:root {
    --bg-color: #0A1A1A;
    --primary-color: #00CEC9;
    --secondary-color: #81ECEC;
    --accent-color: #E17055;
    --text-primary: #FFFFFF;
    --text-secondary: #B2BEC3;
    --border-color: rgba(255, 255, 255, 0.1);
    --surface-color: rgba(255, 255, 255, 0.05);
    --border-radius: 12px;
    --transition: all 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

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

body {
    font-family: 'Inter', system-ui, -apple-system, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

/* App Container */
.app-container {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

/* Header */
.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1.5rem;
    background: rgba(10, 26, 26, 0.8);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-bottom: 1px solid var(--border-color);
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.25rem;
    font-weight: 800;
    color: var(--primary-color);
    letter-spacing: -0.02em;
}

.logo i {
    stroke-width: 2.5px;
}

.toolbar {
    display: flex;
    gap: 0.75rem;
}

.btn {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    padding: 0.6rem 1.2rem;
    border-radius: 10px;
    font-size: 0.875rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    border: 1px solid transparent;
    user-select: none;
}

.btn-primary {
    background-color: var(--primary-color);
    color: var(--bg-color);
    box-shadow: 0 4px 14px rgba(0, 206, 201, 0.2);
}

.btn-primary:hover {
    background-color: var(--secondary-color);
    transform: translateY(-1px);
    box-shadow: 0 6px 20px rgba(0, 206, 201, 0.3);
}

.btn-ghost {
    background-color: var(--surface-color);
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-ghost:hover {
    background-color: rgba(255, 255, 255, 0.1);
    border-color: var(--secondary-color);
}

/* Main Content */
.editor-main {
    flex: 1;
    overflow: hidden;
    position: relative;
}

.pane-container {
    display: flex;
    height: 100%;
    width: 100%;
}

.pane {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 0;
    position: relative;
}

.pane-header {
    padding: 0.6rem 1.5rem;
    background: rgba(0, 0, 0, 0.3);
    border-bottom: 1px solid var(--border-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
}

.pane-title {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    font-size: 0.7rem;
    text-transform: uppercase;
    letter-spacing: 0.1em;
    font-weight: 700;
    color: var(--text-secondary);
}

.pane-title i {
    width: 14px;
    height: 14px;
    color: var(--primary-color);
}

/* Editor Area */
#markdown-input {
    flex: 1;
    background: transparent;
    border: none;
    color: var(--text-primary);
    padding: 2rem;
    font-family: 'JetBrains Mono', 'Menlo', 'Monaco', 'Courier New', monospace;
    font-size: 1.05rem;
    line-height: 1.7;
    resize: none;
    outline: none;
    width: 100%;
    caret-color: var(--primary-color);
}

/* Preview Area */
#preview-output {
    flex: 1;
    padding: 2rem 3rem;
    overflow-y: auto;
    background: rgba(0, 0, 0, 0.15);
}

/* Resizer Bar */
.resizer {
    width: 6px;
    background: var(--bg-color);
    position: relative;
    cursor: col-resize;
    z-index: 10;
}

.resizer::after {
    content: '';
    position: absolute;
    left: 2px;
    top: 0;
    bottom: 0;
    width: 2px;
    background: var(--border-color);
    transition: var(--transition);
}

.resizer:hover::after, .resizer:active::after {
    background: var(--primary-color);
    box-shadow: 0 0 10px var(--primary-color);
}

/* Footer */
.app-footer {
    padding: 0.6rem 1.5rem;
    background: var(--surface-color);
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 0.75rem;
    color: var(--text-secondary);
    z-index: 100;
}

.stats {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.separator {
    color: var(--border-color);
}

.status {
    display: flex;
    gap: 0.5rem;
}

.badge {
    padding: 3px 10px;
    background: rgba(0, 206, 201, 0.1);
    color: var(--primary-color);
    border-radius: 100px;
    font-weight: 600;
    font-size: 0.65rem;
    text-transform: uppercase;
}

/* Markdown Typography */
.markdown-body {
    line-height: 1.8;
    color: #e6edf3;
    font-size: 1.1rem;
}

.markdown-body h1, .markdown-body h2, .markdown-body h3,
.markdown-body h4, .markdown-body h5, .markdown-body h6 {
    margin-top: 2rem;
    margin-bottom: 1.25rem;
    font-weight: 700;
    line-height: 1.25;
    color: var(--primary-color);
}

.markdown-body h1 { font-size: 2.25rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--border-color); }
.markdown-body h2 { font-size: 1.75rem; padding-bottom: 0.4rem; border-bottom: 1px solid var(--border-color); }
.markdown-body h3 { font-size: 1.5rem; }

.markdown-body p { margin-bottom: 1.25rem; }

.markdown-body a {
    color: var(--secondary-color);
    text-decoration: none;
    border-bottom: 1px solid transparent;
    transition: var(--transition);
}

.markdown-body a:hover {
    border-bottom-color: var(--secondary-color);
}

.markdown-body code {
    background: var(--surface-color);
    padding: 0.2rem 0.5rem;
    border-radius: 6px;
    font-family: 'JetBrains Mono', monospace;
    font-size: 0.9em;
    color: var(--secondary-color);
}

.markdown-body pre {
    background: #050d0d;
    padding: 1.5rem;
    border-radius: 12px;
    overflow-x: auto;
    margin-bottom: 1.5rem;
    border: 1px solid var(--border-color);
}

.markdown-body pre code {
    background: transparent;
    padding: 0;
    color: inherit;
    font-size: 0.95rem;
}

.markdown-body blockquote {
    border-left: 4px solid var(--primary-color);
    padding: 0.5rem 0 0.5rem 1.5rem;
    color: var(--text-secondary);
    background: rgba(0, 206, 201, 0.03);
    border-top-right-radius: 8px;
    border-bottom-right-radius: 8px;
    margin: 1.5rem 0;
}

.markdown-body img {
    max-width: 100%;
    border-radius: 12px;
    box-shadow: 0 10px 30px rgba(0,0,0,0.3);
}

.markdown-body ul, .markdown-body ol {
    margin-bottom: 1.5rem;
    padding-left: 2rem;
}

.markdown-body li {
    margin-bottom: 0.5rem;
}

.markdown-body table {
    width: 100%;
    border-collapse: collapse;
    margin-bottom: 1.5rem;
    border-radius: 8px;
    overflow: hidden;
}

.markdown-body th, .markdown-body td {
    border: 1px solid var(--border-color);
    padding: 0.75rem 1rem;
    text-align: left;
}

.markdown-body th {
    background: rgba(0, 206, 201, 0.1);
    color: var(--primary-color);
}

.markdown-body tr:nth-child(even) {
    background: rgba(255, 255, 255, 0.02);
}

/* Scrollbar Customization */
::-webkit-scrollbar {
    width: 10px;
    height: 10px;
}

::-webkit-scrollbar-track {
    background: transparent;
}

::-webkit-scrollbar-thumb {
    background: rgba(255, 255, 255, 0.1);
    border-radius: 20px;
    border: 3px solid transparent;
    background-clip: content-box;
}

::-webkit-scrollbar-thumb:hover {
    background-color: var(--primary-color);
}

/* Fullscreen Mode (Focused Writing) */
body.fullscreen .app-header,
body.fullscreen .app-footer {
    display: none;
}

body.fullscreen .editor-main {
    height: 100vh;
}

body.fullscreen .pane-container {
    max-width: 1200px;
    margin: 0 auto;
}

/* Exit Fullscreen Button (floating) */
#exit-fullscreen-btn {
    display: none;
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    z-index: 1000;
}

body.fullscreen #exit-fullscreen-btn {
    display: flex;
}

/* Mobile Adjustments */
@media (max-width: 768px) {
    .pane-container {
        flex-direction: column;
    }

    .resizer {
        width: 100%;
        height: 8px;
        cursor: row-resize;
    }

    .resizer::after {
        left: 0;
        right: 0;
        top: 3px;
        bottom: auto;
        width: auto;
        height: 2px;
    }

    .btn span {
        display: none;
    }

    .logo span {
        font-size: 1rem;
    }

    #preview-output {
        padding: 1.5rem;
    }
}