
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    gap: 8px;
    overflow-y: auto;
}

.b64-dropzone {
    position: relative;
    flex-shrink: 0;
    aspect-ratio: 1 / 1;
    max-height: 300px;
    border: 1px dashed var(--app-line-strong);
    border-radius: 12px;
    background: var(--app-overlay-dark);
    display: grid;
    place-items: center;
    cursor: pointer;
    overflow: hidden;
}

.b64-dropzone span {
    font-size: 12px;
    color: var(--app-text-inverse);
    padding: 6px 12px;
    border-radius: 999px;
    background: rgba(0, 0, 0, 0.5);
    border: 1px solid rgba(255, 255, 255, 0.15);
    text-align: center;
    line-height: 1.4;
    z-index: 1;
}

.b64-dropzone.dragover {
    border-color: var(--app-accent);
    box-shadow: 0 0 0 2px var(--app-accent-glow) inset;
}

.b64-preview {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    object-fit: contain;
    background: var(--app-overlay-dark);
    border-radius: 11px;
}

.b64-preview-lg {
    position: static;
}

.b64-dropzone input[type="file"],
.b64-pane input[type="file"] { display: none; }

.b64-stats {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 6px;
    flex-shrink: 0;
}

.b64-stat {
    background: var(--app-card);
    border: 1px solid var(--app-line-subtle);
    border-radius: 9px;
    padding: 6px 8px;
    display: flex;
    flex-direction: column;
    gap: 2px;
}

.b64-stat b {
    font-size: 11px;
    color: var(--app-muted);
    font-weight: 600;
}

.b64-stat span {
    font-size: 12px;
    color: var(--app-text);
    font-family: var(--app-font-mono);
    word-break: break-all;
}

.b64-textarea {
    flex: 1;
    min-height: 120px;
    resize: vertical;
    border: 1px solid var(--app-line);
    border-radius: 10px;
    padding: 10px 12px;
    background: var(--app-surface-input);
    font-size: 12px;
    color: var(--app-text);
    font-family: var(--app-font-mono);
    line-height: 1.55;
    box-sizing: border-box;
    transition: border-color .18s var(--app-ease), box-shadow .18s var(--app-ease);
}

.b64-textarea:focus {
    outline: none;
    border-color: var(--app-accent);
    box-shadow: 0 0 0 2px var(--app-accent-glow);
}

.b64-actions {
    display: flex;
    align-items: center;
    gap: 8px;
    flex-wrap: wrap;
    flex-shrink: 0;
}

.b64-btn {
    border: none;
    background: linear-gradient(135deg, var(--app-accent-strong), var(--app-accent));
    color: var(--app-text-inverse);
    cursor: pointer;
    padding: 9px 16px;
    font-weight: 600;
    font-size: 12px;
    border-radius: 9px;
    font-family: var(--app-font-serif);
    transition: border-color .18s var(--app-ease), box-shadow .18s var(--app-ease), transform .18s var(--app-ease), opacity .18s var(--app-ease);
}

.b64-btn:hover:not(:disabled) {
    transform: translateY(-1px);
    box-shadow: var(--app-accent-glow);
}

.b64-btn:disabled {
    opacity: 0.45;
    cursor: not-allowed;
}

.b64-btn-ghost {
    background: var(--app-glass-strong);
    border: 1px solid var(--app-line);
    color: var(--app-text);
    font-weight: 500;
}

.b64-btn-ghost:hover:not(:disabled) {
    border-color: var(--app-line-strong);
    box-shadow: none;
}

.b64-status {
    font-size: 12px;
    color: var(--app-muted);
    flex-shrink: 0;
    min-height: 16px;
    line-height: 1.5;
}

.b64-status.is-error {
    color: var(--app-error);
}

.b64-status.is-success {
    color: var(--app-success);
}

.b64-preview-box {
    flex: 1;
    min-height: 0;
    background: var(--app-glass-strong);
    border: 1px solid var(--app-line);
    border-radius: var(--app-radius-md);
    padding: 8px;
    display: block;
    overflow: auto;
    position: relative;
}

/* 默认按原始尺寸显示，超出容器滚动查看；小图则居中 */
.b64-preview-box .b64-preview {
    position: static;
    width: auto;
    height: auto;
    max-width: none;
    max-height: none;
    display: block;
    margin: auto;
    border-radius: 8px;
}

/* 若图片小于容器，回退为等比缩放充满容器，避免小图显示过小 */
.b64-preview-box .b64-preview.fit {
    width: 100%;
    height: 100%;
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

.b64-preview-empty {
    font-size: 12px;
    color: var(--app-muted);
}

@media (max-width: 1000px) {
    .b64-pane {
        grid-template-columns: 1fr;
    }

    .b64-pane > div {
        max-height: none;
    }
}

@media (max-width: 520px) {
    .b64-tabs {
        flex-direction: column;
    }
}