/* ── Reset & Variables ─────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
    --primary: #4361ee;
    --primary-dark: #3451d1;
    --success: #2ec4b6;
    --danger: #e63946;
    --warning: #f4a261;
    --bg: #f5f6fa;
    --surface: #ffffff;
    --text: #2d3436;
    --text-light: #636e72;
    --border: #dfe6e9;
    --sidebar-w: 260px;
    --radius: 8px;
    --shadow: 0 2px 8px rgba(0,0,0,0.08);
    --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}

html { font-size: 15px; }
body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    display: flex;
    min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }

/* ── Sidebar ──────────────────────────────────── */
.sidebar {
    width: var(--sidebar-w);
    background: var(--surface);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    position: fixed;
    top: 0; left: 0; bottom: 0;
    z-index: 100;
    overflow-y: auto;
    transition: transform .25s ease;
}

.sidebar-header {
    padding: 1.2rem 1.4rem;
    border-bottom: 1px solid var(--border);
}

.logo {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--primary);
    display: flex;
    align-items: center;
    gap: .5rem;
}

.sidebar-nav { padding: .5rem 0; flex: 1; }

.nav-category-btn {
    width: 100%;
    display: flex;
    align-items: center;
    gap: .5rem;
    padding: .65rem 1.4rem;
    border: none;
    background: none;
    font: inherit;
    font-size: .9rem;
    font-weight: 600;
    color: var(--text);
    cursor: pointer;
    transition: background .15s;
}
.nav-category-btn:hover { background: var(--bg); }
.nav-category-btn .chevron {
    margin-left: auto;
    font-size: .7rem;
    transition: transform .2s;
}
.nav-category-btn.open .chevron { transform: rotate(180deg); }

.nav-items {
    display: none;
    padding-bottom: .25rem;
}
.nav-items.open { display: block; }

.nav-item {
    display: flex;
    align-items: center;
    gap: .5rem;
    padding: .45rem 1.4rem .45rem 2.6rem;
    font-size: .85rem;
    color: var(--text-light);
    transition: background .15s, color .15s;
}
.nav-item:hover, .nav-item.active {
    background: #eef1ff;
    color: var(--primary);
}

/* ── Main Content ─────────────────────────────── */
.main-content {
    flex: 1;
    margin-left: var(--sidebar-w);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

.top-bar {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: .8rem 1.5rem;
    display: flex;
    align-items: center;
    gap: 1rem;
    position: sticky;
    top: 0;
    z-index: 50;
}
.top-title { font-weight: 600; font-size: 1.05rem; }
.menu-btn {
    display: none;
    border: none;
    background: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text);
}

.content-area {
    flex: 1;
    padding: 2rem;
    max-width: 1100px;
    width: 100%;
    margin: 0 auto;
}

.overlay {
    display: none;
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,.3);
    z-index: 90;
}

/* ── Buttons ──────────────────────────────────── */
.btn {
    display: inline-flex;
    align-items: center;
    gap: .4rem;
    padding: .55rem 1.2rem;
    border: none;
    border-radius: var(--radius);
    font: inherit;
    font-size: .9rem;
    font-weight: 500;
    cursor: pointer;
    transition: background .15s, transform .1s;
}
.btn:active { transform: scale(.97); }
.btn-primary { background: var(--primary); color: #fff; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-success { background: var(--success); color: #fff; }
.btn-success:hover { background: #27b0a3; }
.btn-small { padding: .3rem .7rem; font-size: .8rem; background: var(--bg); color: var(--text); }
.btn-small:hover { background: var(--border); }

/* ── Home Page ────────────────────────────────── */
.home-hero {
    text-align: center;
    padding: 2rem 0 2.5rem;
}
.home-hero h1 { font-size: 2rem; margin-bottom: .4rem; }
.home-hero p { color: var(--text-light); font-size: 1.05rem; }

.category-section { margin-bottom: 2rem; }
.category-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: .8rem;
    display: flex;
    align-items: center;
    gap: .5rem;
    color: var(--text);
}

.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: .8rem;
}

.tool-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem 1.2rem;
    transition: border-color .15s, box-shadow .15s;
    display: flex;
    align-items: flex-start;
    gap: .8rem;
}
.tool-card:hover {
    border-color: var(--primary);
    box-shadow: var(--shadow);
}
.tool-card .card-icon {
    font-size: 1.4rem;
    color: var(--primary);
    flex-shrink: 0;
    margin-top: .1rem;
}
.tool-card .card-body h3 { font-size: .95rem; font-weight: 600; margin-bottom: .15rem; }
.tool-card .card-body p { font-size: .8rem; color: var(--text-light); line-height: 1.35; }

/* ── Tool Page ────────────────────────────────── */
.tool-page { max-width: 700px; }
.tool-header { margin-bottom: 1.5rem; }
.tool-header h1 { font-size: 1.5rem; margin-bottom: .3rem; }
.tool-header p { color: var(--text-light); }

.tool-notes {
    background: #fff8e1;
    border-left: 3px solid #f5b700;
    border-radius: 4px;
    padding: .75rem 1rem;
    margin-bottom: 1.25rem;
    font-size: .88rem;
    line-height: 1.5;
    color: #5a4200;
}
.tool-notes p { margin: 0 0 .5rem; }
.tool-notes p:last-child { margin-bottom: 0; }
.tool-notes code {
    background: rgba(0,0,0,.06);
    padding: .1rem .35rem;
    border-radius: 3px;
    font-size: .82rem;
}
.tool-notes details { margin-top: .5rem; }
.tool-notes details > summary {
    cursor: pointer;
    font-weight: 600;
    color: #8a6300;
}
.tool-notes details[open] > summary { margin-bottom: .5rem; }
.tool-notes ol, .tool-notes ul { margin: .25rem 0 .5rem 1.2rem; padding: 0; }
.tool-notes li { margin-bottom: .2rem; }
.tool-notes a { color: #b26f00; }

/* ── Upload Zone ──────────────────────────────── */
.upload-zone {
    border: 2px dashed var(--border);
    border-radius: var(--radius);
    padding: 2rem;
    text-align: center;
    cursor: pointer;
    transition: border-color .2s, background .2s;
    position: relative;
    margin-bottom: 1rem;
}
.upload-zone:hover, .upload-zone.dragover {
    border-color: var(--primary);
    background: #f0f3ff;
}
.upload-zone input[type="file"] {
    position: absolute;
    inset: 0;
    opacity: 0;
    cursor: pointer;
}
.upload-prompt i { font-size: 2.5rem; color: var(--primary); }
.upload-prompt p { font-size: 1rem; font-weight: 500; margin: .5rem 0 .2rem; }
.upload-prompt span { font-size: .85rem; color: var(--text-light); }
.upload-prompt small { display: block; margin-top: .4rem; font-size: .75rem; color: var(--text-light); }

.file-list { text-align: left; margin-top: .5rem; }
.file-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: .35rem .6rem;
    background: var(--bg);
    border-radius: 4px;
    font-size: .85rem;
    margin-bottom: .3rem;
}
.file-item .remove-file {
    border: none;
    background: none;
    color: var(--danger);
    cursor: pointer;
    font-size: 1rem;
}

/* ── Form Elements ────────────────────────────── */
.tool-options { margin-bottom: 1rem; }
.form-group { margin-bottom: .8rem; }
.form-group label {
    display: block;
    font-size: .85rem;
    font-weight: 500;
    margin-bottom: .3rem;
}

input[type="text"],
input[type="number"],
input[type="password"],
select,
textarea {
    width: 100%;
    padding: .5rem .7rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    font: inherit;
    font-size: .9rem;
    background: var(--surface);
    transition: border-color .15s;
}
input:focus, select:focus, textarea:focus {
    outline: none;
    border-color: var(--primary);
}
textarea { resize: vertical; }

.text-input { min-height: 100px; }

.checkbox-label, .radio-label {
    display: inline-flex;
    align-items: center;
    gap: .4rem;
    font-size: .9rem;
    cursor: pointer;
}
.radio-group { display: flex; gap: 1rem; flex-wrap: wrap; }

.range-group { display: flex; align-items: center; gap: .8rem; }
.range-group input[type="range"] { flex: 1; }
.range-value { font-size: .85rem; font-weight: 600; min-width: 3rem; }

/* ── Results ──────────────────────────────────── */
.result-area { margin-top: 1.5rem; }
.result-success, .result-error {
    display: flex;
    align-items: center;
    gap: .6rem;
    padding: 1rem;
    border-radius: var(--radius);
    font-size: .95rem;
    flex-wrap: wrap;
}
.result-success {
    background: #e8faf8;
    color: #1a7a6d;
}
.result-success .btn { margin-left: auto; }
.result-error {
    background: #fdeaea;
    color: var(--danger);
}
.result-text-box {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
}
.result-text-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: .5rem .8rem;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    font-size: .85rem;
    font-weight: 600;
}
.result-text-box pre {
    padding: .8rem;
    font-size: .85rem;
    max-height: 400px;
    overflow: auto;
    white-space: pre-wrap;
    word-break: break-word;
}

#result-preview { margin-top: .8rem; width: 100%; }
#result-preview img { max-width: 100%; border-radius: 6px; border: 1px solid var(--border); }

/* ── Spinner ──────────────────────────────────── */
.spin { animation: spin .8s linear infinite; display: inline-block; }
@keyframes spin { to { transform: rotate(360deg); } }

/* ── Client Tool Layouts ──────────────────────── */
.client-tool { max-width: 700px; }
.client-tool .tool-header { margin-bottom: 1.5rem; }
.client-tool .tool-header h1 { font-size: 1.5rem; margin-bottom: .3rem; }
.client-tool .tool-header p { color: var(--text-light); }

.split-pane {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 1rem;
}

.pane {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    overflow: hidden;
}
.pane-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: .5rem .8rem;
    background: var(--bg);
    border-bottom: 1px solid var(--border);
    font-size: .85rem;
    font-weight: 600;
}
.pane-body { padding: .8rem; }
.pane-body textarea {
    width: 100%;
    border: none;
    resize: vertical;
    min-height: 250px;
    font-family: "Consolas", "Monaco", monospace;
    font-size: .85rem;
    outline: none;
}
.pane-body pre {
    min-height: 250px;
    font-size: .85rem;
    white-space: pre-wrap;
    word-break: break-word;
    margin: 0;
}

/* ── Calculator ───────────────────────────────── */
.calc-display {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem;
    text-align: right;
    margin-bottom: 1rem;
}
.calc-expression { font-size: .85rem; color: var(--text-light); min-height: 1.2em; }
.calc-result { font-size: 2rem; font-weight: 600; word-break: break-all; }

.calc-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: .5rem;
}
.calc-btn {
    padding: .8rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--surface);
    font: inherit;
    font-size: 1.1rem;
    cursor: pointer;
    transition: background .1s;
}
.calc-btn:hover { background: var(--bg); }
.calc-btn.op { background: #eef1ff; color: var(--primary); font-weight: 600; }
.calc-btn.op:hover { background: #dde3ff; }
.calc-btn.eq { background: var(--primary); color: #fff; }
.calc-btn.eq:hover { background: var(--primary-dark); }
.calc-btn.span2 { grid-column: span 2; }

/* ── Converter Rows ───────────────────────────── */
.converter-row {
    display: flex;
    gap: .8rem;
    align-items: flex-end;
    margin-bottom: .8rem;
}
.converter-row .form-group { flex: 1; margin-bottom: 0; }
.converter-swap {
    padding: .5rem;
    border: 1px solid var(--border);
    border-radius: 6px;
    background: var(--surface);
    cursor: pointer;
    font-size: 1.2rem;
    align-self: flex-end;
    margin-bottom: .1rem;
}
.converter-swap:hover { background: var(--bg); }

/* ── Color Converter ──────────────────────────── */
.color-preview {
    width: 100%;
    height: 80px;
    border-radius: var(--radius);
    border: 1px solid var(--border);
    margin-bottom: 1rem;
    background: #4361ee;
}
.color-inputs { display: grid; grid-template-columns: 1fr 1fr; gap: .8rem; }

/* ── Percentage / Date Calc ───────────────────── */
.calc-section {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.2rem;
    margin-bottom: 1rem;
}
.calc-section h3 { font-size: .95rem; margin-bottom: .8rem; }
.calc-result-inline {
    font-size: 1.3rem;
    font-weight: 600;
    color: var(--primary);
    margin-top: .5rem;
}
.inline-form {
    display: flex;
    align-items: center;
    gap: .5rem;
    flex-wrap: wrap;
}
.inline-form input, .inline-form select { width: auto; flex: 0 0 auto; }
.inline-form .wide { flex: 1; min-width: 100px; }
.inline-form span { font-size: .9rem; white-space: nowrap; }

/* ── Markdown Preview ─────────────────────────── */
.md-preview {
    padding: .8rem;
    min-height: 250px;
    line-height: 1.6;
}
.md-preview h1, .md-preview h2, .md-preview h3 { margin: .8em 0 .4em; }
.md-preview h1 { font-size: 1.5rem; }
.md-preview h2 { font-size: 1.25rem; }
.md-preview h3 { font-size: 1.1rem; }
.md-preview p { margin-bottom: .6em; }
.md-preview code {
    background: var(--bg);
    padding: .15em .4em;
    border-radius: 3px;
    font-size: .9em;
}
.md-preview pre {
    background: var(--bg);
    padding: .8rem;
    border-radius: 6px;
    overflow-x: auto;
}
.md-preview pre code { background: none; padding: 0; }
.md-preview ul, .md-preview ol { padding-left: 1.5em; margin-bottom: .6em; }
.md-preview blockquote {
    border-left: 3px solid var(--primary);
    padding-left: .8rem;
    color: var(--text-light);
    margin: .6em 0;
}
.md-preview table { border-collapse: collapse; width: 100%; margin: .6em 0; }
.md-preview th, .md-preview td { border: 1px solid var(--border); padding: .4rem .6rem; text-align: left; }
.md-preview th { background: var(--bg); font-weight: 600; }

/* ── Responsive ───────────────────────────────── */
@media (max-width: 768px) {
    .sidebar { transform: translateX(-100%); }
    .sidebar.open { transform: translateX(0); }
    .overlay.open { display: block; }
    .main-content { margin-left: 0; }
    .menu-btn { display: block; }
    .split-pane { grid-template-columns: 1fr; }
    .color-inputs { grid-template-columns: 1fr; }
    .tools-grid { grid-template-columns: repeat(auto-fill, minmax(180px, 1fr)); }
    .content-area { padding: 1rem; }
    .converter-row { flex-direction: column; }
    .inline-form input, .inline-form select { width: 100%; }
}