/* ========================================================================
   Design Tokens — CSS Custom Properties
   ======================================================================== */
/* Breakpoints: --bp-md: 640px (tablet), --bp-lg: 1024px (desktop) */
:root {
    /* Color palette */
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-bg: #f8fafc;
    --color-surface: #ffffff;
    --color-surface-alt: #f1f5f9;
    --color-text: #1e293b;
    --color-text-muted: #64748b;
    --color-border: #e2e8f0;
    --color-nav-bg: #1e293b;
    --color-nav-text: #f1f5f9;
    --color-nav-hover-bg: #334155;
    /* Status colors */
    --color-status-green-bg: #dcfce7;
    --color-status-green-text: #166534;
    --color-status-yellow-bg: #fef9c3;
    --color-status-yellow-text: #854d0e;
    --color-status-red-bg: #fee2e2;
    --color-status-red-text: #991b1b;
    /* Spacing scale (4px base) */
    --space-1: 4px;
    --space-2: 8px;
    --space-3: 12px;
    --space-4: 16px;
    --space-5: 20px;
    --space-6: 24px;
    --space-8: 32px;
    --space-10: 40px;
    /* Border radius */
    --radius-sm: 4px;
    --radius-md: 8px;
    /* Box shadows */
    --shadow-md: 0 2px 8px rgba(0, 0, 0, 0.12);
}

/* ========================================================================
   Base & Reset
   ======================================================================== */
*,
*::before,
*::after {
    box-sizing: border-box;
}

body {
    margin: 0;
    padding: 0;
    background: var(--color-bg);
    color: var(--color-text);
    font: 16px/1.6 -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Arial, sans-serif;
}

h1,
h2,
h3 {
    line-height: 1.2;
    margin-top: 0;
}

a {
    color: var(--color-primary);
}

img {
    max-width: 100%;
    height: auto;
}

/* ========================================================================
   Layout — Container
   Mobile-first: full-width with padding; centered max-width on large screens.
   .page serves as the container for main content.
   ======================================================================== */
.page {
    width: 100%;
    padding: var(--space-6) var(--space-4);
}

@media screen and (min-width: 640px) {
    .page {
        padding: var(--space-6);
    }
}

@media screen and (min-width: 1024px) {
    .page {
        max-width: 1100px;
        margin-left: auto;
        margin-right: auto;
        padding: var(--space-8);
    }
}

/* ========================================================================
   Header
   ======================================================================== */
.header {
    text-align: center;
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    padding: var(--space-4);
}

.header h1 {
    font-size: 2rem;
    margin: 0;
    color: var(--color-primary);
}

.header p {
    margin: var(--space-1) 0 0;
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

/* ========================================================================
   Navigation — mobile-first, collapses to hamburger below 640px
   ======================================================================== */
.topnav {
    background-color: var(--color-nav-bg);
    min-height: 56px;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    padding: 0 var(--space-4);
}

/* Hamburger button — visible only on mobile */
.nav-toggle {
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    width: 28px;
    height: 20px;
    background: none;
    border: none;
    cursor: pointer;
    padding: 0;
    margin-left: auto;
}

.nav-toggle span {
    display: block;
    height: 2px;
    width: 100%;
    background: var(--color-nav-text);
    border-radius: 2px;
}

/* Nav links — hidden by default on mobile, shown as vertical stack when open */
.nav-links {
    display: none;
    flex-direction: column;
    width: 100%;
    padding: var(--space-2) 0;
    gap: var(--space-1);
}

.nav-links.nav-open {
    display: flex;
}

.nav-links a {
    color: var(--color-nav-text);
    text-decoration: none;
    padding: var(--space-3) var(--space-2);
    border-radius: var(--radius-sm);
    transition: background-color 0.15s;
}

.nav-links a:hover {
    background-color: var(--color-nav-hover-bg);
    color: var(--color-nav-text);
}

/* Desktop nav — always visible as flex row */
@media screen and (min-width: 640px) {
    .nav-toggle {
        display: none;
    }

    .nav-links {
        display: flex;
        flex-direction: row;
        width: auto;
        padding: 0;
        align-items: center;
        flex: 1;
    }

    .nav-links a {
        padding: var(--space-2) var(--space-3);
        white-space: nowrap;
    }

    .nav-user {
        margin-left: auto;
        display: flex;
        gap: var(--space-1);
    }
}

/* ========================================================================
   Footer
   ======================================================================== */
.footer {
    padding: var(--space-2) var(--space-4);
    text-align: center;
    color: var(--color-text-muted);
    font-size: 0.9rem;
}

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

/* ========================================================================
   Buttons
   ======================================================================== */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-sm);
    text-decoration: none;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    border: none;
    transition: background-color 0.15s;
}

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

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

.btn-secondary {
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

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

.btn-sm {
    padding: var(--space-1) var(--space-3);
    font-size: 0.8rem;
}

/* ========================================================================
   Month Calendar
   ======================================================================== */
.month td,
.month th {
    text-align: center;
    width: 4em;
    padding: var(--space-1);
}

.monthnav td {
    text-align: center;
}

table.month,
table.monthnav {
    width: fit-content;
    margin-left: auto;
    margin-right: auto;
}

/* Horizontal scroll wrapper — prevents page overflow on narrow screens */
.calendar-scroll {
    overflow-x: auto;
    -webkit-overflow-scrolling: touch;
}

/* ========================================================================
   Dashboard & Habit Cards
   ======================================================================== */
.dashboard {
    padding-top: var(--space-4);
}

.dashboard-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-5);
}

.dashboard-header h2 {
    margin: 0;
}

/* CSS Grid — cards fill available width; wraps into multiple columns on wider screens */
.habits-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: var(--space-5);
}

.habit-card {
    background: var(--color-surface);
    padding: var(--space-2) var(--space-4);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
}

.habit-card-header {
    display: flex;
    align-items: center;
    gap: var(--space-2);
    margin-bottom: var(--space-2);
}

.habit-card-header h3 {
    margin: 0;
    font-size: 1rem;
}

.habit-card-header h3 a {
    color: var(--color-text);
    text-decoration: none;
}

.habit-card-header h3 a:hover {
    text-decoration: underline;
}

.habit-description {
    color: var(--color-text-muted);
    font-size: 0.9rem;
    margin: 0 0 var(--space-4) 0;
}

.habit-card-actions {
    display: flex;
    gap: var(--space-2);
}

/* ========================================================================
   Badges
   ======================================================================== */
.badge {
    display: inline-block;
    font-size: 0.75rem;
    padding: 2px var(--space-2);
    border-radius: var(--radius-sm);
    font-weight: 500;
}

.badge-private {
    color: var(--color-text-muted);
    border: 1px solid var(--color-border);
}

/* ========================================================================
   Empty State
   ======================================================================== */
.empty-state {
    text-align: center;
    padding: var(--space-10);
    color: var(--color-text-muted);
}

.empty-state a {
    color: var(--color-primary);
    font-weight: 500;
}

/* ========================================================================
   Auth Forms
   ======================================================================== */
.auth-container {
    max-width: 420px;
    margin: var(--space-10) auto;
    padding: 0 var(--space-4);
}

.auth-container h2 {
    text-align: center;
    margin-bottom: var(--space-5);
}

.auth-form {
    background: var(--color-surface);
    padding: var(--space-8);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
}

.auth-error {
    background: var(--color-status-red-bg);
    color: var(--color-status-red-text);
    padding: var(--space-3) var(--space-4);
    border-radius: var(--radius-sm);
    margin-bottom: var(--space-5);
    border: 1px solid #fca5a5;
}

.form-group {
    margin-bottom: var(--space-5);
}

.form-group label {
    display: block;
    margin-bottom: var(--space-1);
    font-weight: 500;
    font-size: 0.9rem;
    color: var(--color-text);
}

.form-group input,
.form-group textarea {
    width: 100%;
    padding: var(--space-2) var(--space-3);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-size: 1rem;
    box-sizing: border-box;
    background: var(--color-surface);
    color: var(--color-text);
    transition: border-color 0.15s;
}

.form-group input:focus,
.form-group textarea:focus {
    outline: none;
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.12);
}

.auth-form button {
    width: 100%;
    padding: var(--space-3);
    background: var(--color-primary);
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.15s;
}

.auth-form button:hover {
    background: var(--color-primary-hover);
}

.auth-form button:disabled {
    background: var(--color-text-muted);
    cursor: not-allowed;
}

.auth-link {
    text-align: center;
    margin-top: var(--space-5);
    margin-bottom: 0;
}

.auth-link a {
    color: var(--color-primary);
    font-weight: 500;
}

.auth-divider {
    display: flex;
    align-items: center;
    margin: var(--space-5) 0;
}

.auth-divider::before,
.auth-divider::after {
    content: '';
    flex: 1;
    border-bottom: 1px solid var(--color-border);
}

.auth-divider span {
    padding: 0 var(--space-4);
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

.google-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: var(--space-2);
    width: 100%;
    padding: var(--space-3);
    background: var(--color-surface);
    color: var(--color-text);
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-size: 1rem;
    cursor: pointer;
    transition: background-color 0.15s;
}

.google-btn:hover {
}

.google-btn:disabled {
    cursor: not-allowed;
    opacity: 0.7;
}

.email-link-status {
    text-align: center;
    padding: var(--space-5) 0;
}

.email-link-status p {
    margin: var(--space-2) 0;
}

.email-link-hint {
    color: var(--color-text-muted);
    font-size: 0.875rem;
}

.email-link-success {
    background: var(--color-status-green-bg);
    color: var(--color-status-green-text);
    padding: var(--space-4);
    border-radius: var(--radius-sm);
    text-align: center;
    border: 1px solid #bbf7d0;
}

.email-link-success p {
    margin: var(--space-1) 0;
}

/* ========================================================================
   Profile Page
   ======================================================================== */
.profile-container {
    max-width: 540px;
    margin: var(--space-10) auto;
    padding: 0 var(--space-4);
}

.profile-card {
    background: var(--color-surface);
    padding: var(--space-8);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-md);
    border: 1px solid var(--color-border);
    margin-bottom: var(--space-5);
}

.profile-field {
    margin-bottom: var(--space-5);
}

.profile-field:last-child {
    margin-bottom: 0;
}

.profile-field label {
    display: block;
    font-weight: 500;
    color: var(--color-text-muted);
    font-size: 0.875rem;
    margin-bottom: var(--space-1);
}

.profile-field p {
    margin: 0;
    font-size: 1rem;
}

.profile-id {
    font-family: monospace;
    font-size: 0.875rem;
    color: var(--color-text-muted);
}

.profile-actions {
    text-align: center;
}