CSS3 diamond puzzle realizes the function of rotating only div and not rotating the background image

<template>
    <section class="box">
        <div class="bg" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        <div v-if="item1Show" class="item item1" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        <div v-if="item2Show" class="item item2" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        <div v-if="item3Show" class="item item3" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        <div v-if="item4Show" class="item item4" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        <div v-if="item5Show" class="item item5wrap">
            <div class="item5" :style="{ backgroundImage: `url(${bgImg}) ` }"></div>
        </div>
    </section>
</template>
<script>
import bgImg from "@/assets/bg.jpeg";
export default {
    data() {
        return {
            bgImg,
            item1Show: false,
            item2Show: true,
            item3Show: true,
            item4Show: true,
            item5Show: true
        };
    }
};
</script>
<style lang="less">
@borderColor: #333;
.box {
    margin: 0px auto;
    width: 300px;
    height: 200px;
    background-color: #000;
    position: relative;
    .bg {
        width: 100%;
        height: 100%;
        position: absolute;
        left: 0;
        top: 0;
        background-position: center center;
        background-repeat: no-repeat;
        background-size: 100% 100%;
        opacity: 0.5;
    }
    .item {
        width: 50%;
        height: 50%;
        box-sizing: border-box;
        background-size: 200% 200%;
        border-right: 1px solid @borderColor;
        border-bottom: 1px solid @borderColor;
        position: absolute;
    }
    .item1 {
        background-position: 0 0;
        left: 0;
        top: 0;
    }
    .item2 {
        background-position: 100% 0;
        left: 50%;
        top: 0;
    }
    .item3 {
        background-position: 0 100%;
        left: 0;
        top: 50%;
    }
    .item4 {
        background-position: 100% 100%;
        left: 50%;
        top: 50%;
    }
    .item5wrap {
        width: 100px;
        height: 100px;
        border-left: 1px solid @borderColor;
        border-top: 1px solid @borderColor;
        transform: rotate(45deg);
        left: 50%;
        top: 50%;            
        transform: translate(-50%, -50%) rotate(45deg);
        overflow: hidden;
        .item5 {
            width: 150px;
            height: 150px;
            background-position: 50% 50%;
            background-size: 200% 133%;
            position: absolute;
            left: 50%;
            top: 50%;
            transform: translate(-50%, -50%) rotate(-45deg);
        }
    }
}
</style>