/* ========== MD3 设计变量 ========== */
:root {
    --md-sys-color-primary: #6750A4;
    --md-sys-color-on-primary: #FFFFFF;
    --md-sys-color-primary-container: #EADDFF;
    --md-sys-color-on-primary-container: #21005D;
    --md-sys-color-secondary: #625B71;
    --md-sys-color-on-secondary: #FFFFFF;
    --md-sys-color-secondary-container: #E8DEF8;
    --md-sys-color-on-secondary-container: #1D192B;
    --md-sys-color-surface: #FEF7FF;
    --md-sys-color-on-surface: #1D1B20;
    --md-sys-color-surface-variant: #E7E0EC;
    --md-sys-color-on-surface-variant: #49454F;
    --md-sys-color-outline: #79747E;
    --md-sys-color-error: #B3261E;
    --md-sys-color-on-error: #FFFFFF;
    --md-sys-color-background: #F7F2FA;

    --md-sys-shape-corner-full: 9999px;
    --md-sys-shape-corner-large: 28px;
    --md-sys-shape-corner-medium: 16px;
    --md-sys-shape-corner-small: 12px;

    --md-sys-elevation-1: 0 1px 2px rgba(0,0,0,0.05);
    --md-sys-elevation-2: 0 1px 4px rgba(0,0,0,0.05);
    --md-sys-elevation-3: 0 2px 8px rgba(0,0,0,0.07);

    --md-sys-typescale-body-medium: 14px/20px 'Roboto', sans-serif;
    --md-sys-typescale-title-large: 22px/28px 'Roboto', sans-serif;
    --md-sys-typescale-title-medium: 16px/24px 'Roboto', sans-serif;
    --md-sys-typescale-label-large: 14px/20px 'Roboto', sans-serif;
}

[data-theme="dark"] {
    --md-sys-color-primary: #D0BCFF;
    --md-sys-color-on-primary: #381E72;
    --md-sys-color-primary-container: #4F378B;
    --md-sys-color-on-primary-container: #EADDFF;
    --md-sys-color-secondary: #CCC2DC;
    --md-sys-color-on-secondary: #332D41;
    --md-sys-color-secondary-container: #4A4458;
    --md-sys-color-on-secondary-container: #E8DEF8;
    --md-sys-color-surface: #141218;
    --md-sys-color-on-surface: #E6E0E9;
    --md-sys-color-surface-variant: #49454F;
    --md-sys-color-on-surface-variant: #CAC4D0;
    --md-sys-color-outline: #938F99;
    --md-sys-color-error: #F2B8B5;
    --md-sys-color-on-error: #601410;
    --md-sys-color-background: #1D1B20;
}

* { margin: 0; padding: 0; box-sizing: border-box; }

body {
    font: var(--md-sys-typescale-body-medium);
    background: var(--md-sys-color-background);
    color: var(--md-sys-color-on-surface);
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    transition: background 0.3s, color 0.3s;
}

/* 背景启用时：覆盖且不平铺 */
body.background-enabled {
    background-size: cover;
    background-position: center;
    background-repeat: no-repeat;  /* 关键：禁止平铺 */
    background-attachment: fixed;
}

/* 登录容器 */
.login-container {
    width: 100%;
    max-width: 400px;
    padding: 20px;
}

/* 卡片 */
.login-box {
    background: rgba(255, 255, 255, 0.25);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border-radius: var(--md-sys-shape-corner-medium);
    padding: 32px;
    box-shadow: 0 2px 12px rgba(0, 0, 0, 0.06);
    border: 1px solid rgba(255, 255, 255, 0.2);
    transition: background 0.3s;
}
[data-theme="dark"] .login-box {
    background: rgba(0, 0, 0, 0.35);
    border-color: rgba(255, 255, 255, 0.08);
}

.login-box h1 {
    font: var(--md-sys-typescale-title-large);
    font-weight: 500;
    color: var(--md-sys-color-on-surface);
    text-align: center;
    margin-bottom: 24px;
}

/* 表单 */
form label {
    display: block;
    font-size: 12px;
    color: var(--md-sys-color-on-surface-variant);
    margin-bottom: 4px;
    margin-top: 16px;
}
form input {
    font: var(--md-sys-typescale-body-medium);
    width: 100%;
    padding: 10px 14px;
    border: 1px solid rgba(128, 128, 128, 0.2);
    border-radius: var(--md-sys-shape-corner-small);
    background: rgba(255, 255, 255, 0.7);
    color: var(--md-sys-color-on-surface);
    outline: none;
    transition: all 0.2s;
}
[data-theme="dark"] form input {
    background: rgba(255, 255, 255, 0.08);
    border-color: rgba(255,255,255,0.15);
}
form input:focus {
    border-color: var(--md-sys-color-primary);
    box-shadow: 0 0 0 3px rgba(103, 80, 164, 0.12);
    background: var(--md-sys-color-surface);
}

/* 按钮 */
.md-button {
    font-family: inherit;
    font-size: 13px;
    letter-spacing: 0.2px;
    border: none;
    border-radius: var(--md-sys-shape-corner-full);
    padding: 8px 16px;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 6px;
    transition: all 0.2s;
    outline: none;
    font-weight: 500;
    text-transform: none;
}
.md-button--primary {
    background: var(--md-sys-color-primary-container);
    color: var(--md-sys-color-on-primary-container);
    width: 100%;
    padding: 12px;
    margin-top: 24px;
}
.md-button--primary:hover {
    background: var(--md-sys-color-primary);
    color: var(--md-sys-color-on-primary);
    box-shadow: var(--md-sys-elevation-2);
}

/* 主题切换按钮固定右上角 */
.theme-toggle {
    position: fixed;
    top: 16px;
    right: 16px;
    z-index: 100;
    background: var(--md-sys-color-primary-container);
    color: var(--md-sys-color-on-primary-container);
    box-shadow: var(--md-sys-elevation-2);
}
.theme-toggle:hover {
    background: var(--md-sys-color-primary);
    color: var(--md-sys-color-on-primary);
}

/* 错误消息 */
.msg {
    padding: 10px 14px;
    border-radius: var(--md-sys-shape-corner-small);
    font-size: 13px;
    margin-bottom: 16px;
}
.msg.error {
    background: rgba(244, 67, 54, 0.12);
    color: #C62828;
}
[data-theme="dark"] .msg.error {
    color: #E57373;
}

/* 提示 */
.note {
    text-align: center;
    color: var(--md-sys-color-on-surface-variant);
    font-size: 12px;
    margin-top: 16px;
    opacity: 0.8;
}