:root {
    --primary-color: #6366f1;
    --primary-hover: #4f46e5;
    --secondary-color: #10b981;
    --bg-color: #ffffff;
    --card-bg: #ffffff;
    --card-border: #e5e7eb;
    --text-primary: #181818;
    --text-secondary: #6b7280;
    --input-bg: #f9fafb;
    --success-color: #22c55e;
    --error-color: #ef4444;
    --warning-color: #f59e0b;
}

.dark-mode {
    --bg-color: #0f172a;
    --card-bg: #1e293b;
    --card-border: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #94a3b8;
    --input-bg: #0f172a;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: var(--bg-color);
    color: var(--text-primary);
    min-height: 100vh;
    line-height: 1.6;
    transition: background 0.3s, color 0.3s;
}

/* Container */
.container {
    max-width: 900px;
    margin: 0 auto;
    padding: 20px;
    border: 1.5px solid var(--card-border);
    border-radius: 10px;
    background: var(--card-bg);
    transition: background 0.3s, border-color 0.3s;
}

/* Header */
header {
    text-align: center;
    margin-bottom: 20px;
    padding: 20px;
}

header h1 {
    font-size: 2.5rem;
    margin-bottom: 10px;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

header p {
    color: var(--text-primary);
    font-size: 1.1rem;
}

/* Client-side note */
.client-side-note {
    font-size: 0.9rem;
    color: var(--text-primary);
    margin-top: 10px;
    padding: 8px 16px;
    background: rgba(99, 102, 241, 0.1);
    border-radius: 8px;
    display: inline-block;
}

.dark-mode .client-side-note {
    background: rgba(99, 102, 241, 0.15);
    color: #a5b4fc;
}

/* Topbar */
.topbar {
    display: flex;
    justify-content: flex-end;
    align-items: center;
    gap: 1.2rem;
    margin-top: 1.2rem;
    padding: 0 20px;
}

.github-link svg,
#theme-icon svg {
    width: 28px !important;
    height: 28px !important;
    display: block;
    color: var(--text-primary);
    fill: var(--text-primary);
    transition: color 0.2s, fill 0.2s;
}

.theme-toggle-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 0.2em;
    border-radius: 50%;
    background: none;
    border: none;
    cursor: pointer;
    transition: background 0.2s;
}

.theme-toggle-btn:focus {
    outline: none;
}

.theme-toggle {
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.github-link {
    display: flex;
    align-items: center;
    text-decoration: none;
    color: inherit;
    transition: color 0.2s;
}

.github-link:hover svg {
    color: var(--primary-color);
}

.sun-icon, .moon-icon {
    width: 28px;
    height: 28px;
    display: block;
    fill: var(--text-primary);
    stroke: none;
    transition: fill 0.2s;
}

/* Tabs */
.tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 20px;
}

.tab-btn {
    flex: 1;
    padding: 15px 30px;
    font-size: 1rem;
    font-weight: 600;
    border: 2px solid var(--card-border);
    background: var(--card-bg);
    color: var(--text-secondary);
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.tab-btn:hover {
    border-color: var(--primary-color);
    color: var(--text-primary);
}

.tab-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

/* Tab Content */
.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

.tab-content.active {
    display: block;
}

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

/* Sections */
.input-section,
.output-section {
    background: var(--card-bg);
    border: 1px solid var(--card-border);
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 20px;
    transition: background 0.3s, border-color 0.3s;
}

.input-section h2,
.output-section h2 {
    font-size: 1.08rem;
    margin-bottom: 15px;
    color: var(--text-primary);
    font-weight: 700;
    letter-spacing: 0.01em;
    transition: color 0.3s;
}

/* Input Type Selector */
.input-type-selector,
.output-type-selector .output-options {
    display: flex;
    gap: 15px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}

.input-type-selector label,
.output-type-selector label {
    display: flex;
    align-items: center;
    gap: 8px;
    cursor: pointer;
    padding: 10px 20px;
    background: var(--input-bg);
    border: 2px solid var(--card-border);
    border-radius: 8px;
    color: var(--text-primary);
    font-weight: 500;
    font-size: 0.96rem;
    transition: all 0.3s;
}

.input-type-selector input,
.output-type-selector input {
    accent-color: var(--primary-color);
    background-color: var(--card-bg);
    border-radius: 50%;
    width: 1.1em;
    height: 1.1em;
    border: 2px solid var(--primary-color);
    margin-right: 0.5em;
    transition: background 0.2s, border-color 0.2s;
}

.input-type-selector label:hover,
.output-type-selector label:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.input-type-selector input:checked + span,
.output-type-selector input:checked + span {
    color: var(--primary-color);
    font-weight: 700;
}

.input-type-selector input:focus,
.output-type-selector input:focus {
    outline: 2px solid var(--primary-color);
    outline-offset: 2px;
}

/* Text Areas */
textarea {
    width: 100%;
    min-height: 150px;
    padding: 15px;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.95rem;
    background: var(--input-bg);
    border: 2px solid var(--card-border);
    border-radius: 8px;
    color: var(--text-primary);
    resize: vertical;
    transition: border-color 0.3s ease, background 0.3s, color 0.3s;
}

textarea:focus {
    outline: none;
    border-color: var(--primary-color);
}

textarea::placeholder {
    color: var(--text-secondary);
}

/* File Drop Zone */
.file-drop-zone {
    position: relative;
    border: 2px dashed var(--card-border);
    border-radius: 12px;
    padding: 40px 20px;
    text-align: center;
    cursor: pointer;
    transition: all 0.3s ease;
    background: var(--input-bg);
}

.file-drop-zone:hover,
.file-drop-zone.dragover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.file-drop-zone.dragover {
    border-color: var(--secondary-color);
    background: rgba(16, 185, 129, 0.12); /* subtle green tint for drop */
    box-shadow: 0 0 0 3px rgba(16, 185, 129, 0.15);
    transition: border-color 0.2s, background 0.2s, box-shadow 0.2s;
}

.file-drop-zone input[type="file"] {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    opacity: 0;
    cursor: pointer;
}

.drop-content .icon {
    font-size: 3rem;
    display: block;
    margin-bottom: 10px;
    color: var(--primary-color);
}

.drop-content p {
    color: var(--text-primary);
    font-size: 1rem;
    margin-bottom: 5px;
    font-weight: 500;
}

.drop-content small {
    color: var(--primary-color);
    font-size: 0.92rem;
    font-weight: 400;
}

/* File Preview */
.file-preview {
    margin-top: 15px;
    padding: 15px;
    background: var(--input-bg);
    border-radius: 8px;
    border: 1px solid var(--card-border);
    transition: background 0.3s, border-color 0.3s;
}

.file-preview .preview-image {
    max-width: 100%;
    max-height: 200px;
    border-radius: 8px;
    margin-bottom: 10px;
}

.file-preview .file-details {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
}

.file-preview .file-name {
    font-weight: 600;
    color: var(--text-primary);
}

.file-preview .file-size {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.file-preview .remove-file {
    padding: 5px 15px;
    background: var(--error-color);
    border: none;
    border-radius: 5px;
    color: white;
    cursor: pointer;
    font-size: 0.9rem;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 20px;
    font-size: 0.95rem;
    font-weight: 600;
    border: 2px solid var(--card-border);
    background: var(--card-bg);
    color: var(--text-primary);
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.btn:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    border-color: var(--primary-color);
    color: white;
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-hover), #4338ca);
    border-color: var(--primary-hover);
}

.btn-secondary {
    background: var(--card-bg);
    border-color: var(--card-border);
    color: var(--text-primary);
}

.btn-secondary:hover {
    border-color: var(--secondary-color);
    background: var(--card-bg);
    color: var(--text-primary);
}

.btn-add {
    background: transparent;
    border: 2px dashed var(--primary-color);
    color: var(--primary-color);
}

.btn-add:hover {
    background: rgba(99, 102, 241, 0.1);
}

.btn-remove {
    padding: 8px;
    border: none;
    background: transparent;
    color: var(--error-color);
    border-radius: 6px;
    transition: background 0.3s;
}

.btn-remove:hover {
    background: rgba(239, 68, 68, 0.1);
}

.btn-lg {
    padding: 15px 30px;
    font-size: 1.1rem;
}

/* Action Button */
.action-btn {
    width: 100%;
    padding: 15px 30px;
    font-size: 1.1rem;
    font-weight: 600;
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    border: none;
    border-radius: 10px;
    color: white;
    cursor: pointer;
    margin-top: 15px;
    transition: all 0.3s ease;
}

.action-btn:hover {
    background: linear-gradient(135deg, var(--primary-hover), #4338ca);
}

/* Button Groups */
.btn-group {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
}

.btn-group-block {
    margin: 20px 0;
}

.btn-group-block .btn {
    flex: 1;
}

/* Output Actions */
.output-actions {
    display: flex;
    gap: 10px;
    margin-top: 15px;
    flex-wrap: wrap;
}

.output-actions .btn {
    flex: 1;
    min-width: 0;
}

.action-buttons {
    margin-top: 10px;
}

/* Copy & Download Buttons */
.copy-btn,
.download-btn {
    background: var(--card-bg);
    color: var(--text-primary);
    border: 2px solid var(--card-border);
    transition: all 0.3s ease;
}

.copy-btn:hover {
    border-color: var(--primary-color);
    background: rgba(99, 102, 241, 0.1);
}

.download-btn:hover {
    border-color: var(--secondary-color);
    background: rgba(16, 185, 129, 0.1);
}

/* Decode Output Sections */
.decode-output {
    display: none;
}

.decode-output.active {
    display: block;
}

/* Image Preview */
.image-preview {
    background: var(--input-bg);
    border: 2px solid var(--card-border);
    border-radius: 8px;
    padding: 20px;
    text-align: center;
    min-height: 150px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background 0.3s, border-color 0.3s;
}

.image-preview img {
    max-width: 100%;
    max-height: 400px;
    border-radius: 8px;
}

/* File Info */
.file-info {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 20px;
    background: var(--input-bg);
    border: 2px solid var(--card-border);
    border-radius: 8px;
    transition: background 0.3s, border-color 0.3s;
}

.file-info .icon {
    font-size: 3rem;
}

.file-info .details .filename {
    font-weight: 600;
    font-size: 1.1rem;
    color: var(--text-primary);
    margin-bottom: 5px;
}

.file-info .details .filesize,
.file-info .details .filetype {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Status Messages */
.status {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    padding: 15px 30px;
    border-radius: 10px;
    font-weight: 500;
    z-index: 1000;
    animation: slideUp 0.3s ease;
}

@keyframes slideUp {
    from { opacity: 0; transform: translateX(-50%) translateY(20px); }
    to { opacity: 1; transform: translateX(-50%) translateY(0); }
}

.status.success {
    background: var(--success-color);
    color: white;
}

.status.error {
    background: var(--error-color);
    color: white;
}

.status.warning {
    background: var(--warning-color);
    color: white;
}

/* Hidden Class */
.hidden {
    display: none !important;
}

/* Footer */
footer {
    color: var(--text-primary);
    background: transparent;
    text-align: center;
    padding: 30px 0 10px 0;
    font-size: 0.95rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.3em;
}

footer a {
    color: var(--primary-color);
    text-decoration: underline;
    font-weight: 600;
    transition: color 0.2s;
}

footer .copyright {
    color: var(--text-primary);
    font-size: 0.9em;
    font-weight: 500;
    margin-top: 0.5em;
}

/* Visually Hidden */
.visually-hidden {
    position: absolute !important;
    height: 1px;
    width: 1px;
    overflow: hidden;
    clip: rect(1px, 1px, 1px, 1px);
    white-space: nowrap;
}

/* Dark Mode Overrides */
.dark-mode body,
.dark-mode {
    background: #0a0a0a;
}

.dark-mode .container,
.dark-mode .input-section,
.dark-mode .output-section,
.dark-mode .file-drop-zone,
.dark-mode .file-preview,
.dark-mode .image-preview,
.dark-mode .file-info {
    background: #181818 !important;
    border-color: #333 !important;
}

.dark-mode .tab-btn {
    background: rgb(24, 24, 24) !important;
}

.dark-mode textarea,
.dark-mode input[type="text"],
.dark-mode input[type="file"] {
    background: #222 !important;
    border-color: #333 !important;
    color: #fff !important;
}

.dark-mode textarea:focus,
.dark-mode input[type="text"]:focus {
    border-color: var(--primary-color) !important;
}

.dark-mode .btn {
    background: #222;
    border-color: #333;
    color: #fff;
}

.dark-mode .btn:hover {
    background: #333;
    border-color: var(--primary-color);
}

.dark-mode .btn-add {
    background: transparent;
    color: var(--primary-color);
}

.dark-mode .btn-primary {
    background: linear-gradient(135deg, var(--primary-color), var(--primary-hover));
    border-color: var(--primary-color);
    color: white;
}

.dark-mode .btn-primary:hover {
    background: linear-gradient(135deg, var(--primary-hover), #4338ca);
    border-color: var(--primary-hover);
}

.dark-mode .btn-secondary {
    background: #222;
    border-color: #333;
    color: #fff;
}

.dark-mode .btn-secondary:hover {
    border-color: var(--secondary-color);
    background: #222;
    color: #fff;
}

.dark-mode .copy-btn,
.dark-mode .download-btn {
    background: #222;
    color: #fff;
    border-color: #333;
}

.dark-mode .copy-btn:hover {
    border-color: var(--primary-color);
    background: #333;
}

.dark-mode .download-btn:hover {
    border-color: var(--secondary-color);
    background: #333;
}

.dark-mode .input-type-selector label,
.dark-mode .output-type-selector label {
    background: #222;
    border-color: #333;
    color: #e5e7eb;
}

.dark-mode .input-type-selector label:hover,
.dark-mode .output-type-selector label:hover {
    background: #333;
    border-color: var(--primary-color);
}

.dark-mode .input-type-selector input:checked + span,
.dark-mode .output-type-selector input:checked + span {
    color: #a5b4fc;
}

.dark-mode footer a {
    color: #a5b4fc;
}

.dark-mode .file-info .filename,
.dark-mode .file-preview .file-name {
    color: #a5b4fc;
}

/* Scrollbar Styling */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: var(--input-bg);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb {
    background: var(--card-border);
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: var(--text-secondary);
}

/* Selection */
::selection {
    background: var(--primary-color);
    color: white;
}

/* Responsive */
@media (max-width: 768px) {
    header h1 {
        font-size: 2rem;
    }

    .tabs {
        flex-direction: column;
    }

    .input-type-selector,
    .output-type-selector .output-options {
        flex-direction: column;
    }

    .btn-group-block {
        flex-direction: column;
    }

    .btn-group-block .btn {
        width: 100%;
    }

    .output-actions {
        flex-direction: column;
    }

    .output-actions .btn {
        width: 100%;
    }
}

@media (min-width: 769px) {
    .output-actions .btn {
        flex: 1;
    }
}