:root {
    --primary: #fff;
    --bg-color: rgba(5,53,61);
    --bg-envelope: #f5edd1;
    --envelope-tab: #ecdeb8;
    --envelope-cover: #e6cfa7;
    --shadow-color: rgba(0,0,0,0.2);
    --txt-color: #444;
    --heart-color: rgba(252,8,231);
}
body {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    background: var(--bg-color);
    display: flex;
    align-items: center;
    justify-content: center;
}
.container {
    height: 100vh;
    display: grid;
    place-items: center;
}
.envelope-wrapper {
    background: var(--bg-envelope);
    box-shadow: 0 0 40px var(--shadow-color);
}
.envelope {
    position: relative;
    width: 300px;
    height: 230px;
}
.envelope::before {
    content: '';
    position: absolute;
    z-index: 2;
    border-top: 130px solid var(--envelope-tab);
    border-right: 150px solid transparent;
    border-left: 150px solid transparent;
    top: 0;
    transform-origin: top;
    transition: all 0.5s ease-in-out 0.7s;
}
.envelope::after {
    content: '';
    position: absolute;
    z-index: 2;
    border-top: 130px solid transparent;
    border-right: 150px solid var(--envelope-cover);
    border-left: 150px solid var(--envelope-cover);
    border-bottom: 100px solid var(--envelope-cover);
    bottom: 0;
}
.letter {
    position: absolute;
    right: 20%;
    bottom: 0;
    width: 54%;
    height: 80%;
    background: var(--primary);
    transition: all 1s ease-in-out;
    padding: 20px 10px;
    box-shadow: 0 0 10px var(--shadow-color);
}
.text {
    font-family: 'Franklin Gothic Medium', 'Arial Narrow', Arial, sans-serif;
    font-size: 10px;
    color: var(--txt-color);
    text-align: left;
}
.heart {
    position: absolute;
    top: 50%;
    left: 50%;
    width: 15px;
    height: 15px;
    background: var(--heart-color);
    z-index: 4;
    transform: translate(-50%,-20%) rotate(45deg);
    transition: tranform 0.5s ease-in-out 1s;
    box-shadow: 0 0 10px var(--shadow-color);
    cursor: pointer;
}
.heart::before,
.heart::after {
    content: '';
    position: absolute;
    width: 15px;
    height: 15px;
    background: var(--heart-color);
    border-radius: 50%;
}
.heart::before {
    top: -7.5px;
}
.heart::after {
    right: 7.5px;
}
.flap .envelope::before {
    z-index: 0;
    transform: translateX(180deg);
}
.flap .envelope .letter {
    bottom: 100px;
    transform: scale(1.5);
    transition-delay: 1s;
}
.flap .heart {
    transform: rotate(90deg);
    transition-delay: 0.4s;
    
}