/* ============================================
   CSS Variables (Custom Properties)
   ============================================ */
:root {
    /* Color Palette */
    --color-primary: #4CAF50;
    --color-primary-dark: #45a049;
    --color-primary-light: #e8f5e9;
    --color-secondary: #2196F3;
    --color-secondary-dark: #0b7dda;
    --color-danger: #f44336;
    --color-danger-dark: #da190b;
    --color-warning: #ff9800;
    --color-warning-light: #fff3e0;
    --color-warning-dark: #e65100;
    --color-info: #0066cc;
    --color-info-light: #f0f8ff;

    /* Neutral Colors */
    --color-text-primary: #333;
    --color-text-secondary: #666;
    --color-text-tertiary: #999;
    --color-bg-primary: #ffffff;
    --color-bg-secondary: #f5f5f5;
    --color-bg-tertiary: #fafafa;
    --color-border: #e0e0e0;
    --color-border-light: #ddd;
    --color-border-lighter: #ccc;

    /* Spacing */
    --spacing-xs: 5px;
    --spacing-sm: 10px;
    --spacing-md: 15px;
    --spacing-lg: 20px;
    --spacing-xl: 30px;
    --spacing-2xl: 50px;

    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 6px;
    --radius-lg: 8px;

    /* Shadows */
    --shadow-sm: 0 2px 4px rgba(0, 0, 0, 0.1);
    --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.1);
    --shadow-lg: 0 2px 10px rgba(0, 0, 0, 0.1);
    --shadow-hover: 0 4px 8px rgba(0, 0, 0, 0.2);

    /* Typography */
    --font-size-base: 16px;
    --font-size-sm: 12px;
    --font-size-md: 14px;
    --font-size-lg: 18px;
    --line-height-base: 1.6;

    /* Transitions */
    --transition-fast: 0.15s ease;
    --transition-base: 0.3s ease;
    --transition-slow: 0.5s ease;

    /* Container */
    --container-max-width: 900px;
    --container-padding: clamp(1rem, 5vw, 2rem);
}

/* ============================================
   CSS Reset & Base Styles
   ============================================ */
*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol", "Noto Color Emoji";
    font-size: var(--font-size-base);
    line-height: var(--line-height-base);
    color: var(--color-text-primary);
    background-color: var(--color-bg-secondary);
    margin: 0;
    padding: var(--container-padding);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ============================================
   Accessibility - Screen Reader Only
   ============================================ */
.sr-only {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* ============================================
   Skip to Content Link
   ============================================ */
.skip-link {
    position: absolute;
    top: -40px;
    left: 0;
    background: var(--color-primary);
    color: white;
    padding: var(--spacing-sm);
    text-decoration: none;
    z-index: 100;
}

.skip-link:focus {
    top: 0;
}

/* ============================================
   Main Container
   ============================================ */
.container {
    background-color: var(--color-bg-primary);
    border: 2px dashed var(--color-border-lighter);
    border-radius: var(--radius-lg);
    padding: clamp(1.25rem, 4vw, 1.875rem);
    box-shadow: var(--shadow-lg);
    max-width: var(--container-max-width);
    width: 100%;
    margin: 0 auto;
    flex: 1;
}

/* ============================================
   Page Header
   ============================================ */
.page-header {
    text-align: center;
    margin-bottom: var(--spacing-lg);
}

h1 {
    color: var(--color-text-primary);
    font-size: clamp(1.25rem, 4vw, 1.75rem);
    margin: 0 0 var(--spacing-sm) 0;
    font-weight: 700;
}

.subtitle {
    color: var(--color-text-secondary);
    margin: 0;
    font-size: clamp(0.875rem, 2vw, 1rem);
}

/* ============================================
   Info Sections
   ============================================ */
.description,
.warning,
.conversion-info {
    padding: var(--spacing-md);
    border-radius: var(--radius-sm);
    margin-bottom: var(--spacing-lg);
    font-size: var(--font-size-md);
    text-align: left;
    border-left: 4px solid;
}

.description {
    background-color: var(--color-info-light);
    border-left-color: var(--color-info);
}

.description strong {
    color: var(--color-info);
    display: block;
    margin-bottom: var(--spacing-sm);
}

.warning {
    background-color: var(--color-warning-light);
    border-left-color: var(--color-warning);
}

.warning strong {
    color: var(--color-warning-dark);
    display: block;
    margin-bottom: var(--spacing-sm);
}

.conversion-info {
    background-color: var(--color-primary-light);
    border-left-color: var(--color-primary);
}

.conversion-title {
    margin-top: 0;
    color: #2e7d32;
    font-size: var(--font-size-lg);
}

.description ul,
.warning ul,
.conversion-info ul {
    margin: 0;
    padding-left: var(--spacing-lg);
}

.description li,
.warning li,
.conversion-info li {
    margin-bottom: var(--spacing-xs);
    line-height: var(--line-height-base);
}

.description li:last-child,
.warning li:last-child,
.conversion-info li:last-child {
    margin-bottom: 0;
}

.conversion-info ul {
    list-style-type: none;
    padding-left: 0;
}

.conversion-info li {
    padding: var(--spacing-xs) 0;
}

.conversion-info .note {
    font-size: 13px;
    color: var(--color-text-secondary);
    margin-top: var(--spacing-sm);
    margin-bottom: 0;
}

/* ============================================
   Step Sections
   ============================================ */
.step-section {
    background-color: var(--color-bg-tertiary);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-md);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-md);
}

.step-title {
    margin: 0 0 var(--spacing-md) 0;
    padding-bottom: var(--spacing-sm);
    border-bottom: 2px solid var(--color-border-light);
    color: var(--color-text-primary);
    font-size: var(--font-size-lg);
    font-weight: 600;
}

/* ============================================
   Detection Result
   ============================================ */
.detection-result {
    padding: 12px;
    border-radius: var(--radius-sm);
    margin: var(--spacing-md) 0 0 0;
    font-weight: bold;
    display: none;
    animation: slideIn var(--transition-base);
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: translateY(-10px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.detection-result.show {
    display: block;
}

.detection-result.detected {
    background-color: var(--color-primary-light);
    color: #2e7d32;
    border-left: 4px solid var(--color-primary);
}

.detection-result.not-detected {
    background-color: var(--color-warning-light);
    color: var(--color-warning-dark);
    border-left: 4px solid var(--color-warning);
}

/* ============================================
   Form Elements
   ============================================ */
/* Hidden file input */
.file-input-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border-width: 0;
}

/* ============================================
   Drag & Drop Zone
   ============================================ */
.dropzone {
    width: 100%;
    min-height: 200px;
    border: 2px dashed var(--color-border);
    border-radius: var(--radius-md);
    background-color: var(--color-bg-tertiary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}

.dropzone::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    bottom: 0;
    background: linear-gradient(135deg, transparent 0%, rgba(76, 175, 80, 0.03) 100%);
    opacity: 0;
    transition: opacity var(--transition-base);
}

.dropzone:hover::before {
    opacity: 1;
}

.dropzone:hover {
    border-color: var(--color-primary);
    background-color: rgba(76, 175, 80, 0.02);
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

.dropzone:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(76, 175, 80, 0.1);
}

.dropzone.drag-over {
    border-color: var(--color-primary);
    background-color: var(--color-primary-light);
    border-style: solid;
    border-width: 3px;
    animation: pulse 0.6s ease-in-out;
}

@keyframes pulse {
    0%, 100% {
        transform: scale(1);
    }
    50% {
        transform: scale(1.02);
    }
}

.dropzone-content {
    text-align: center;
    padding: var(--spacing-lg);
    pointer-events: none;
}

.dropzone-icon {
    width: 64px;
    height: 64px;
    margin: 0 auto var(--spacing-md);
    color: var(--color-primary);
    opacity: 0.6;
    transition: all var(--transition-base);
}

.dropzone:hover .dropzone-icon {
    opacity: 1;
    transform: translateY(-4px);
}

.dropzone.drag-over .dropzone-icon {
    opacity: 1;
    transform: scale(1.1);
    animation: bounce 0.6s ease-in-out;
}

@keyframes bounce {
    0%, 100% {
        transform: translateY(0);
    }
    50% {
        transform: translateY(-10px);
    }
}

.dropzone-text {
    font-size: var(--font-size-lg);
    font-weight: 600;
    color: var(--color-text-primary);
    margin: 0 0 var(--spacing-xs) 0;
}

.dropzone-subtext {
    font-size: var(--font-size-md);
    color: var(--color-text-secondary);
    margin: 0 0 var(--spacing-md) 0;
}

.dropzone-button {
    display: inline-block;
    padding: var(--spacing-sm) var(--spacing-lg);
    background-color: var(--color-primary);
    color: white;
    border-radius: var(--radius-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-base);
    pointer-events: auto;
}

.dropzone-button:hover {
    background-color: var(--color-primary-dark);
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

.dropzone-button:focus {
    outline: 2px solid var(--color-primary);
    outline-offset: 2px;
}

/* ============================================
   Buttons
   ============================================ */
.button-group {
    display: flex;
    gap: var(--spacing-sm);
    justify-content: center;
    flex-wrap: wrap;
}

button {
    color: white;
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: var(--font-size-base);
    font-weight: 600;
    transition: all var(--transition-base);
    min-width: 150px;
    position: relative;
    overflow: hidden;
}

button::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    width: 0;
    height: 0;
    border-radius: 50%;
    background: rgba(255, 255, 255, 0.3);
    transform: translate(-50%, -50%);
    transition: width var(--transition-base), height var(--transition-base);
}

button:active::before {
    width: 300px;
    height: 300px;
}

button:hover:not(:disabled) {
    transform: translateY(-2px);
    box-shadow: var(--shadow-hover);
}

button:focus {
    outline: none;
    box-shadow: 0 0 0 3px rgba(0, 0, 0, 0.1);
}

button:focus:not(:focus-visible) {
    box-shadow: none;
}

button:focus-visible {
    box-shadow: 0 0 0 3px rgba(0, 0, 0, 0.2);
}

button:disabled {
    background-color: var(--color-border-lighter);
    cursor: not-allowed;
    transform: none;
    opacity: 0.6;
}

#convertBtn {
    background-color: var(--color-primary);
    width: 100%;
    max-width: 300px;
    display: block;
    margin: 0 auto;
}

#convertBtn:hover:not(:disabled) {
    background-color: var(--color-primary-dark);
}

#downloadBtn {
    background-color: var(--color-secondary);
}

#downloadBtn:hover:not(:disabled) {
    background-color: var(--color-secondary-dark);
}

#clearBtn {
    background-color: var(--color-danger);
}

#clearBtn:hover:not(:disabled) {
    background-color: var(--color-danger-dark);
}

/* ============================================
   Preview Section
   ============================================ */
.preview-section {
    margin-top: var(--spacing-lg);
    text-align: center;
}

#preview {
    max-width: 100%;
    height: auto;
    border-radius: var(--radius-sm);
    box-shadow: var(--shadow-md);
    display: none;
    animation: fadeIn var(--transition-slow);
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

#preview.show {
    display: block;
    margin: 0 auto;
}

#canvas {
    display: none;
}

.info {
    margin-top: var(--spacing-sm);
    padding: var(--spacing-sm);
    color: var(--color-text-secondary);
    font-size: var(--font-size-md);
    background-color: var(--color-bg-primary);
    border-radius: var(--radius-sm);
    border: 1px solid var(--color-border);
}

/* ============================================
   Footer
   ============================================ */
.footer {
    background-color: var(--color-bg-secondary);
    border-top: 1px solid var(--color-border-light);
    margin-top: var(--spacing-2xl);
    padding: var(--spacing-xl) var(--container-padding);
    text-align: center;
}

.footer-content {
    max-width: var(--container-max-width);
    margin: 0 auto;
}

.footer-note {
    font-size: var(--font-size-md);
    color: var(--color-text-secondary);
    margin-bottom: var(--spacing-md);
}

.footer-note a {
    color: var(--color-info);
    text-decoration: none;
    transition: color var(--transition-base), text-decoration var(--transition-base);
}

.footer-note a:hover {
    text-decoration: underline;
    color: var(--color-primary);
}

.footer-note a:focus {
    outline: 2px solid var(--color-info);
    outline-offset: 2px;
}

.footer-analytics {
    font-size: var(--font-size-sm);
    color: var(--color-text-tertiary);
    line-height: var(--line-height-base);
    margin-bottom: var(--spacing-md);
    padding: var(--spacing-sm);
    background-color: var(--color-bg-primary);
    border-radius: var(--radius-sm);
}

.footer-copyright {
    font-size: var(--font-size-sm);
    color: var(--color-text-tertiary);
    margin-top: var(--spacing-md);
}

.footer-copyright a {
    color: var(--color-text-tertiary);
    text-decoration: none;
    transition: color var(--transition-base);
}

.footer-copyright a:hover {
    color: var(--color-text-secondary);
    text-decoration: underline;
}

/* ============================================
   Media Queries - Responsive Design
   ============================================ */

/* Small devices (landscape phones, 576px and up) */
@media (max-width: 576px) {
    :root {
        --font-size-base: 14px;
    }

    .button-group {
        flex-direction: column;
    }

    button {
        width: 100%;
        min-width: unset;
    }

    .step-section {
        padding: var(--spacing-md);
    }

    h1 {
        font-size: 1.25rem;
    }

    .dropzone {
        min-height: 180px;
    }

    .dropzone-icon {
        width: 48px;
        height: 48px;
    }

    .dropzone-text {
        font-size: var(--font-size-base);
    }

    .dropzone-content {
        padding: var(--spacing-md);
    }
}

/* Medium devices (tablets, 768px and up) */
@media (min-width: 577px) and (max-width: 768px) {
    .container {
        padding: var(--spacing-xl);
    }
}

/* Large devices (desktops, 992px and up) */
@media (min-width: 992px) {
    .container {
        padding: var(--spacing-2xl);
    }

    .button-group {
        gap: var(--spacing-md);
    }
}

/* Extra large devices (large desktops, 1200px and up) */
@media (min-width: 1200px) {
    body {
        padding: var(--spacing-2xl) var(--container-padding);
    }
}

/* ============================================
   Reduced Motion - Accessibility
   ============================================ */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* ============================================
   Print Styles
   ============================================ */
@media print {
    body {
        background-color: white;
    }

    .container {
        border: 1px solid black;
        box-shadow: none;
    }

    button,
    input[type="file"],
    .footer {
        display: none;
    }

    .preview-section {
        page-break-inside: avoid;
    }
}

/* ============================================
   Dark Mode Support (準備)
   ============================================ */
@media (prefers-color-scheme: dark) {
    /* ダークモード対応は将来的に実装可能 */
    /*
    :root {
        --color-text-primary: #e0e0e0;
        --color-bg-primary: #1e1e1e;
        --color-bg-secondary: #121212;
    }
    */
}