:root {
    --bg: #f5f7fb;
    --card: #ffffff;
    --text: #0f172a;
    --muted: #475569;
    --primary: #2563eb;
    --primary-hover: #1d4ed8;
    --ring: rgba(37, 99, 235, 0.35);
    --border: #e2e8f0;
    --shadow: 0 10px 25px rgba(2, 6, 23, 0.08);
    --radius: 16px;
}

* {
    box-sizing: border-box;
}

html,
body {
    height: 100%;
}

body {
    margin: 0;
    font-family: Inter, system-ui, -apple-system, Segoe UI, Roboto, 'Helvetica Neue', Arial, 'Noto Sans', 'Liberation Sans', sans-serif;
    color: var(--text);
    background: var(--bg);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

main {
    width: 100%;
    display: grid;
    place-items: center;
    padding: 24px 16px 48px;
    flex: 1;
}

.card {
    width: 100%;
    max-width: 420px;
    background: var(--card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 24px;
}

.title {
    font-size: 1.375rem;
    font-weight: 700;
    margin: 6px 0 4px;
    text-align: center;
    letter-spacing: 0.2px;
}

.subtitle {
    font-size: 0.9375rem;
    color: var(--muted);
    text-align: center;
    margin: 0 0 20px;
}

form {
    display: grid;
    gap: 14px;
}

.field {
    display: grid;
    gap: 8px;
}

label {
    font-size: 0.9375rem;
    font-weight: 600;
}

input[type="text"],
input[type="password"] {
    width: 100%;
    padding: 12px 14px;
    font-size: 1rem;
    border: 1px solid var(--border);
    border-radius: 12px;
    outline: none;
    background: #fff;
    transition: box-shadow .15s ease, border-color .15s ease;
}

input::placeholder {
    color: #94a3b8;
}

input:focus {
    border-color: var(--primary);
    box-shadow: 0 0 0 4px var(--ring);
}

.btn {
    appearance: none;
    border: none;
    border-radius: 999px;
    background: var(--primary);
    color: #fff;
    font-weight: 700;
    font-size: 1rem;
    padding: 12px 16px;
    cursor: pointer;
    transition: background .15s ease, transform .02s ease;
}

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

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

.btn:disabled {
    opacity: 0.6;
    cursor: not-allowed;
}

.error {
    background: #fef2f2;
    color: #991b1b;
    border: 1px solid #fecaca;
    border-radius: 10px;
    padding: 10px 12px;
    font-size: 0.9375rem;
    display: none;
}

.helper {
    font-size: 0.875rem;
    color: var(--muted);
    text-align: center;
    margin-top: 4px;
}

@media (max-width: 420px) {
    .card {
        padding: 18px;
    }

    .title {
        font-size: 1.25rem;
    }
}