html - 仅在 CSS 和 HTML 中复制图像

Question

对于代码测验，我尝试仅使用 CSS 和 HTML 复制附加的图像。渐变和边框似乎效果很好，但我无法让色带边缘看起来弯曲。

这是我的标记：

<div class="container">
<div class="ribbon-wrapper-green"><div class="ribbon-green">AWESOME!</div></div>
<div class="ribbon-bottom-left"></div>
<div class="bottom-left-gradient"></div>

这是我的CSS：

    .container {
    width:300px;
    height:300px;
    margin-left:auto;
    margin-right:auto;
    margin-top:10px;
    position:relative;
    border:#CCC 1px solid;
    background-color:#EBEBEB;
    box-shadow:1px 1px 1px #CCC;
}

.ribbon-wrapper-green {
    width: 290px;
    height: 290px;
    overflow: hidden;
    position: absolute;
    top: -3px;
    right: -3px;
}

.ribbon-green {
    font: 25px Arial;
    text-align: center;
    text-shadow:0px 0px 6px #000;
    -webkit-transform: rotate(45deg);
    -moz-transform:    rotate(45deg);
    -ms-transform:     rotate(45deg);
    -o-transform:      rotate(45deg);
    position: relative;
    padding: 20px 0;
    left: 7px;
    top: 66px;
    width: 363px;
    background-color: #BFDC7A;
    background-image: -webkit-gradient(linear, left top, left bottom, from(#BFDC7A), to(#8EBF45)); 
    background-image: -webkit-linear-gradient(top, #BFDC7A, #8EBF45); 
    background-image:    -moz-linear-gradient(top, #BFDC7A, #8EBF45); 
    background-image:     -ms-linear-gradient(top, #BFDC7A, #8EBF45); 
    background-image:      -o-linear-gradient(top, #BFDC7A, #8EBF45); 
    color: #FFF;
    -webkit-box-shadow: 0px 8px 20px rgba(0,0,0,0.3);
    -moz-box-shadow:    0px 8px 20px rgba(0,0,0,0.3);
    box-shadow:         0px 8px 20px rgba(0,0,0,0.3);
}

.ribbon-green:before, .ribbon-green:after {
    content: "";
    border-top:   4px solid #6e8900;   
    border-left:  4px solid transparent;
    border-right: 4px solid transparent;
    position:absolute;
    bottom: -4px;
}

.ribbon-green:before {
    left: 0;
}

.ribbon-green:after {
    right: 0;
}

.ribbon-bottom-left {
    width: 0px;
    height: 0px;
    border-style: solid;
    border-width: 250px 0 0 250px;
    border-color: transparent transparent transparent #D32023;
    position:absolute;
    bottom:-5px;
    left:-5px;
    border-top-left-radius:10px;
    border-bottom-right-radius:10px;
    -moz-border-radius-topleft:10px;
    -moz-border-radius-bottomright:10px;
    z-index:1;
}

.bottom-left-gradient {
    position:absolute;
    bottom:-8px;
    left:-8px;
    z-index:100;
    height:245px;
    width:245px;
    opacity:0.4;
    filter:alpha(opacity=40);
    background: -moz-linear-gradient(45deg,  rgba(255,255,255,1) 0%, rgba(255,255,255,0.92) 4%, rgba(255,255,255,0) 51%); /* FF3.6+ */
    background: -webkit-gradient(linear, left bottom, right top, color-stop(0%,rgba(255,255,255,1)), color-stop(4%,rgba(255,255,255,0.92)), color-stop(51%,rgba(255,255,255,0))); /* Chrome,Safari4+ */
    background: -webkit-linear-gradient(45deg,  rgba(255,255,255,1) 0%,rgba(255,255,255,0.92) 4%,rgba(255,255,255,0) 51%); /* Chrome10+,Safari5.1+ */
    background: -o-linear-gradient(45deg,  rgba(255,255,255,1) 0%,rgba(255,255,255,0.92) 4%,rgba(255,255,255,0) 51%); /* Opera 11.10+ */
    background: -ms-linear-gradient(45deg,  rgba(255,255,255,1) 0%,rgba(255,255,255,0.92) 4%,rgba(255,255,255,0) 51%); /* IE10+ */
    background: linear-gradient(45deg,  rgba(255,255,255,1) 0%,rgba(255,255,255,0.92) 4%,rgba(255,255,255,0) 51%); /* W3C */
    filter: progid:DXImageTransform.Microsoft.gradient( startColorstr='#ffffff', endColorstr='#00ffffff',GradientType=1 ); /* IE6-9 fallback on horizontal gradient */
    border-style:solid;
    border-width:0 0 5px 5px;
    border-radius:10px;
    -moz-border-radius:10px;
    border-color:#E41316;
}

图像在这里像这个例子一样出来：http: //arunsood.me/code-quizzes/placebo-effect/。

我需要复制的原件如下。如何仅通过 CSS 实现边缘弯曲效果？