html, body {
    margin: 0;
    height: 100%;
    background: #1b2030;
    overflow: hidden;
    font-family: "Segoe UI", system-ui, "Microsoft YaHei", sans-serif;
    color: #e8edf6;
}

/* ── 初始界面：全屏拖放区 ─────────────────────────────────────────────── */

.drop-screen {
    position: fixed;
    inset: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    background: #0a0e18;
    transition: background .15s;
}

body.dragging .drop-screen {
    background: #101b33;
}

.drop {
    max-width: 430px;
    text-align: center;
    padding: 46px 44px;
    border: 2px dashed #2c3a57;
    border-radius: 16px;
    background: rgba(20, 26, 40, 0.5);
    transition: border-color .15s;
}

body.dragging .drop {
    border-color: #5b8def;
}

.ring {
    width: 84px;
    height: 84px;
    margin: 0 auto 22px;
    border-radius: 50%;
    background: rgba(91, 141, 239, 0.12);
    display: flex;
    align-items: center;
    justify-content: center;
}

.drop h3 {
    margin: 0 0 10px;
    font-size: 22px;
    font-weight: 600;
    letter-spacing: 0.2px;
}

.drop p {
    margin: 0;
    color: #8fa3c7;
    font-size: 13px;
    line-height: 1.65;
}

.pick {
    color: #5b8def;
    cursor: pointer;
    text-decoration: underline;
}

/* ── 3D 查看界面 ─────────────────────────────────────────────────────── */

.layout {
    position: fixed;
    inset: 0;
}

#board-canvas {
    position: absolute;
    inset: 0;
    width: 100%;
    height: 100%;
    display: block;
    touch-action: none;
}

/* 左右面板：等宽、贴顶 */
.panel {
    position: fixed;
    top: 12px;
    z-index: 10;
    width: 220px;
    max-height: calc(100vh - 24px);
    overflow-y: auto;
    padding: 12px 14px;
    background: rgba(20, 26, 40, 0.86);
    border: 1px solid #33405c;
    border-radius: 10px;
    backdrop-filter: blur(6px);
    box-shadow: 0 6px 24px rgba(0, 0, 0, 0.4);
}

.panel.left  { left: 12px; }
.panel.right { right: 12px; }

.panel h1 {
    font-size: 13px;
    margin: 0 0 8px;
    font-weight: 600;
    letter-spacing: 0.3px;
    color: #9fb4d8;
}

.status {
    font-size: 11px;
    color: #6b7da0;
    margin: 4px 0 6px;
}

.drop .status {
    margin: 14px 0 0;
    min-height: 1em;
}

.sec {
    margin-top: 8px;
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.6px;
    color: #6b7da0;
}

.row {
    display: flex;
    align-items: center;
    gap: 7px;
    padding: 2px 0;
    font-size: 13px;
    cursor: pointer;
    user-select: none;
}

.row input {
    accent-color: #5b8def;
    width: 14px;
    height: 14px;
}

/* 右侧面板的导出按钮 */
.btn {
    display: block;
    width: 100%;
    margin-top: 10px;
    padding: 8px 10px;
    background: #26314a;
    color: #e8edf6;
    border: 1px solid #3b4a69;
    border-radius: 6px;
    font-size: 13px;
    cursor: pointer;
    transition: background .12s;
}

.btn:hover {
    background: #2f3d5c;
}

.btn:active {
    background: #22304c;
}

/* 拖放悬停提示（查看界面下也接受拖放新文件） */
body.dragging::after {
    content: "";
    position: fixed;
    inset: 0;
    z-index: 99;
    border: 3px dashed #5b8def;
    border-radius: 8px;
    background: rgba(16, 27, 51, 0.35);
    pointer-events: none;
}

.hint {
    position: fixed;
    bottom: 10px;
    left: 0;
    width: 100%;
    text-align: center;
    font-size: 12px;
    color: #6b7da0;
    pointer-events: none;
}