/* ============================================================
   Technofox-Todo - Design System Foundations
   Modern, sober, premium visual identity
   Loaded BEFORE todo.css to establish variables and base styles
   ============================================================ */

:root {
    /* --- Core Palette --- */
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-app: #f8fafc;
    --bg-surface: #ffffff;
    --bg-subtle: #f1f5f9;

    /* --- Text Colors --- */
    --text-primary: #0f172a;
    --text-secondary: #64748b;
    --text-tertiary: #94a3b8;
    --text-inverse: #f8fafc;
    --text-accent: #ff9b00;

    /* --- Accent Colors (Technofox identity) --- */
    --accent: #ff9b00;
    --accent-hover: #ed6b21;
    --accent-subtle: rgba(255, 155, 0, 0.1);
    --accent-border: rgba(255, 155, 0, 0.3);

    /* --- Semantic Colors --- */
    --success: #16a34a;
    --success-subtle: #dcfce7;
    --warning: #d97706;
    --warning-subtle: #fef3c7;
    --danger: #dc2626;
    --danger-subtle: #fee2e2;
    --info: #2563eb;
    --info-subtle: #dbeafe;

    /* --- Borders & Surfaces --- */
    --border-color: #e2e8f0;
    --border-strong: #cbd5e1;
    --border-focus: #ff9b00;

    /* --- Radius System --- */
    --radius-sm: 6px;
    --radius-md: 10px;
    --radius-lg: 14px;
    --radius-xl: 20px;
    --radius-full: 9999px;

    /* --- Shadow System (subtle, layered) --- */
    --shadow-xs: 0 1px 2px rgba(15, 23, 42, 0.06);
    --shadow-sm: 0 1px 3px rgba(15, 23, 42, 0.1), 0 1px 2px rgba(15, 23, 42, 0.04);
    --shadow-md: 0 4px 6px -1px rgba(15, 23, 42, 0.1), 0 2px 4px -2px rgba(15, 23, 42, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(15, 23, 42, 0.1), 0 4px 6px -4px rgba(15, 23, 42, 0.05);
    --shadow-xl: 0 20px 25px -5px rgba(15, 23, 42, 0.12), 0 8px 10px -6px rgba(15, 23, 42, 0.06);

    /* --- Spacing System (4px base) --- */
    --spacing-1: 4px;
    --spacing-2: 8px;
    --spacing-3: 12px;
    --spacing-4: 16px;
    --spacing-5: 20px;
    --spacing-6: 24px;
    --spacing-8: 32px;

    /* --- Typography --- */
    --font-stack: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
    --font-size-xs: 0.75rem;
    --font-size-sm: 0.8125rem;
    --font-size-md: 0.875rem;
    --font-size-lg: 1rem;
    --font-size-xl: 1.25rem;
    --font-size-2xl: 1.5rem;

    /* --- Transitions --- */
    --transition-fast: 150ms ease;
    --transition-base: 200ms ease;
    --transition-slow: 300ms ease;

    /* --- Z-index scale --- */
    --z-dropdown: 1000;
    --z-sticky: 1020;
    --z-modal-backdrop: 1040;
    --z-modal: 1050;
    --z-toast: 1060;
}

body {
    background: var(--bg-app);
    color: var(--text-primary);
    font-family: var(--font-stack);
    font-size: var(--font-size-md);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
    padding: var(--spacing-5);
}

/* --- Global button base (used across all pages) --- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: var(--spacing-2);
    padding: var(--spacing-3) var(--spacing-4);
    border: 1px solid transparent;
    border-radius: var(--radius-md);
    font-family: var(--font-stack);
    font-size: var(--font-size-md);
    font-weight: 500;
    line-height: 1;
    cursor: pointer;
    transition: all var(--transition-fast);
    white-space: nowrap;
    text-decoration: none;
    user-select: none;
}

.btn:focus-visible {
    outline: 2px solid var(--border-focus);
    outline-offset: 2px;
}

.btn-primary {
    background: var(--accent);
    color: white;
}

.btn-primary:hover {
    background: var(--accent-hover);
    box-shadow: var(--shadow-sm);
}

.btn-primary:active {
    transform: translateY(1px);
}

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

.btn-secondary:hover {
    background: var(--bg-subtle);
    border-color: var(--border-strong);
}

.btn-danger {
    background: var(--danger);
    color: white;
}

.btn-danger:hover {
    background: #b91c1c;
    box-shadow: var(--shadow-sm);
}

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

.btn-warning:hover {
    background: #b45309;
}

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

.btn-success:hover {
    background: #15803d;
}

.btn-small {
    padding: var(--spacing-2) var(--spacing-3);
    font-size: var(--font-size-sm);
}

/* --- Accessible focus ring globally --- */
a:focus-visible,
input:focus-visible,
textarea:focus-visible,
select:focus-visible,
button:focus-visible {
    outline: 2px solid var(--border-focus);
    outline-offset: 2px;
}