/* ===== Design tokens ===== */
:root {
    --color-bg: #f4f6f8;
    --color-surface: #ffffff;
    --color-border: #e2e6ea;
    --color-text: #1f2937;
    --color-text-muted: #6b7280;
    --color-primary: #2563eb;
    --color-primary-hover: #1d4ed8;
    --color-danger: #dc2626;
    --color-danger-hover: #b91c1c;
    --color-positive: #16a34a;
    --color-negative: #dc2626;

    --radius: 10px;
    --shadow: 0 1px 3px rgba(0, 0, 0, 0.08), 0 1px 2px rgba(0, 0, 0, 0.04);
    --spacing: 1rem;
}

/* ===== Reset ===== */
* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--color-bg);
    color: var(--color-text);
    line-height: 1.5;
}

h1, h2 {
    margin: 0 0 0.5rem 0;
}

ul {
    list-style: none;
    margin: 0;
    padding: 0;
}

/* ===== Header ===== */
.app-header {
    text-align: center;
    padding: 2rem 1rem 1.5rem;
}

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

.app-header .subtitle {
    margin: 0;
    color: var(--color-text-muted);
}

/* ===== Layout ===== */
.app-main {
    max-width: 720px;
    margin: 0 auto;
    padding: 0 1rem 2rem;
    display: flex;
    flex-direction: column;
    gap: 1.25rem;
}

.app-footer {
    text-align: center;
    color: var(--color-text-muted);
    font-size: 0.85rem;
    padding: 1rem;
}

/* ===== Card ===== */
.card {
    background-color: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 1.25rem;
}

.card h2 {
    font-size: 1.15rem;
}

.card-danger {
    border-color: #fca5a5;
}

/* ===== Forms ===== */
.inline-form {
    display: flex;
    gap: 0.75rem;
    align-items: flex-end;
    flex-wrap: wrap;
}

.form-field {
    display: flex;
    flex-direction: column;
    gap: 0.35rem;
    margin-bottom: 0.85rem;
    flex: 1 1 200px;
}

.form-field label,
.field-label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--color-text-muted);
}

input[type="text"],
input[type="number"],
select {
    padding: 0.6rem 0.75rem;
    border: 1px solid var(--color-border);
    border-radius: 8px;
    font-size: 1rem;
    background-color: var(--color-surface);
    color: var(--color-text);
    width: 100%;
}

input:focus,
select:focus,
button:focus-visible {
    outline: 2px solid var(--color-primary);
    outline-offset: 1px;
}

.split-type-value {
    margin: 0;
    padding: 0.6rem 0.75rem;
    background-color: var(--color-bg);
    border-radius: 8px;
    font-size: 0.95rem;
}

.checkbox-list {
    display: flex;
    flex-direction: column;
    gap: 0.4rem;
}

.checkbox-list li {
    display: flex;
}

.checkbox-item-label {
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-weight: 400;
    color: var(--color-text);
    cursor: pointer;
}

.form-message {
    min-height: 1.1rem;
    color: var(--color-danger);
    font-size: 0.85rem;
    margin: 0.25rem 0 0.5rem;
}

.hint-message {
    color: var(--color-text-muted);
    font-size: 0.85rem;
    margin: 0.75rem 0 0;
}

.hint-message[hidden] {
    display: none;
}

fieldset {
    border: none;
    margin: 0;
    padding: 0;
}

fieldset:disabled {
    opacity: 0.55;
}

fieldset:disabled input,
fieldset:disabled select,
fieldset:disabled button {
    cursor: not-allowed;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* ===== Buttons ===== */
.btn {
    border: none;
    border-radius: 8px;
    padding: 0.65rem 1.1rem;
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    min-height: 44px;
    transition: background-color 0.15s ease, border-color 0.15s ease;
}

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

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

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

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

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

.btn-secondary:hover {
    background-color: var(--color-bg);
    border-color: #c7ccd3;
}

.btn-small {
    padding: 0.35rem 0.7rem;
    font-size: 0.85rem;
    min-height: 36px;
}

/* ===== Lists ===== */
.member-list,
.expense-list,
.balance-list,
.settlement-list {
    display: flex;
    flex-direction: column;
    gap: 0.6rem;
    margin-top: 0.75rem;
}

.member-list li,
.expense-list li,
.balance-list li,
.settlement-list li {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.65rem 0.85rem;
    background-color: var(--color-bg);
    border-radius: 8px;
}

.expense-list li {
    align-items: flex-start;
    gap: 0.75rem;
}

.expense-item-info {
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
}

.expense-item-description {
    font-weight: 700;
    margin: 0;
}

.expense-item-amount {
    margin: 0;
    color: var(--color-primary);
    font-weight: 600;
}

.expense-item-meta {
    margin: 0;
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.btn-delete-expense {
    flex-shrink: 0;
}

.empty-state {
    color: var(--color-text-muted);
    font-style: italic;
    justify-content: center !important;
    background-color: transparent !important;
}

/* ===== Summary ===== */
.summary-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.75rem;
    margin-top: 0.75rem;
}

.summary-item {
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
    padding: 0.75rem;
    background-color: var(--color-bg);
    border-radius: 8px;
    text-align: center;
}

.summary-label {
    font-size: 0.8rem;
    color: var(--color-text-muted);
}

.summary-value {
    font-size: 1.15rem;
    font-weight: 700;
}

/* ===== Balance indicators ===== */
.balance-list li {
    align-items: flex-start;
    gap: 0.75rem;
}

.balance-item-info {
    display: flex;
    flex-direction: column;
    gap: 0.15rem;
}

.balance-item-name {
    font-weight: 700;
    margin: 0;
}

.balance-item-meta {
    margin: 0;
    font-size: 0.85rem;
    color: var(--color-text-muted);
}

.balance-item-amount-wrap {
    display: flex;
    flex-direction: column;
    align-items: flex-end;
    flex-shrink: 0;
}

.balance-item-amount {
    margin: 0;
    font-size: 1.05rem;
}

.balance-item-status {
    margin: 0;
    font-size: 0.75rem;
    color: var(--color-text-muted);
}

.balance-positive {
    color: var(--color-positive);
    font-weight: 700;
}

.balance-negative {
    color: var(--color-negative);
    font-weight: 700;
}

/* ===== Settlement ===== */
.settlement-item-label {
    margin: 0;
    font-weight: 600;
}

.settlement-item-amount {
    margin: 0;
    font-weight: 700;
    color: var(--color-primary);
}

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

    .inline-form {
        flex-direction: column;
        align-items: stretch;
    }

    .btn {
        width: 100%;
    }

    .expense-list li,
    .balance-list li {
        flex-direction: column;
        align-items: stretch;
    }

    .balance-item-amount-wrap {
        align-items: flex-start;
    }

    .settlement-list li {
        flex-wrap: wrap;
        row-gap: 0.25rem;
    }
}

/* ===== Two-column desktop layout =====
   Expense List sits in its own right-hand column; every other section
   stacks in the left-hand column, in the same order as the markup. */
@media (min-width: 900px) {
    .app-main {
        max-width: 1100px;
        display: grid;
        grid-template-columns: 1fr 1fr;
        align-items: start;
        grid-template-areas:
            "members     expenses"
            "add-expense expenses"
            "summary     expenses"
            "balance     expenses"
            "settlement  expenses"
            "clear       expenses";
    }

    #members-section { grid-area: members; }
    #add-expense-section { grid-area: add-expense; }
    #expense-list-section { grid-area: expenses; }
    #summary-section { grid-area: summary; }
    #balance-section { grid-area: balance; }
    #settlement-section { grid-area: settlement; }
    #clear-data-section { grid-area: clear; }
}