:root {
    /* Colors - Dark Mode Default */
    --bg-color: #121212;
    --surface-color: #1e1e1e;
    --primary-color: #bb86fc;
    --secondary-color: #03dac6;
    --text-primary: #ffffff;
    --text-secondary: #b3b3b3;
    --error-color: #cf6679;
    
    /* Spacing */
    --spacing-sm: 8px;
    --spacing-md: 16px;
    --spacing-lg: 24px;
    
    /* Border Radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    --radius-lg: 16px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* Layout */
.app-container {
    max-width: 800px;
    margin: 0 auto;
    padding-bottom: 80px; /* Space for potential bottom nav or just aesthetic */
    min-height: 100vh;
}

/* Header */
header {
    background-color: var(--surface-color);
    padding: var(--spacing-md);
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}

header h1 {
    font-size: 1.25rem;
    font-weight: 700;
    color: var(--text-primary);
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-primary);
    font-size: 1.5rem;
    cursor: pointer;
    padding: var(--spacing-sm);
}

/* Auth Screens */
.auth-container {
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    height: 90vh;
    padding: var(--spacing-lg);
}

.input-group {
    width: 100%;
    margin-bottom: var(--spacing-md);
}

input {
    width: 100%;
    padding: 12px;
    background-color: var(--surface-color);
    border: 1px solid #333;
    border-radius: var(--radius-md);
    color: var(--text-primary);
    font-size: 1rem;
    transition: border-color var(--transition-fast);
}

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

button.primary-btn {
    width: 100%;
    padding: 14px;
    background-color: var(--primary-color);
    color: #000;
    font-weight: 600;
    border: none;
    border-radius: var(--radius-md);
    cursor: pointer;
    font-size: 1rem;
    transition: opacity var(--transition-fast);
}

button.primary-btn:active {
    opacity: 0.8;
}

/* Lists and Cards */
.article-list {
    padding: var(--spacing-md);
    list-style: none;
}

.article-card {
    background-color: var(--surface-color);
    padding: var(--spacing-md);
    border-radius: var(--radius-md);
    margin-bottom: var(--spacing-md);
    transition: transform var(--transition-fast);
    cursor: pointer;
}

.article-card:active {
    transform: scale(0.98);
}

.article-title {
    font-size: 1.1rem;
    font-weight: 600;
    margin-bottom: var(--spacing-sm);
    color: var(--primary-color);
}

.article-meta {
    font-size: 0.85rem;
    color: var(--text-secondary);
    display: flex;
    gap: var(--spacing-sm);
    flex-wrap: wrap;
}

.tag {
    background-color: rgba(187, 134, 252, 0.1);
    color: var(--primary-color);
    padding: 2px 8px;
    border-radius: var(--radius-sm);
    font-size: 0.75rem;
}

/* Article Detail */
.article-detail {
    padding: var(--spacing-lg);
    animation: fadeIn 0.3s ease;
}

.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-md);
    cursor: pointer;
}

.content-body {
    margin-top: var(--spacing-md);
    line-height: 1.8;
}

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

.error-msg {
    color: var(--error-color);
    margin-bottom: var(--spacing-md);
    font-size: 0.9rem;
    text-align: center;
}

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