/* ===== 基础样式 ===== */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    /* 科技蓝 + 活力绿配色方案 */
    --primary-color: #3B82F6;
    --primary-hover: #2563EB;
    --secondary-color: #10B981;
    --accent-color: #34D399;
    --gradient-primary: linear-gradient(135deg, #3B82F6 0%, #10B981 100%);
    --gradient-light: linear-gradient(135deg, #DBEAFE 0%, #D1FAE5 100%);
    --bg-color: #F8FAFC;
    --card-bg: #ffffff;
    --text-primary: #1F2937;
    --text-secondary: #6B7280;
    --border-color: #E5E7EB;
    --shadow-sm: 0 4px 15px rgba(59, 130, 246, 0.08);
    --shadow-md: 0 8px 30px rgba(59, 130, 246, 0.12);
    --shadow-lg: 0 20px 50px rgba(59, 130, 246, 0.18);
    --radius-sm: 12px;
    --radius-md: 16px;
    --radius-lg: 24px;
    --sidebar-width: 240px;
    --top-nav-height: 60px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    background: linear-gradient(180deg, #EFF6FF 0%, #F0FDF4 50%, #F8FAFC 100%);
    background-attachment: fixed;
    color: var(--text-primary);
    line-height: 1.6;
}

a {
    text-decoration: none;
    color: inherit;
}

button {
    cursor: pointer;
    border: none;
    outline: none;
    font-family: inherit;
}

/* ===== 顶部导航栏 ===== */
.top-nav {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--top-nav-height);
    background: var(--card-bg);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 20px;
    z-index: 1000;
}

.nav-left {
    display: flex;
    align-items: center;
    gap: 15px;
}

.menu-toggle {
    background: none;
    font-size: 20px;
    color: var(--text-secondary);
    padding: 8px;
    border-radius: var(--radius-sm);
    transition: all 0.3s;
}

.menu-toggle:hover {
    background: linear-gradient(135deg, #DBEAFE 0%, #D1FAE5 100%);
    color: var(--primary-color);
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 20px;
    font-weight: 700;
    color: var(--primary-color);
}

.logo i {
    font-size: 28px;
}

.nav-center {
    flex: 1;
    max-width: 500px;
    margin: 0 20px;
}

.search-box {
    position: relative;
}

.search-box i {
    position: absolute;
    left: 15px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-secondary);
}

.search-box input {
    width: 100%;
    padding: 10px 15px 10px 40px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    background: var(--card-bg);
    font-size: 14px;
    transition: all 0.3s;
}

.search-box input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.1);
}

.nav-right {
    display: flex;
    align-items: center;
    gap: 15px;
}

.btn-publish {
    display: flex;
    align-items: center;
    gap: 6px;
    background: var(--gradient-primary);
    color: white;
    padding: 10px 20px;
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.3);
}

.btn-publish:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(59, 130, 246, 0.4);
}

.nav-icons {
    display: flex;
    align-items: center;
    gap: 10px;
}

.icon-btn {
    position: relative;
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: var(--radius-sm);
    color: var(--text-secondary);
    font-size: 18px;
    transition: all 0.3s;
}

.icon-btn:hover {
    background: linear-gradient(135deg, #DBEAFE 0%, #D1FAE5 100%);
    color: var(--primary-color);
}

.icon-btn .badge {
    position: absolute;
    top: 5px;
    right: 5px;
    background: var(--gradient-primary);
    color: white;
    font-size: 10px;
    padding: 2px 6px;
    border-radius: 10px;
    font-weight: 600;
}

.user-menu {
    position: relative;
}

.user-menu .avatar {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    cursor: pointer;
    object-fit: cover;
    border: 3px solid transparent;
    background: linear-gradient(white, white) padding-box,
                var(--gradient-primary) border-box;
    transition: all 0.3s;
}

.user-menu .avatar:hover {
    transform: scale(1.05);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.25);
}

.user-menu .dropdown {
    position: absolute;
    top: 55px;
    right: 0;
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    min-width: 180px;
    padding: 10px 0;
    z-index: 1001;
}

.user-menu .dropdown a {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px 20px;
    font-size: 14px;
    color: var(--text-primary);
    transition: all 0.3s;
}

.user-menu .dropdown a:hover {
    background: linear-gradient(90deg, #DBEAFE 0%, transparent 100%);
    color: var(--primary-color);
}

.user-menu .dropdown a i {
    color: var(--primary-color);
}

.user-menu .dropdown hr {
    border: none;
    border-top: 1px solid var(--border-color);
    margin: 10px 15px;
}

/* ===== 侧边栏 ===== */
.sidebar {
    position: fixed;
    top: var(--top-nav-height);
    left: 0;
    width: var(--sidebar-width);
    height: calc(100vh - var(--top-nav-height));
    background: var(--card-bg);
    border-right: 1px solid var(--border-color);
    overflow-y: auto;
    z-index: 999;
    transition: transform 0.3s;
}

.sidebar.collapsed {
    transform: translateX(-100%);
}

.sidebar-nav {
    padding: 15px 10px;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 18px;
    border-radius: var(--radius-md);
    color: var(--text-secondary);
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 6px;
    transition: all 0.3s;
}

.nav-item:hover {
    background: linear-gradient(135deg, #DBEAFE 0%, #D1FAE5 100%);
    color: var(--primary-color);
}

.nav-item.active {
    background: var(--gradient-primary);
    color: white;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.nav-item i {
    font-size: 18px;
    width: 24px;
    text-align: center;
}

.nav-divider {
    height: 1px;
    background: var(--border-color);
    margin: 12px 0;
}

/* ===== 主内容区 ===== */
.main-content {
    margin-left: var(--sidebar-width);
    margin-top: var(--top-nav-height);
    padding: 30px;
    min-height: calc(100vh - var(--top-nav-height));
    transition: margin-left 0.3s;
    background: linear-gradient(180deg, #EFF6FF 0%, #F0FDF4 50%, #F8FAFC 100%);
    background-attachment: fixed;
}

/* 页面没有侧边栏时的主内容区 */
.create-main,
.profile-main,
.friends-main,
.messages-main,
.groups-main {
    margin-top: var(--top-nav-height);
    min-height: calc(100vh - var(--top-nav-height));
    background: linear-gradient(180deg, #EFF6FF 0%, #F0FDF4 50%, #F8FAFC 100%);
    background-attachment: fixed;
}

.sidebar.collapsed + .main-content {
    margin-left: 0;
}

/* ===== 筛选栏 ===== */
.filter-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
}

.filter-tabs {
    display: flex;
    gap: 10px;
}

.filter-tab {
    padding: 10px 20px;
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    transition: all 0.3s;
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}

.filter-tab:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(59, 130, 246, 0.15);
}

.filter-tab.active {
    background: var(--gradient-primary);
    border-color: transparent;
    color: white;
    box-shadow: 0 4px 15px rgba(59, 130, 246, 0.3);
}

.sort-dropdown select {
    padding: 8px 16px;
    border: 1px solid var(--border-color);
    border-radius: 8px;
    background: var(--card-bg);
    font-size: 14px;
    cursor: pointer;
}

/* ===== Banner轮播 ===== */
.banner-carousel {
    position: relative;
    height: 180px;
    border-radius: 16px;
    overflow: hidden;
    margin-bottom: 20px;
}

.banner-slide {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transition: opacity 0.5s;
}

.banner-slide.active {
    opacity: 1;
}

.banner-content {
    text-align: center;
    color: white;
    padding: 20px;
}

.banner-content h2 {
    font-size: 28px;
    margin-bottom: 10px;
}

.banner-content p {
    font-size: 16px;
    opacity: 0.9;
}

/* ===== 项目瀑布流 ===== */
.projects-waterfall {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.project-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    overflow: hidden;
    box-shadow: var(--shadow-sm);
    transition: all 0.4s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
    border: 1px solid rgba(59, 130, 246, 0.06);
}

.project-card:hover {
    transform: translateY(-8px);
    box-shadow: var(--shadow-lg);
    border-color: rgba(59, 130, 246, 0.12);
}

.project-cover {
    position: relative;
    padding-top: 100%;
    overflow: hidden;
}

.project-cover img {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    object-fit: cover;
    transition: transform 0.3s;
}

.project-card:hover .project-cover img {
    transform: scale(1.05);
}

.project-type-tag {
    position: absolute;
    top: 10px;
    left: 10px;
    padding: 6px 14px;
    border-radius: 20px;
    font-size: 12px;
    font-weight: 600;
    color: white;
    box-shadow: 0 4px 10px rgba(0,0,0,0.1);
}

.project-type-tag.funding {
    background: linear-gradient(135deg, #3B82F6 0%, #2563EB 100%);
}

.project-type-tag.tech {
    background: linear-gradient(135deg, #10B981 0%, #059669 100%);
}

.project-type-tag.space {
    background: linear-gradient(135deg, #8B5CF6 0%, #7C3AED 100%);
}

.project-type-tag.hr {
    background: linear-gradient(135deg, #F59E0B 0%, #D97706 100%);
}

.project-info {
    padding: 15px;
}

.project-title {
    font-size: 16px;
    font-weight: 600;
    line-height: 1.4;
    margin-bottom: 8px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.project-summary {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.5;
    margin-bottom: 12px;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
}

.project-author {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 12px;
}

.project-author img {
    width: 24px;
    height: 24px;
    border-radius: 50%;
    object-fit: cover;
}

.project-author span {
    font-size: 13px;
    color: var(--text-secondary);
}

.project-progress {
    margin-bottom: 12px;
}

.progress-bar {
    height: 6px;
    background: var(--bg-color);
    border-radius: 3px;
    overflow: hidden;
    margin-bottom: 6px;
}

.progress-fill {
    height: 100%;
    background: var(--gradient-primary);
    border-radius: 3px;
    transition: width 0.3s;
}

.progress-info {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    color: var(--text-secondary);
}

.progress-info .percent {
    color: var(--primary-color);
    font-weight: 600;
}

.project-stats {
    display: flex;
    gap: 16px;
    padding-top: 12px;
    border-top: 1px solid var(--border-color);
}

.project-stats span {
    font-size: 13px;
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    gap: 4px;
}

/* ===== 加载更多 ===== */
.load-more {
    text-align: center;
    padding: 40px 0;
}

.load-more button {
    padding: 14px 48px;
    background: var(--card-bg);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 14px;
    font-weight: 600;
    color: var(--text-secondary);
    transition: all 0.3s;
    box-shadow: 0 4px 12px rgba(0,0,0,0.05);
}

.load-more button:hover {
    border-color: var(--primary-color);
    color: var(--primary-color);
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.15);
}

/* ===== 弹窗 ===== */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: rgba(0,0,0,0.5);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

.modal-content {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 420px;
    overflow: hidden;
    animation: modalSlide 0.3s;
    box-shadow: var(--shadow-lg);
}

@keyframes modalSlide {
    from {
        opacity: 0;
        transform: translateY(-30px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 20px 20px 0;
}

.modal-header h3 {
    font-size: 20px;
}

.close-btn {
    background: none;
    font-size: 24px;
    color: var(--text-secondary);
    padding: 4px;
}

.modal-body {
    padding: 20px;
}

/* ===== 认证表单 ===== */
.auth-tabs {
    display: flex;
    gap: 20px;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.auth-tab {
    padding: 10px 0;
    background: none;
    font-size: 16px;
    color: var(--text-secondary);
    position: relative;
}

.auth-tab.active {
    color: var(--primary-color);
    font-weight: 700;
}

.auth-tab.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--gradient-primary);
    border-radius: 3px 3px 0 0;
}

.auth-form .form-group {
    margin-bottom: 16px;
}

.auth-form input {
    width: 100%;
    padding: 14px 18px;
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    font-size: 15px;
    transition: all 0.3s;
    background: var(--bg-color);
}

.auth-form input:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.1);
    background: var(--card-bg);
}

.auth-form .checkbox label {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    font-size: 13px;
    color: var(--text-secondary);
}

.auth-form .checkbox input {
    width: auto;
    margin-top: 3px;
}

.auth-form .checkbox a {
    color: var(--primary-color);
}

.btn-primary {
    width: 100%;
    padding: 16px;
    background: var(--gradient-primary);
    color: white;
    border-radius: var(--radius-md);
    font-size: 16px;
    font-weight: 600;
    transition: all 0.3s;
    box-shadow: 0 6px 20px rgba(59, 130, 246, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(59, 130, 246, 0.4);
}

/* ===== 响应式 ===== */
@media (max-width: 768px) {
    .sidebar {
        transform: translateX(-100%);
    }

    .sidebar.open {
        transform: translateX(0);
    }

    .main-content {
        margin-left: 0;
    }

    .nav-center {
        display: none;
    }

    .btn-publish span {
        display: none;
    }

    .projects-waterfall {
        grid-template-columns: repeat(2, 1fr);
        gap: 12px;
    }
}

@media (max-width: 480px) {
    .projects-waterfall {
        grid-template-columns: 1fr;
    }
}