:root {
    /* 浅色主题 */
    --bg-color: #f2f2f7;
    --glass-bg: rgba(255, 255, 255, 0.45);
    --glass-border: rgba(255, 255, 255, 0.6);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.08);
    --text-main: #1c1c1e;
    --text-sub: #8e8e93;
    --active-bg: rgba(0, 122, 255, 0.15);
    --active-color: #007aff;
}

/* 深色主题 */
body.dark-mode {
    --bg-color: #000000;
    --glass-bg: rgba(44, 44, 46, 0.65);
    --glass-border: rgba(255, 255, 255, 0.12);
    --glass-shadow: 0 8px 32px rgba(0, 0, 0, 0.6);
    --text-main: #f2f2f7;
    --text-sub: #8e8e93;
    --active-bg: rgba(10, 132, 255, 0.25);
    --active-color: #0a84ff;
}

* { margin: 0; padding: 0; box-sizing: border-box; font-family: -apple-system, system-ui, sans-serif; }

body {
    background-color: var(--bg-color);
    background-image: radial-gradient(circle at 0% 30%, #ffd1ff 0%, #ff9a9e 40%, #a1c4fd 100%);
    background-attachment: fixed;
    background-size: cover;
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background-color 0.3s, background-image 0.3s, color 0.3s;
}
body.dark-mode {
    background-image: radial-gradient(circle at 10% 20%, #1c1c1e 0%, #000000 100%);
}

.app-container {
    width: 100%;
    max-width: 420px;
    height: 100vh;
    max-height: 900px;
    position: relative;
    display: flex;
    flex-direction: column;
    padding: 20px 20px 30px;
    overflow: hidden;
}

/* 顶部液态玻璃 */
.glass-top-bar {
    width: 100%;
    background: var(--glass-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-radius: 48px;
    border: 1px solid var(--glass-border);
    box-shadow: var(--glass-shadow);
    padding: 20px 0;
    display: flex;
    flex-direction: column;
    align-items: center;
    margin-top: 20px;
    margin-bottom: 40px;
    color: var(--text-main);
}
.top-bar-title { font-size: 24px; font-weight: 600; letter-spacing: 0.5px; }
.top-bar-sub { font-size: 13px; color: var(--text-sub); margin-top: 4px; }

/* 中间交互 */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 30px;
}

.circle-button {
    width: 150px;
    height: 150px;
    border-radius: 50%;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--glass-border);
    box-shadow: 0 12px 40px rgba(0, 0, 0, 0.08), inset 0 2px 6px rgba(255,255,255,0.6);
    display: flex;
    justify-content: center;
    align-items: center;
    cursor: grab;
    user-select: none;
    transition: transform 0.15s, box-shadow 0.15s, background 0.3s;
    color: var(--text-main);
    position: relative;
    touch-action: none;
}
.circle-button:active { transform: scale(0.92); }
.circle-button.dragging {
    opacity: 0.85;
    transform: scale(1.05);
    box-shadow: 0 0 40px rgba(0, 122, 255, 0.25);
    cursor: grabbing;
}
.circle-button svg { transition: stroke 0.3s; }

/* 底部导航 */
.glass-navbar {
    width: 100%;
    background: var(--glass-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border-radius: 48px;
    border: 1px solid var(--glass-border);
    box-shadow: var(--glass-shadow);
    padding: 14px 15px;
    display: flex;
    justify-content: space-around;
    align-items: center;
}

.nav-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 8px 16px;
    border-radius: 24px;
    cursor: pointer;
    color: var(--text-sub);
    transition: background 0.15s, color 0.15s, transform 0.1s;
    min-width: 56px;
}
.nav-item .nav-icon { line-height: 0; margin-bottom: 4px; }
.nav-item span { font-size: 10px; font-weight: 500; }

.nav-item.active {
    background: var(--active-bg);
    color: var(--active-color);
}
.nav-item.active svg { fill: var(--active-color); }

.nav-item:active { transform: scale(0.88); }
.nav-item.drag-hover {
    background: var(--active-bg);
    color: var(--active-color);
    transform: scale(1.1);
}
.nav-item.drag-hover svg { fill: var(--active-color); }