/* 浮动的冰粒子 */
.snowflake {
    position: fixed;
    pointer-events: none;
    z-index: 9999;
    color: var(--ice-crystal);
    opacity: 0.6;
    animation: fall linear infinite;
}

@keyframes fall {
    0% { transform: translateY(-10vh) rotate(0deg); }
    100% { transform: translateY(110vh) rotate(360deg); }
}

/* 笨蛋按钮：带有一点冷光的扫描效果 */
.btn-cirno {
    display: inline-block;
    padding: 10px 30px;
    background: linear-gradient(45deg, var(--ice-crystal), var(--ice-deep));
    color: white;
    text-decoration: none;
    font-weight: bold;
    border-radius: 4px;
    position: relative;
    overflow: hidden;
}

.btn-cirno::after {
    content: "";
    position: absolute;
    top: -50%; left: -50%;
    width: 200%; height: 200%;
    background: linear-gradient(rgba(255,255,255,0), rgba(255,255,255,0.4), rgba(255,255,255,0));
    transform: rotate(45deg);
    transition: 0.5s;
}

.btn-cirno:hover::after {
    left: 120%;
}