/* ========================================
   Trip Cost Sharing - Clean Modern Design
   ======================================== */

@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;600;700&display=swap');

:root {
    --bg: #f5f7fa;
    --bg-card: #ffffff;
    --bg-input: #f0f2f5;
    --bg-nav: #ffffff;
    --bg-header: #ffffff;
    --bg-overlay: rgba(0,0,0,0.45);

    --primary: #4f6ef7;
    --primary-light: #e8ecff;
    --primary-dark: #3b57d9;
    --success: #22c55e;
    --danger: #ef4444;
    --warning: #f59e0b;

    --text: #1e293b;
    --text-secondary: #64748b;
    --text-muted: #94a3b8;

    --border: #e2e8f0;
    --shadow: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.1);

    --radius: 12px;
    --radius-sm: 8px;
    --font: 'Inter', -apple-system, sans-serif;
    --nav-h: 60px;
    --header-h: 54px;
    --max-w: 560px;
}

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

html { font-size:16px; -webkit-text-size-adjust:100%; -webkit-tap-highlight-color:transparent; }

body {
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
    min-height: 100dvh;
    -webkit-font-smoothing: antialiased;
}

#app {
    max-width: var(--max-w);
    margin: 0 auto;
    min-height: 100dvh;
    background: var(--bg);
}

/* Header */
.app-header {
    position: sticky; top:0; z-index:100;
    background: var(--bg-header);
    border-bottom: 1px solid var(--border);
    padding: 0 16px;
    display: flex; align-items:center; justify-content:center; gap:8px;
    height: var(--header-h);
}
.app-header h1 { font-size:1.05rem; font-weight:700; color:var(--primary); }
.app-header .header-icon { width:20px; height:20px; stroke-width: 2.5; }

.btn-back {
    background:none; border:none; color:var(--primary); font-size:0.9rem;
    cursor:pointer; padding:4px; display:flex; align-items:center; gap:4px;
    font-family:var(--font); font-weight:500;
}
.btn-back span { font-size:1.1rem; }

/* Pages */
.page { display:none; padding:16px; padding-bottom:calc(var(--nav-h) + 32px); }
.page.active { display:block; animation: fadeIn .2s ease; }
@keyframes fadeIn { from{opacity:0;transform:translateY(4px)} to{opacity:1;transform:translateY(0)} }
@keyframes slideUp { from{opacity:0;transform:translateY(16px)} to{opacity:1;transform:translateY(0)} }

/* Bottom Nav */
.bottom-nav {
    position:fixed; bottom:0; left:50%; transform:translateX(-50%);
    width:100%; max-width:var(--max-w);
    background:var(--bg-nav); border-top:1px solid var(--border);
    display:flex; align-items:center; justify-content:space-around;
    height:var(--nav-h); z-index:200;
    padding-bottom:env(safe-area-inset-bottom,0);
    box-shadow: 0 -2px 8px rgba(0,0,0,0.04);
}
.nav-item {
    display:flex; flex-direction:column; align-items:center; gap:2px;
    padding:6px 16px; border:none; background:none;
    color:var(--text-muted); font-family:var(--font); font-size:0.65rem;
    font-weight:500; cursor:pointer; position:relative;
}
.nav-item .nav-icon { width:22px; height:22px; margin-bottom: 2px; stroke-width: 2; }
.nav-item.active { color:var(--primary); }
.nav-item.active::before {
    content:''; position:absolute; top:0; left:50%; transform:translateX(-50%);
    width:28px; height:3px; background:var(--primary); border-radius:0 0 3px 3px;
}

/* Cards */
.card {
    background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); padding:14px; margin-bottom:12px;
    box-shadow:var(--shadow); transition:box-shadow .2s;
}
.card:active { box-shadow:var(--shadow-md); }
.card-title { font-size:0.95rem; font-weight:600; margin-bottom:2px; }
.card-subtitle { font-size:0.8rem; color:var(--text-secondary); }
.card-meta { display:flex; gap:14px; margin-top:6px; font-size:0.75rem; color:var(--text-muted); }
.card-actions { display:flex; gap:6px; margin-top:10px; padding-top:8px; border-top:1px solid var(--border); }

/* Stats */
.stats-grid { display:grid; grid-template-columns:1fr 1fr; gap:12px; margin-bottom:20px; }
.stat-card {
    background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); padding:16px; text-align:center;
    box-shadow:var(--shadow);
}
.stat-value { font-size:1.8rem; font-weight:700; color:var(--primary); }
.stat-card:nth-child(2) .stat-value { color:var(--success); }
.stat-label { font-size:0.75rem; color:var(--text-secondary); margin-top:2px; font-weight:500; }

/* Section Title */
.section-title {
    font-size:0.8rem; font-weight:600; color:var(--text-secondary);
    text-transform:uppercase; letter-spacing:0.8px; margin-bottom:12px;
}

/* Buttons */
.btn {
    display:inline-flex; align-items:center; justify-content:center; gap:6px;
    padding:8px 14px; border:none; border-radius:var(--radius-sm);
    font-family:var(--font); font-size:0.85rem; font-weight:600;
    cursor:pointer; transition:opacity .15s;
}
.btn:active { opacity:0.8; transform:scale(0.97); }
.btn-primary { background:var(--primary); color:#fff; }
.btn-secondary { background:var(--bg-input); color:var(--text-secondary); border:1px solid var(--border); }
.btn-danger { background:var(--danger); color:#fff; }
.btn-success { background:var(--success); color:#fff; }
.btn-sm { padding:6px 10px; font-size:0.75rem; }
.btn-icon { width:34px; height:34px; padding:0; border-radius:var(--radius-sm); font-size:0.95rem; }

/* FAB */
.fab {
    position:fixed;
    bottom:calc(var(--nav-h) + 14px + env(safe-area-inset-bottom,0));
    right:calc(50% - var(--max-w)/2 + 16px);
    width:52px; height:52px; border-radius:50%;
    background:var(--primary); color:#fff; border:none;
    font-size:1.5rem; cursor:pointer;
    display:flex; align-items:center; justify-content:center;
    box-shadow:var(--shadow-md); z-index:150;
}
.fab:active { transform:scale(0.9); }
@media (max-width:560px) { .fab { right:16px; } }

/* Modal */
.modal-overlay {
    position:fixed; top:0; left:0; right:0; bottom:0;
    background:var(--bg-overlay); z-index:500;
    display:none; align-items:flex-end; justify-content:center;
}
.modal-overlay.active { display:flex; }
.modal {
    background:var(--bg-card); width:100%; max-width:var(--max-w);
    max-height:90vh; border-radius:16px 16px 0 0; padding:20px;
    padding-bottom:calc(20px + env(safe-area-inset-bottom,0));
    overflow-y:auto; animation:slideUpModal .25s ease;
}
@keyframes slideUpModal { from{transform:translateY(100%)} to{transform:translateY(0)} }
.modal-handle { width:36px; height:4px; background:var(--border); border-radius:2px; margin:0 auto 16px; }
.modal-title { font-size:1.05rem; font-weight:700; color:var(--text); margin-bottom:16px; }
.modal-actions { display:flex; gap:12px; margin-top:16px; }
.modal-actions .btn { flex:1; }

/* Forms */
.form-group { margin-bottom:14px; }
.form-label { display:block; font-size:0.78rem; font-weight:600; color:var(--text-secondary); margin-bottom:6px; text-transform:uppercase; letter-spacing:0.3px; }
.form-input {
    width:100%; padding:10px 14px; background:var(--bg-input);
    border:1px solid var(--border); border-radius:var(--radius-sm);
    color:var(--text); font-family:var(--font); font-size:0.9rem; outline:none;
}
.form-input:focus { border-color:var(--primary); box-shadow:0 0 0 3px var(--primary-light); }
.form-input::placeholder { color:var(--text-muted); }
textarea.form-input { resize:vertical; min-height:70px; }
select.form-input {
    appearance:none;
    background-image:url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath fill='%2394a3b8' d='M0 0l5 6 5-6z'/%3E%3C/svg%3E");
    background-repeat:no-repeat; background-position:right 12px center; padding-right:30px;
}
input[type="date"].form-input {
    appearance:none;
    -webkit-appearance:none;
    min-height: 42px;
    display: block;
}

/* Radio & Checkbox */
.radio-group, .checkbox-group { display:flex; flex-wrap:wrap; gap:8px; }
.radio-item, .checkbox-item { position:relative; }
.radio-item input, .checkbox-item input { position:absolute; opacity:0; width:0; height:0; }
.radio-item label, .checkbox-item label {
    display:flex; align-items:center; gap:6px;
    padding:8px 12px; background:var(--bg-input); border:1px solid var(--border);
    border-radius:var(--radius-sm); font-size:0.85rem; color:var(--text-secondary);
    cursor:pointer; transition:all .15s;
}
.radio-item input:checked+label, .checkbox-item input:checked+label {
    background:var(--primary-light); border-color:var(--primary); color:var(--primary);
}
.checkbox-item label { padding:9px 12px; min-width:0; }
.checkbox-item label .check-icon {
    width:16px; height:16px; border:2px solid var(--border);
    border-radius:3px; display:flex; align-items:center; justify-content:center;
    flex-shrink:0; font-size:0.65rem; color:transparent;
}
.checkbox-item input:checked+label .check-icon { background:var(--primary); border-color:var(--primary); color:#fff; }

/* Tabs */
.tabs {
    display:flex; background:var(--bg-input); border-radius:var(--radius);
    padding:3px; margin-bottom:16px; border:1px solid var(--border);
}
.tab-btn {
    flex:1; padding:9px; border:none; background:none;
    color:var(--text-muted); font-family:var(--font); font-size:0.78rem;
    font-weight:600; cursor:pointer; border-radius:var(--radius-sm);
}
.tab-btn.active { background:var(--primary); color:#fff; box-shadow:var(--shadow); }
.tab-content { display:none; }
.tab-content.active { display:block; animation:fadeIn .2s ease; }

/* Avatar */
.avatar {
    width:38px; height:38px; border-radius:50%;
    display:flex; align-items:center; justify-content:center;
    font-weight:600; font-size:0.8rem; color:#fff; flex-shrink:0;
}
.avatar.male { background:var(--primary); }
.avatar.female { background:#e879a0; }

/* Member Item */
.member-item {
    display:flex; align-items:center; gap:12px;
    padding:12px; background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); margin-bottom:8px; box-shadow:var(--shadow);
}
.member-info { flex:1; min-width:0; }
.member-name { font-weight:600; font-size:0.9rem; }
.member-gender { font-size:0.75rem; color:var(--text-muted); }
.member-item .item-actions { display:flex; gap:4px; }

/* Expense Card */
.expense-card {
    background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); padding:12px; margin-bottom:8px;
    box-shadow:var(--shadow);
}
.expense-header { display:flex; align-items:flex-start; justify-content:space-between; margin-bottom:6px; }
.expense-name { font-weight:600; font-size:0.9rem; }
.expense-amount { font-weight:700; font-size:1rem; color:var(--success); white-space:nowrap; }
.expense-details { font-size:0.78rem; color:var(--text-secondary); display:flex; flex-direction:column; gap:1px; }
.expense-details .payer { color:var(--primary); font-weight:500; }
.expense-note { font-size:0.75rem; color:var(--text-muted); font-style:italic; margin-top:3px; }
.expense-card .item-actions { display:flex; gap:4px; margin-top:8px; padding-top:8px; border-top:1px solid var(--border); }

/* Settlement */
.settlement-summary {
    background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); padding:20px; margin-bottom:16px;
    text-align:center; box-shadow:var(--shadow);
}
#settlement-content { display:block !important; }
.settlement-total { font-size:1.6rem; font-weight:700; color:var(--primary); }
.settlement-avg { font-size:0.82rem; color:var(--text-secondary); margin-top:4px; }

.balance-item {
    padding:14px; background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); margin-bottom:8px; box-shadow:var(--shadow);
}
.balance-item-header { display:flex; align-items:center; gap:10px; margin-bottom:8px; }
.balance-info { flex:1; min-width:0; }
.balance-name { font-weight:600; font-size:0.88rem; }
.balance-row { display:flex; justify-content:space-between; align-items:center; font-size:0.8rem; padding:4px 0; }
.balance-row span { color:var(--text-secondary); }
.balance-row strong { font-weight:600; }
.balance-divider { border-top:1px solid var(--border); margin:6px 0; }
.balance-result { display:flex; justify-content:space-between; align-items:center; font-size:0.88rem; padding-top:4px; }
.balance-result-label { font-weight:500; color:var(--text-secondary); }
.balance-amount { font-weight:700; font-size:0.95rem; }
.balance-amount.positive { color:var(--success); }
.balance-amount.negative { color:var(--danger); }

.transaction-item {
    padding:14px; background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); margin-bottom:8px; box-shadow:var(--shadow);
}
.transaction-header { display:flex; align-items:center; gap:10px; margin-bottom:6px; }
.transaction-icon {
    width:32px; height:32px; border-radius:50%; background:var(--primary-light);
    display:flex; align-items:center; justify-content:center;
    font-size:0.9rem; flex-shrink:0;
}
.transaction-info { flex:1; min-width:0; }
.transaction-names { font-size:0.85rem; font-weight:500; }
.transaction-names .arrow { color:var(--primary); margin:0 4px; }
.transaction-amount {
    font-weight:700; font-size:1.05rem; color:var(--primary);
    text-align:right; padding-top:4px;
}

/* Empty State */
.empty-state { text-align:center; padding:40px 16px; color:var(--text-muted); }
.empty-state .empty-icon { font-size:2.5rem; margin-bottom:12px; opacity:0.6; }
.empty-state .empty-text { font-size:0.88rem; }

/* Trip Detail */
.trip-detail-header {
    background:var(--bg-card); border:1px solid var(--border);
    border-radius:var(--radius); padding:20px; margin-bottom:16px;
    box-shadow:var(--shadow); border-left:4px solid var(--primary);
}
.trip-detail-header::before { display:none; }
.trip-detail-name { font-size:1.2rem; font-weight:700; margin-bottom:2px; }
.trip-detail-date { font-size:0.82rem; color:var(--text-secondary); }
.trip-detail-stats { display:flex; gap:20px; margin-top:14px; padding-top:14px; border-top:1px solid var(--border); }
.trip-stat { text-align:center; }
.trip-stat-value { font-size:1.05rem; font-weight:700; color:var(--primary); }
.trip-stat-label { font-size:0.68rem; color:var(--text-muted); text-transform:uppercase; letter-spacing:0.4px; }

/* Toast */
.toast {
    position:fixed; top:20px; left:50%; transform:translateX(-50%) translateY(-80px);
    background:var(--bg-card); color:var(--text); padding:12px 20px;
    border-radius:var(--radius); box-shadow:var(--shadow-md); z-index:1000;
    font-size:0.85rem; font-weight:500; border:1px solid var(--border);
    transition:transform .3s ease; max-width:calc(var(--max-w) - 32px); text-align:center;
}
.toast.show { transform:translateX(-50%) translateY(0); }
.toast.success { border-color:var(--success); background:#f0fdf4; }
.toast.error { border-color:var(--danger); background:#fef2f2; }

/* Confirm Dialog */
.confirm-overlay {
    position:fixed; top:0; left:0; right:0; bottom:0;
    background:var(--bg-overlay); z-index:600;
    display:none; align-items:center; justify-content:center; padding:20px;
}
.confirm-overlay.active { display:flex; }
.confirm-dialog {
    background:var(--bg-card); border-radius:var(--radius); padding:24px;
    max-width:320px; width:100%; text-align:center; animation:slideUp .2s ease;
    box-shadow:var(--shadow-md);
}
.confirm-dialog .confirm-icon { font-size:2.2rem; margin-bottom:12px; }
.confirm-dialog .confirm-title { font-size:1rem; font-weight:700; margin-bottom:6px; }
.confirm-dialog .confirm-message { font-size:0.85rem; color:var(--text-secondary); margin-bottom:16px; }
.confirm-dialog .confirm-actions { display:flex; gap:10px; }
.confirm-dialog .confirm-actions .btn { flex:1; }

/* Loading */
.loading { display:flex; align-items:center; justify-content:center; padding:40px; }
.loading::after {
    content:''; width:28px; height:28px;
    border:3px solid var(--border); border-top-color:var(--primary);
    border-radius:50%; animation:spin .7s linear infinite;
}
@keyframes spin { to{transform:rotate(360deg)} }

/* Animate */
.animate-in { animation:slideUp .25s ease forwards; }
.animate-in:nth-child(2){animation-delay:.04s}
.animate-in:nth-child(3){animation-delay:.08s}
.animate-in:nth-child(4){animation-delay:.12s}
.animate-in:nth-child(5){animation-delay:.16s}

/* Trip amount */
.trip-amount { font-size:0.85rem; font-weight:600; color:var(--success); margin-top:6px; }

/* Add member btn */
.add-member-btn {
    width:100%; padding:12px; background:var(--primary-light);
    border:1px dashed var(--primary); border-radius:var(--radius);
    color:var(--primary); font-family:var(--font); font-size:0.85rem;
    font-weight:600; cursor:pointer; display:flex; align-items:center;
    justify-content:center; gap:6px;
}
.add-member-btn:active { background:var(--primary); color:#fff; }

/* Checkbox list */
.checkbox-list {
    display:flex; flex-direction:column; gap:6px;
    max-height:200px; overflow-y:auto; padding:8px;
    background:var(--bg-input); border-radius:var(--radius-sm); border:1px solid var(--border);
}
.checkbox-list .checkbox-item label { width:100%; }

/* Select all */
.select-all-row { display:flex; justify-content:flex-end; margin-bottom:4px; }
.select-all-btn {
    background:none; border:none; color:var(--primary);
    font-family:var(--font); font-size:0.75rem; font-weight:600; cursor:pointer; padding:4px 6px;
}

/* Responsive */
@media (min-width:561px) { #app { box-shadow:var(--shadow); } }

/* Scrollbar */
::-webkit-scrollbar { width:4px; }
::-webkit-scrollbar-thumb { background:var(--border); border-radius:2px; }

/* Login Page Styles */
.login-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    min-height: 80vh;
    text-align: center;
    padding: 20px;
}
.login-logo {
    font-size: 4rem;
    margin-bottom: 20px;
}
.login-container h2 {
    font-size: 1.5rem;
    color: var(--primary);
    margin-bottom: 8px;
}
.login-container p {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 30px;
    max-width: 300px;
}
.auth-buttons {
    display: flex;
    flex-direction: column;
    gap: 16px;
    width: 100%;
    max-width: 280px;
    align-items: center;
}
.apple-login-btn {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 10px;
    width: 100%;
    padding: 10px 16px;
    background-color: #000;
    color: #fff;
    border: none;
    border-radius: 4px;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    font-size: 15px;
    font-weight: 500;
    cursor: pointer;
    box-shadow: 0 2px 4px rgba(0,0,0,0.2);
}
.apple-login-btn:hover {
    background-color: #333;
}
.header-action-btn {
    background: none;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    padding: 4px;
    display: flex;
    margin-left: auto;
}
.header-action-btn:hover {
    color: var(--danger);
}