body {
    font-family: 'Helvetica Neue', Arial, sans-serif;
    background-color: #eef2f3;
    color: #333;
    padding: 40px 20px;
    margin: 0;
}

.container {
    background-color: #fff;
    border-radius: 12px;
    box-shadow: 0 4px 12px rgba(0,0,0,0.08);
    max-width: 550px;
    margin: 0 auto;
    padding: 30px;
}

.nav-header {
    text-align: left;
    margin-bottom: 15px;
}

.back-link {
    color: #888;
    text-decoration: none;
    font-size: 14px;
    font-weight: bold;
    transition: color 0.2s;
}

.back-link:hover {
    color: #d9534f;
}

h1 { 
    color: #d9534f; 
    text-align: center; 
    margin-top: 0;
    font-size: 26px;
}

.form-group {
    margin-bottom: 15px;
}

input, textarea {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 8px;
    box-sizing: border-box;
    font-size: 14px;
    background-color: #fdfdfd;
    transition: border-color 0.2s;
}

input:focus, textarea:focus {
    border-color: #d9534f;
    outline: none;
}

textarea {
    height: 70px;
    resize: none;
}

button {
    width: 100%;
    padding: 12px;
    background-color: #d9534f;
    color: white;
    border: none;
    border-radius: 8px;
    font-weight: bold;
    font-size: 16px;
    cursor: pointer;
    transition: background 0.2s;
}

button:hover {
    background-color: #c9302c;
}

.timeline-title {
    margin-top: 35px;
    font-size: 16px;
    color: #555;
    border-bottom: 2px solid #f4f7f6;
    padding-bottom: 5px;
}

/* 💬 投稿メッセージ一個一個の箱 */
.post {
    background-color: #f9f9f9;
    padding: 15px;
    border-radius: 8px;
    margin-bottom: 12px;
    border-left: 5px solid #d9534f;
    text-align: left;
    box-shadow: 0 1px 3px rgba(0,0,0,0.02);
}

.post-header {
    display: flex;
    justify-content: space-between;
    font-size: 12px;
    margin-bottom: 5px;
}

.post-user {
    font-weight: bold;
    color: #d9534f;
}

.post-time {
    color: #aaa;
}

.post-text {
    font-size: 14px;
    line-height: 1.5;
    white-space: pre-wrap; /* 改行をそのまま反映 */
}

.system-msg {
    text-align: center;
    color: #bbb;
    font-size: 12px;
    margin-top: 20px;
}