/* =============================================
   LINGUAAI DESIGN SYSTEM — FOUNDATION v1.0
   ============================================= */

/* 
 * ROOT NAMESPACE FOR DESIGN TOKENS
 * Since LinguaAI modules have different root wrappers (e.g., #linguaai-app, #linguaai-vocab-v2, #linguaai-sentence-practice),
 * there is currently no single universal root. 
 * Therefore, tokens are scoped under .lai-design-system to prevent global bleed.
 * A future migration should wrap all modules in <div class="lai-design-system">.
 */
.lai-design-system {
    /* --- SPACING TOKENS --- */
    --lai-space-1: 4px;
    --lai-space-2: 8px;
    --lai-space-3: 12px;
    --lai-space-4: 16px;
    --lai-space-5: 24px;
    --lai-space-6: 32px;
    --lai-space-7: 48px;

    /* --- TYPOGRAPHY TOKENS (Mobile First, rem based) --- */
    --lai-font-size-xs: 0.75rem;       /* 12px */
    --lai-font-size-sm: 0.875rem;      /* 14px */
    --lai-font-size-body: 1rem;        /* 16px */
    --lai-font-size-subtitle: 1.125rem;/* 18px */
    --lai-font-size-title: 1.5rem;     /* 24px */
    --lai-font-size-page-title: 1.75rem;/* 28px */

    /* --- LINE HEIGHT TOKENS --- */
    --lai-line-height-tight: 1.2;
    --lai-line-height-normal: 1.5;
    --lai-line-height-relaxed: 1.75;

    /* --- RADIUS TOKENS --- */
    --lai-radius-sm: 8px;
    --lai-radius-md: 12px;
    --lai-radius-lg: 16px;
    --lai-radius-pill: 50px;

    /* --- SHADOW TOKENS --- */
    --lai-shadow-sm: 0 4px 12px rgba(0, 0, 0, 0.03);
    --lai-shadow-md: 0 8px 25px rgba(0, 0, 0, 0.04);
    --lai-shadow-focus: 0 0 0 4px rgba(79, 70, 229, 0.1);

    /* --- TOUCH TARGET --- */
    --lai-touch-target-min: 44px;

    /* --- LAYOUT TOKENS --- */
    --lai-content-max-width: 1100px;
    --lai-mobile-page-padding: var(--lai-space-4);
    --lai-tablet-page-padding: var(--lai-space-5);
    --lai-desktop-page-padding: var(--lai-space-6);

    /* --- Z-INDEX SCALE --- */
    --lai-z-base: 1;
    --lai-z-sticky: 100;
    --lai-z-header: 200;
    --lai-z-dropdown: 300;
    --lai-z-modal: 400;
    --lai-z-toast: 500;

    /* --- SEMANTIC COLOR TOKENS --- */
    --lai-color-primary: #4f46e5;
    --lai-color-primary-hover: #4338ca;
    --lai-color-secondary: #3b82f6;
    --lai-color-background: #f8fafc;
    --lai-color-surface: #ffffff;
    --lai-color-surface-muted: #f1f5f9;
    --lai-color-text: #334155;
    --lai-color-text-muted: #64748b;
    --lai-color-border: #e2e8f0;
    --lai-color-success: #10b981;
    --lai-color-warning: #f59e0b;
    --lai-color-error: #ef4444;
    --lai-color-focus: rgba(79, 70, 229, 0.25);
}

/* =============================================
   VIEWPORT & SAFE AREA HELPERS
   ============================================= */
.lai-min-screen {
    min-height: 100vh;
}
@supports (min-height: 100dvh) {
    .lai-min-screen {
        min-height: 100dvh;
    }
}

.lai-page-shell {
    box-sizing: border-box;
    max-width: 100%;
    /* overflow behavior controlled per-component */
}

/* Safe area padding classes */
.lai-safe-top {
    padding-top: env(safe-area-inset-top, 0);
}

.lai-safe-bottom {
    padding-bottom: env(safe-area-inset-bottom, 0);
}

.lai-scroll-region {
    overflow-y: auto;
    overflow-x: hidden;
    -webkit-overflow-scrolling: touch;
}

/* =============================================
   TYPOGRAPHY HELPERS
   ============================================= */
.lai-text-xs { font-size: var(--lai-font-size-xs); line-height: var(--lai-line-height-normal); }
.lai-text-sm { font-size: var(--lai-font-size-sm); line-height: var(--lai-line-height-normal); }
.lai-text-body { font-size: var(--lai-font-size-body); line-height: var(--lai-line-height-normal); }
.lai-text-subtitle { font-size: var(--lai-font-size-subtitle); line-height: var(--lai-line-height-tight); font-weight: 600; }
.lai-text-title { font-size: var(--lai-font-size-title); line-height: var(--lai-line-height-tight); font-weight: 700; }
.lai-text-page-title { font-size: var(--lai-font-size-page-title); line-height: var(--lai-line-height-tight); font-weight: 800; }

.lai-text-muted { color: var(--lai-color-text-muted); }

/* Utility to support very long words without breaking layouts */
.lai-text-break {
    overflow-wrap: anywhere;
    word-break: normal;
}

/* =============================================
   SPACING & LAYOUT HELPERS
   ============================================= */
.lai-stack {
    display: flex;
    flex-direction: column;
    gap: var(--lai-space-4);
}

.lai-cluster {
    display: flex;
    flex-wrap: wrap;
    gap: var(--lai-space-3);
    align-items: center;
}

.lai-grid {
    display: grid;
    gap: var(--lai-space-4);
}

.lai-full-width {
    width: 100%;
    max-width: 100%;
}

.lai-container {
    width: 100%;
    max-width: var(--lai-content-max-width);
    margin-inline: auto;
}

.lai-page-padding {
    padding-inline: var(--lai-mobile-page-padding);
}
@media (min-width: 768px) {
    .lai-page-padding {
        padding-inline: var(--lai-tablet-page-padding);
    }
}
@media (min-width: 1024px) {
    .lai-page-padding {
        padding-inline: var(--lai-desktop-page-padding);
    }
}

/* =============================================
   BUTTON FOUNDATION
   ============================================= */
.lai-button {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: var(--lai-touch-target-min);
    padding-inline: var(--lai-space-5);
    padding-block: var(--lai-space-2);
    box-sizing: border-box;
    max-width: 100%;
    border-radius: var(--lai-radius-md);
    font-size: var(--lai-font-size-body);
    font-weight: 600;
    line-height: var(--lai-line-height-tight);
    text-align: center;
    cursor: pointer;
    border: 1px solid transparent;
    transition: all 0.2s ease;
}

.lai-button:focus-visible {
    outline: none;
    box-shadow: var(--lai-shadow-focus);
}

.lai-button:disabled,
.lai-button[aria-disabled="true"] {
    opacity: 0.6;
    cursor: not-allowed;
}

.lai-button--primary {
    background-color: var(--lai-color-primary);
    color: var(--lai-color-surface);
}
.lai-button--primary:hover:not(:disabled) {
    background-color: var(--lai-color-primary-hover);
}

.lai-button--secondary {
    background-color: var(--lai-color-surface-muted);
    color: var(--lai-color-text);
}
.lai-button--secondary:hover:not(:disabled) {
    background-color: var(--lai-color-border);
}

.lai-button--ghost {
    background-color: transparent;
    color: var(--lai-color-primary);
}
.lai-button--ghost:hover:not(:disabled) {
    background-color: var(--lai-color-surface-muted);
}

.lai-button--danger {
    background-color: var(--lai-color-error);
    color: var(--lai-color-surface);
}

.lai-button--full {
    width: 100%;
}

/* =============================================
   CARD FOUNDATION
   ============================================= */
.lai-card {
    background-color: var(--lai-color-surface);
    border-radius: var(--lai-radius-lg);
    box-shadow: var(--lai-shadow-sm);
    box-sizing: border-box;
    max-width: 100%;
    display: flex;
    flex-direction: column;
}

.lai-card--interactive {
    transition: transform 0.2s ease, box-shadow 0.2s ease;
    cursor: pointer;
}
.lai-card--interactive:hover {
    transform: translateY(-2px);
    box-shadow: var(--lai-shadow-md);
}

.lai-card__header,
.lai-card__body,
.lai-card__footer {
    padding: var(--lai-space-5);
}

.lai-card--compact .lai-card__header,
.lai-card--compact .lai-card__body,
.lai-card--compact .lai-card__footer {
    padding: var(--lai-space-3);
}

/* =============================================
   RTL FOUNDATION
   Logical Properties are already used above (padding-inline, margin-inline).
   Only minimal explicit overrides if logical properties are not enough.
   ============================================= */
html[dir="rtl"] .lai-design-system,
[dir="rtl"] .lai-design-system {
    text-align: start;
}