:root {
    --primary-color: #2563eb;
    --primary-hover: #1d4ed8;
    --bg-color: #f8fafc;
    --text-color: #1e293b;
    --text-muted: #64748b;
    --white: #ffffff;
    --border-color: #e2e8f0;
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1), 0 2px 4px -2px rgb(0 0 0 / 0.1);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    line-height: 1.6;
}

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 0 20px;
}

header {
    background-color: var(--white);
    border-bottom: 1px solid var(--border-color);
    padding: 1rem 0;
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-flex {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: 6px;
    cursor: pointer;
    font-weight: 600;
    transition: background 0.2s;
}

.btn-primary:hover {
    background-color: var(--primary-hover);
}

main {
    padding: 2rem 0;
}

/* Post List */
.posts-grid {
    display: grid;
    gap: 1.5rem;
}

.post-card {
    background: var(--white);
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow);
    cursor: pointer;
    transition: transform 0.2s;
}

.post-card:hover {
    transform: translateY(-4px);
}

.post-card h2 {
    margin-bottom: 0.5rem;
    color: var(--text-color);
}

.post-card p {
    color: var(--text-muted);
    overflow: hidden;
    display: -webkit-box;
    -webkit-line-clamp: 3;
    -webkit-box-orient: vertical;
}

/* Post Detail */
.post-detail h1 {
    font-size: 2.5rem;
    margin-bottom: 1rem;
}

.post-detail .meta {
    color: var(--text-muted);
    margin-bottom: 2rem;
    font-size: 0.9rem;
}

.post-detail .content {
    font-size: 1.1rem;
    white-space: pre-wrap;
}

.back-link {
    display: inline-block;
    margin-bottom: 1rem;
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
}

/* Modal */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0,0,0,0.5);
    backdrop-filter: blur(4px);
}

.modal-content {
    background-color: var(--white);
    margin: 5% auto;
    padding: 2rem;
    border-radius: 12px;
    width: 90%;
    max-width: 600px;
    position: relative;
}

.close-btn {
    position: absolute;
    right: 20px;
    top: 15px;
    font-size: 24px;
    cursor: pointer;
    color: var(--text-muted);
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 500;
}

.form-group input, .form-group textarea {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    font-family: inherit;
    font-size: 1rem;
}

#post-form .btn-primary {
    width: 100%;
    padding: 0.75rem;
    font-size: 1.1rem;
}