:root {
    --primary: #1a73e8;
    --primary-hover: #1557b0;
    --primary-light: #e8f0fe;
    --primary-light-hover: #d2e3fc;
    --on-primary: #ffffff;
    --surface: #ffffff;
    --surface-dim: #f8fafc;
    --background: #f1f5f9;
    --on-surface: #1e293b;
    --on-surface-variant: #64748b;
    --outline: #e2e8f0;
    --qr-dark: #1e293b;
    --qr-light: #ffffff;
    --shadow: 0 10px 15px -3px rgba(0,0,0,0.08), 0 4px 6px -4px rgba(0,0,0,0.04);
    --shadow-lg: 0 20px 25px -5px rgba(0,0,0,0.08), 0 8px 10px -6px rgba(0,0,0,0.04);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 24px;
}

[data-theme="dark"] {
    --primary: #8ab4f8;
    --primary-hover: #aecbfa;
    --primary-light: #1e3a5f;
    --primary-light-hover: #264a73;
    --on-primary: #1e293b;
    --surface: #1e293b;
    --surface-dim: #162032;
    --background: #0f172a;
    --on-surface: #e2e8f0;
    --on-surface-variant: #94a3b8;
    --outline: #334155;
    --shadow: 0 10px 15px -3px rgba(0,0,0,0.35), 0 4px 6px -4px rgba(0,0,0,0.2);
    --shadow-lg: 0 20px 25px -5px rgba(0,0,0,0.4), 0 8px 10px -6px rgba(0,0,0,0.25);
}

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

*,
*::before,
*::after {
    transition: background-color 0.3s ease, border-color 0.3s ease, color 0.3s ease, box-shadow 0.3s ease;
}

body {
    font-family: 'Roboto', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--background);
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 1.5rem;
}

.material-symbols-rounded {
    font-variation-settings: 'FILL' 1, 'wght' 400, 'GRAD' 0, 'opsz' 24;
}

.card {
    background: var(--surface);
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-lg);
    width: 100%;
    max-width: 400px;
    overflow: hidden;
}

.card-header {
    padding: 1.75rem 1.75rem 0;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.card-header h1 {
    font-family: 'Google Sans', sans-serif;
    font-size: 1.5rem;
    font-weight: 500;
    color: var(--on-surface);
}

.theme-toggle {
    background: var(--surface-dim);
    border: none;
    border-radius: var(--radius-sm);
    width: 40px;
    height: 40px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--on-surface-variant);
}

.theme-toggle:hover {
    background: var(--outline);
    color: var(--on-surface);
}

.theme-toggle .material-symbols-rounded {
    font-size: 1.25rem;
}

.icon-light, .icon-dark { display: none; }
:root .icon-light { display: block; }
[data-theme="dark"] .icon-light { display: none; }
[data-theme="dark"] .icon-dark { display: block; }

.card-body {
    padding: 1.5rem 1.75rem;
}

.input-group {
    position: relative;
}

.input-field {
    width: 100%;
    padding: 1rem 1rem 1rem 3rem;
    font-family: 'Roboto', sans-serif;
    font-size: 1rem;
    color: var(--on-surface);
    background: var(--surface-dim);
    border: 1px solid var(--outline);
    border-radius: var(--radius-md);
}

.input-field::placeholder {
    color: var(--on-surface-variant);
}

.input-field:hover {
    background: var(--outline);
}

.input-field:focus {
    outline: none;
    background: var(--surface);
    border-color: var(--primary);
    box-shadow: 0 0 0 3px var(--primary-light);
}

.input-icon {
    position: absolute;
    left: 0.875rem;
    top: 50%;
    transform: translateY(-50%);
    color: var(--on-surface-variant);
    font-size: 1.25rem;
    pointer-events: none;
}

.input-field:focus + .input-icon {
    color: var(--primary);
}

.btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    width: 100%;
    margin-top: 1rem;
    padding: 0.875rem 1.5rem;
    font-family: 'Google Sans', sans-serif;
    font-size: 0.9375rem;
    font-weight: 500;
    color: var(--on-primary);
    background: var(--primary);
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: transform 0.1s;
}

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

.btn:active {
    transform: translateY(0);
}

.btn .material-symbols-rounded {
    font-size: 1.25rem;
}

.divider {
    height: 1px;
    background: var(--outline);
    margin: 0 1.75rem;
}

.output-section {
    padding: 1.5rem 1.75rem 1.75rem;
    display: flex;
    flex-direction: column;
    align-items: center;
}

.qr-container {
    width: 224px;
    height: 224px;
    display: flex;
    align-items: center;
    justify-content: center;
    position: relative;
}

.placeholder {
    position: absolute;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
    color: var(--on-surface-variant);
    transition: opacity 0.2s;
}

.placeholder.hidden {
    opacity: 0;
    pointer-events: none;
}

.placeholder-icon {
    width: 80px;
    height: 80px;
    background: var(--surface-dim);
    border-radius: var(--radius-lg);
    display: flex;
    align-items: center;
    justify-content: center;
}

.placeholder-icon .material-symbols-rounded {
    font-size: 2.5rem;
    color: var(--outline);
}

.placeholder-text {
    font-size: 0.875rem;
    text-align: center;
}

#qrcode {
    display: none;
    background: transparent;
    border-radius: var(--radius-md);
    padding: 12px;
    animation: fadeIn 0.4s ease-out;
}

[data-theme="dark"] #qrcode {
    background: var(--qr-light);
    box-shadow: var(--shadow);
}

#qrcode canvas,
#qrcode img {
    width: 200px;
    height: 200px;
}

#qrcode.visible {
    display: flex;
}

@keyframes fadeIn {
    from { opacity: 0; transform: scale(0.95); }
    to { opacity: 1; transform: scale(1); }
}

.qr-actions {
    display: flex;
    gap: 0.75rem;
    margin-top: 1.25rem;
    height: 36px;
}

.qr-actions.hidden {
    visibility: hidden;
}

.btn-secondary {
    display: flex;
    align-items: center;
    gap: 0.375rem;
    padding: 0.625rem 1rem;
    font-family: 'Google Sans', sans-serif;
    font-size: 0.8125rem;
    font-weight: 500;
    color: var(--primary);
    background: var(--primary-light);
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
}

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

.btn-secondary .material-symbols-rounded {
    font-size: 1.125rem;
}

.card-footer {
    padding: 1.25rem 1.75rem;
    background: var(--surface-dim);
    border-top: 1px solid var(--outline);
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
}

.footer-text {
    font-size: 0.75rem;
    color: var(--on-surface-variant);
}

.footer-link {
    color: var(--primary);
    text-decoration: none;
}

.footer-link:hover {
    text-decoration: underline;
}

.toast {
    position: fixed;
    bottom: 1.5rem;
    left: 50%;
    transform: translateX(-50%) translateY(100px);
    background: var(--on-surface);
    color: var(--surface);
    padding: 0.875rem 1.25rem;
    border-radius: var(--radius-sm);
    font-size: 0.875rem;
    box-shadow: var(--shadow);
    opacity: 0;
    transition: opacity 0.3s, transform 0.3s;
    z-index: 100;
}

.toast.show {
    opacity: 1;
    transform: translateX(-50%) translateY(0);
}

@media (max-width: 480px) {
    body {
        padding: 1rem;
        align-items: flex-start;
        padding-top: 2rem;
    }
    .card {
        border-radius: var(--radius-lg);
    }
    .card-header, .card-body, .output-section {
        padding-left: 1.25rem;
        padding-right: 1.25rem;
    }
    .card-footer {
        padding-left: 1.25rem;
        padding-right: 1.25rem;
    }
    .divider {
        margin: 0 1.25rem;
    }
}