:root {
    --teal: #0F766E;
    --teal-dark: #0D6560;
    --teal-light: #CCFBF1;
    --teal-bg: #F0FDFA;
    --orange: #F97316;
    --orange-dark: #EA6A0E;
    --orange-light: #FFF7ED;
    --dark: #1E293B;
    --grey: #64748B;
    --grey-light: #94A3B8;
    --border: #E2E8F0;
    --bg: #F8FAFC;
    --white: #FFFFFF;
    --red: #EF4444;
    --green: #22C55E;
    --shadow-sm: 0 1px 2px rgba(0,0,0,0.05);
    --shadow: 0 1px 3px rgba(0,0,0,0.08), 0 1px 2px rgba(0,0,0,0.04);
    --shadow-md: 0 4px 6px rgba(0,0,0,0.06), 0 2px 4px rgba(0,0,0,0.04);
    --radius: 10px;
    --radius-sm: 6px;
}

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

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    background: var(--bg);
    color: var(--dark);
    line-height: 1.6;
    min-height: 100vh;
}

/* ── Layout ── */
.container {
    max-width: 880px;
    margin: 0 auto;
    padding: 16px 20px;
}

/* ── Header ── */
header {
    padding: 20px 0 16px;
}

.header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

header h1 {
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--teal);
    letter-spacing: -0.3px;
}

.btn-logout {
    padding: 6px 14px;
    background: var(--white);
    border: 1px solid var(--border);
    border-radius: 20px;
    cursor: pointer;
    color: var(--grey);
    font-size: 0.78rem;
    font-weight: 500;
    transition: all 0.2s;
}

.btn-logout:hover {
    border-color: var(--red);
    color: var(--red);
    background: #FEF2F2;
}

/* ── Tabs ── */
.tabs {
    display: flex;
    gap: 4px;
    margin-bottom: 20px;
    background: var(--white);
    border-radius: var(--radius);
    padding: 4px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
}

.tab-btn {
    flex: 1;
    padding: 9px 16px;
    border: none;
    background: none;
    font-size: 0.82rem;
    font-weight: 500;
    cursor: pointer;
    color: var(--grey);
    border-radius: 7px;
    transition: all 0.2s;
}

.tab-btn:hover {
    color: var(--dark);
    background: var(--bg);
}

.tab-btn.active {
    color: var(--white);
    background: var(--teal);
    font-weight: 600;
    box-shadow: 0 1px 3px rgba(15, 118, 110, 0.3);
}

.tab-content {
    display: none;
    animation: fadeUp 0.25s ease-out;
}

.tab-content.active {
    display: block;
}

@keyframes fadeUp {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ── Card ── */
.card {
    background: var(--white);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow);
    border: 1px solid var(--border);
}

/* ── Form ── */
.form-row {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
    margin-bottom: 14px;
}

.form-group {
    display: flex;
    flex-direction: column;
}

.form-group label {
    font-size: 0.78rem;
    font-weight: 600;
    margin-bottom: 5px;
    color: var(--grey);
    text-transform: uppercase;
    letter-spacing: 0.3px;
}

.form-group input,
.form-group select {
    padding: 9px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.88rem;
    transition: all 0.2s;
    background: var(--white);
    color: var(--dark);
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--teal);
    box-shadow: 0 0 0 3px rgba(15, 118, 110, 0.1);
}

/* ── Section headings ── */
h3 {
    margin: 18px 0 10px;
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--grey);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

/* ── Line Items ── */
.item-row {
    display: grid;
    grid-template-columns: 3fr 1fr 1fr auto;
    gap: 8px;
    margin-bottom: 8px;
    align-items: end;
}

.item-row input {
    padding: 9px 12px;
    border: 1px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.88rem;
    transition: all 0.2s;
}

.item-row input:focus {
    outline: none;
    border-color: var(--teal);
    box-shadow: 0 0 0 3px rgba(15, 118, 110, 0.1);
}

.btn-remove {
    padding: 9px 12px;
    background: #FEF2F2;
    color: var(--red);
    border: 1px solid #FECACA;
    border-radius: var(--radius-sm);
    cursor: pointer;
    font-size: 0.9rem;
    transition: all 0.2s;
}

.btn-remove:hover {
    background: var(--red);
    color: var(--white);
    border-color: var(--red);
}

.btn-add {
    padding: 7px 14px;
    background: var(--teal-bg);
    border: 1px dashed var(--teal);
    border-radius: var(--radius-sm);
    cursor: pointer;
    color: var(--teal);
    margin-top: 4px;
    font-size: 0.82rem;
    font-weight: 500;
    transition: all 0.2s;
}

.btn-add:hover {
    background: var(--teal-light);
}

/* ── Submit Button ── */
.btn-submit {
    width: 100%;
    padding: 12px;
    background: linear-gradient(135deg, var(--teal), var(--teal-dark));
    color: var(--white);
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 20px;
    transition: all 0.2s;
    box-shadow: 0 2px 8px rgba(15, 118, 110, 0.25);
}

.btn-submit:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(15, 118, 110, 0.35);
}

.btn-submit:active {
    transform: translateY(0);
}

.btn-submit:disabled {
    background: var(--grey-light);
    cursor: not-allowed;
    box-shadow: none;
    transform: none;
}

/* ── Invoice List ── */
.invoice-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.invoice-card {
    background: var(--white);
    border-radius: var(--radius);
    padding: 14px 18px;
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--border);
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.2s;
}

.invoice-card:hover {
    box-shadow: var(--shadow-md);
    border-color: #CBD5E1;
}

.invoice-info h4 {
    font-size: 0.9rem;
    font-weight: 600;
    margin-bottom: 2px;
    color: var(--dark);
}

.invoice-info span {
    font-size: 0.8rem;
    color: var(--grey-light);
}

.invoice-actions {
    display: flex;
    gap: 6px;
    align-items: center;
}

.badge {
    padding: 3px 10px;
    border-radius: 20px;
    font-size: 0.7rem;
    font-weight: 600;
    text-transform: uppercase;
    cursor: pointer;
    border: none;
    letter-spacing: 0.3px;
    transition: all 0.2s;
}

.badge-unpaid {
    background: var(--orange-light);
    color: var(--orange);
}

.badge-unpaid:hover {
    background: #FFEDD5;
}

.badge-paid {
    background: #F0FDF4;
    color: var(--green);
}

.badge-paid:hover {
    background: #DCFCE7;
}

.btn-pdf {
    padding: 5px 12px;
    background: var(--orange);
    color: var(--white);
    border: none;
    border-radius: 20px;
    cursor: pointer;
    font-size: 0.78rem;
    font-weight: 600;
    transition: all 0.2s;
}

.btn-pdf:hover {
    background: var(--orange-dark);
    transform: translateY(-1px);
    box-shadow: 0 2px 8px rgba(249, 115, 22, 0.3);
}

.empty-state {
    text-align: center;
    padding: 50px 20px;
    color: var(--grey-light);
    font-size: 0.9rem;
}

/* ── Toast ── */
.toast {
    position: fixed;
    bottom: 24px;
    right: 24px;
    background: var(--dark);
    color: var(--white);
    padding: 12px 20px;
    border-radius: var(--radius);
    font-size: 0.85rem;
    font-weight: 500;
    opacity: 0;
    transform: translateY(10px);
    transition: all 0.3s;
    z-index: 1000;
    box-shadow: var(--shadow-md);
}

.toast.show {
    opacity: 1;
    transform: translateY(0);
}

/* ── App Footer ── */
.app-footer {
    text-align: center;
    padding: 24px 20px 16px;
    margin-top: 32px;
    border-top: 1px solid var(--border);
}

.app-footer p {
    font-size: 0.75rem;
    color: var(--grey-light);
    letter-spacing: 0.2px;
}

.app-footer strong {
    color: var(--grey);
    font-weight: 600;
}

/* ── Responsive ── */
@media (max-width: 600px) {
    .form-row {
        grid-template-columns: 1fr;
    }

    .item-row {
        grid-template-columns: 1fr;
    }

    .invoice-card {
        flex-direction: column;
        align-items: flex-start;
        gap: 10px;
    }

    .tabs {
        flex-wrap: wrap;
    }

    .tab-btn {
        font-size: 0.78rem;
        padding: 8px 12px;
    }
}