:root {
    --color-bg: #ffffff;
    --color-surface: #ffffff;
    --color-border: #e5e7eb;
    --color-text: #3f3f46;
    --color-text-muted: #71717a;
    --color-primary: #3b82f6;
    --color-primary-hover: #2563eb;
    --color-danger-bg: #fef2f2;
    --color-danger-border: #fecaca;
    --color-danger-text: #991b1b;
    --color-info-bg: #eff6ff;
    --color-info-border: #bfdbfe;
    --color-info-text: #1d4ed8;
    --radius-md: 8px;
    --radius-lg: 12px;
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-5: 24px;
    --space-6: 32px;
    --shadow-1: 0 1px 2px rgba(15, 23, 42, 0.08);
    --shadow-2: 0 8px 24px rgba(15, 23, 42, 0.08);
}

*,
*::before,
*::after {
    box-sizing: border-box;
}

html {
    font-size: 16px;
}

body {
    margin: 0;
    min-height: 100vh;
    color: var(--color-text);
    background:
        linear-gradient(180deg, rgba(59, 130, 246, 0.05), rgba(59, 130, 246, 0) 220px),
        var(--color-bg);
    font-family: "Noto Sans JP", "Hiragino Sans", "Yu Gothic UI", "Yu Gothic", sans-serif;
    line-height: 1.6;
}

button,
input {
    font: inherit;
}

.container {
    width: min(100% - 32px, 440px);
    margin: 96px auto 0;
}

.card {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-lg);
    overflow: hidden;
}

.shadow {
    box-shadow: var(--shadow-2);
}

.card-body {
    padding: var(--space-6) var(--space-5);
}

.text-center {
    text-align: center;
}

.mb-3 {
    margin-bottom: var(--space-4);
}

.mb-4 {
    margin-bottom: var(--space-5);
}

.form-label {
    display: inline-block;
    margin-bottom: var(--space-2);
    font-size: 0.9375rem;
    font-weight: 700;
}

.form-control {
    width: 100%;
    min-height: 48px;
    padding: 0 var(--space-4);
    color: var(--color-text);
    background: #fff;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    outline: none;
    transition: border-color 0.14s ease, box-shadow 0.14s ease;
}

.form-control:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 4px rgba(59, 130, 246, 0.16);
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 48px;
    padding: 0 var(--space-4);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-weight: 700;
    transition: background-color 0.14s ease, border-color 0.14s ease, transform 0.14s ease;
}

.btn:hover {
    transform: translateY(-1px);
}

.btn-sm {
    min-height: 40px;
    padding: 0 var(--space-3);
    font-size: 0.875rem;
}

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

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

.btn-outline-secondary {
    color: var(--color-text);
    background: #fff;
    border-color: var(--color-border);
}

.btn-outline-secondary:hover {
    background: #f8fafc;
}

.w-100 {
    width: 100%;
}

.alert {
    padding: var(--space-3) var(--space-4);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    font-size: 0.9375rem;
}

.alert-danger {
    color: var(--color-danger-text);
    background: var(--color-danger-bg);
    border-color: var(--color-danger-border);
}

.alert-info {
    color: var(--color-info-text);
    background: var(--color-info-bg);
    border-color: var(--color-info-border);
}

@media (max-width: 640px) {
    .container {
        margin-top: 48px;
    }

    .card-body {
        padding: var(--space-5) var(--space-4);
    }
}