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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 50%, #334155 100%);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    position: relative;
    overflow-x: hidden;
}

/* 背景 */
body::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: 
        radial-gradient(circle at 20% 80%, rgba(56, 189, 248, 0.05) 0%, transparent 50%),
        radial-gradient(circle at 80% 20%, rgba(71, 85, 105, 0.1) 0%, transparent 50%);
    z-index: -1;
}

.container {
    background: rgba(30, 41, 59, 0.9);
    backdrop-filter: blur(10px);
    border: 1px solid rgba(71, 85, 105, 0.2);
    border-radius: 16px;
    padding: 3rem 2.5rem;
    box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
    width: 100%;
    max-width: 400px;
    margin: 2rem;
}

.header {
    text-align: center;
    margin-bottom: 2.5rem;
}

.title {
    font-size: 2rem;
    font-weight: 600;
    color: #f8fafc;
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

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

.form-group:last-of-type {
    margin-bottom: 2rem;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 1rem;
    background: rgba(15, 23, 42, 0.7);
    border: 1px solid rgba(71, 85, 105, 0.4);
    border-radius: 8px;
    color: #f8fafc;
    font-size: 1rem;
    font-weight: 400;
    transition: all 0.2s ease;
}

input[type="text"]:focus,
input[type="password"]:focus {
    outline: none;
    border-color: #3b82f6;
    box-shadow: 0 0 0 2px rgba(59, 130, 246, 0.1);
    background: rgba(15, 23, 42, 0.9);
}

input[type="text"]::placeholder,
input[type="password"]::placeholder {
    color: #64748b;
    font-weight: 400;
}

.input-icon {
    display: none;
}

.login-button {
    width: 100%;
    padding: 1rem;
    background: #3b82f6;
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.2s ease;
}

.login-button:hover {
    background: #2563eb;
}

.login-button:active {
    background: #1d4ed8;
}

.copyright {
    margin-top: 2rem;
    text-align: center;
    color: #64748b;
    font-size: 0.8rem;
    font-weight: 400;
    opacity: 0.8;
}

.copyright a.footer-site-link {
    color: #64748b;         /* リンクの文字色をグレーに */
    text-decoration: none;  /* デフォルトの下線を削除 */
    opacity: 0.8;            /* 親と同じ透明度を設定 */
}

.copyright a.footer-site-link:hover {
    text-decoration: underline; /* ホバー時に下線を表示（任意） */
}


.error-message {
    color: #ef4444;
    font-size: 0.9rem;
    margin-top: 1rem;
    padding: 0.75rem;
    background: rgba(239, 68, 68, 0.1);
    border: 1px solid rgba(239, 68, 68, 0.2);
    border-radius: 8px;
    text-align: center;
}

/* スマートフォン対応 */
@media (max-width: 480px) {
    .container {
        padding: 2rem 1.5rem;
        margin: 1rem;
        border-radius: 12px;
    }

    .title {
        font-size: 1.75rem;
    }

    input[type="text"],
    input[type="password"] {
        padding: 0.875rem;
        font-size: 16px; /* iOS Safari のズーム防止 */
    }

    .login-button {
        padding: 0.875rem;
        font-size: 1rem;
    }

    .copyright {
        font-size: 0.75rem;
        margin-top: 1.5rem;
    }
}

/* 極小画面対応 */
@media (max-width: 320px) {
    .container {
        padding: 1.5rem 1rem;
    }

    .title {
        font-size: 1.5rem;
    }
}

/* 高解像度画面対応 */
@media (min-width: 1200px) {
    .container {
        max-width: 440px;
        padding: 3.5rem 3rem;
    }
}