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

html,
body {
    height: 100%;
}

body {
    margin: 0;
    font-family: system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background: #0e0e18;
    color: #e8eaf0;
    line-height: 1.5;
}

:focus-visible {
    outline: 2px solid #4da3ff;
    outline-offset: 2px;
}

.app {
    min-height: 100%;
    display: flex;
    flex-direction: column;
    padding: 1.5rem 1rem 2rem;
}

.app__header {
    text-align: center;
    margin-bottom: 2rem;
}

.app__title {
    margin: 0 0 0.35rem;
    font-size: clamp(1.5rem, 4vw, 2rem);
    font-weight: 600;
    letter-spacing: -0.02em;
}

.app__subtitle {
    margin: 0;
    color: #9aa0b4;
    font-size: 0.95rem;
}

.app__main {
    flex: 1;
    display: flex;
    align-items: center;
    justify-content: center;
}

.app__footer {
    text-align: center;
    margin-top: 2rem;
    font-size: 0.85rem;
}

.app__footer a {
    color: #6b9fd4;
    text-decoration: none;
}

.app__footer a:hover {
    text-decoration: underline;
}

.panel {
    width: 100%;
    max-width: 52rem;
    background: #1a1a28;
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 12px;
    padding: 1.5rem;
    display: grid;
    gap: 2rem;
}

@media (min-width: 640px) {
    .panel {
        grid-template-columns: 1fr 1fr;
        padding: 2rem;
    }
}

.tabs {
    display: flex;
    gap: 0.25rem;
    margin-bottom: 1.25rem;
    background: #12121c;
    border-radius: 8px;
    padding: 0.25rem;
}

.tabs__btn {
    flex: 1;
    padding: 0.55rem 0.75rem;
    border: none;
    border-radius: 6px;
    background: transparent;
    color: #9aa0b4;
    font: inherit;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.15s, color 0.15s;
}

.tabs__btn:hover {
    color: #e8eaf0;
}

.tabs__btn--active {
    background: #2a3a52;
    color: #e8eaf0;
}

.field {
    display: block;
    margin-bottom: 1rem;
}

.field__label {
    display: block;
    margin-bottom: 0.35rem;
    font-size: 0.85rem;
    font-weight: 500;
    color: #b8bcc8;
}

.field__input {
    width: 100%;
    padding: 0.65rem 0.85rem;
    border: 1px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    background: #12121c;
    color: #e8eaf0;
    font: inherit;
    font-size: 0.95rem;
    transition: border-color 0.15s;
}

.field__input::placeholder {
    color: #6b7280;
}

.field__input:hover {
    border-color: rgba(255, 255, 255, 0.18);
}

.field__input:focus {
    outline: none;
    border-color: #4da3ff;
}

.field__textarea {
    resize: vertical;
    min-height: 7rem;
}

.field__hint {
    margin: -0.5rem 0 0;
    font-size: 0.8rem;
    color: #6b7280;
}

.panel__preview {
    display: flex;
    align-items: center;
    justify-content: center;
}

.preview {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
    width: 100%;
}

.preview__frame {
    width: 100%;
    max-width: 280px;
    aspect-ratio: 1;
    display: grid;
    place-items: center;
    background: #12121c;
    border: 1px solid rgba(255, 255, 255, 0.08);
    border-radius: 12px;
    padding: 1rem;
}

.preview__frame > * {
    grid-area: 1 / 1;
}

.preview__placeholder {
    margin: 0;
    text-align: center;
    font-size: 0.9rem;
    color: #6b7280;
    padding: 0 1rem;
    max-width: 100%;
    align-self: center;
    justify-self: center;
}

#qr-canvas {
    display: block;
    max-width: 100%;
    max-height: 100%;
    width: auto;
    height: auto;
    border-radius: 4px;
}

.btn {
    padding: 0.65rem 1.5rem;
    border: none;
    border-radius: 8px;
    font: inherit;
    font-size: 0.95rem;
    font-weight: 500;
    cursor: pointer;
    transition: background 0.15s, opacity 0.15s;
}

.btn--primary {
    background: #3b82c4;
    color: #fff;
}

.btn--primary:hover:not(:disabled) {
    background: #4da3ff;
}

.btn--primary:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}