/* ============ Reset & Base ============ */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

:root {
    --bg-gradient: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    --card-bg: #ffffff;
    --bg-soft: #f5f7fb;
    --text-primary: #1a1d29;
    --text-secondary: #6b7280;
    --text-muted: #9ca3af;
    --border: #e5e7eb;
    --border-focus: #667eea;

    --income: #10b981;
    --income-bg: #d1fae5;
    --expense: #ef4444;
    --expense-bg: #fee2e2;
    --balance: #1a1d29;

    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 10px 30px rgba(0, 0, 0, 0.12);

    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Oxygen,
        Ubuntu, sans-serif;
    background: var(--bg-gradient);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.5;
    padding: 20px;
    -webkit-font-smoothing: antialiased;
}

/* ============ Layout ============ */
.app {
    max-width: 520px;
    margin: 0 auto;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* ============ Header ============ */
.header {
    text-align: center;
    color: #fff;
    padding: 10px 0;
}

.header h1 {
    font-size: 1.9rem;
    font-weight: 700;
    letter-spacing: -0.5px;
    margin-bottom: 4px;
}

.subtitle {
    font-size: 0.95rem;
    opacity: 0.85;
}

/* ============ Cards ============ */
.balance-card,
.form-section,
.history-section,
.summary-card {
    background: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.balance-card {
    padding: 24px;
    text-align: center;
    background: linear-gradient(135deg, #ffffff 0%, #f9fafb 100%);
}

.balance-card h2 {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 8px;
}

.balance-amount {
    font-size: 2.5rem;
    font-weight: 700;
    color: var(--balance);
    letter-spacing: -1px;
    word-break: break-all;
}

.balance-amount.positive {
    color: var(--income);
}

.balance-amount.negative {
    color: var(--expense);
}

.status-badge {
    display: inline-block;
    margin-top: 10px;
    padding: 4px 12px;
    background: var(--bg-soft);
    border-radius: 999px;
    font-size: 0.8rem;
    color: var(--text-secondary);
    font-weight: 500;
}

/* ============ Summary Cards ============ */
.summary {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 14px;
}

.summary-card {
    padding: 18px;
    position: relative;
    overflow: hidden;
    transition: transform 0.2s, box-shadow 0.2s;
}

.summary-card:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
}

.summary-card.income {
    border-top: 3px solid var(--income);
}

.summary-card.expense {
    border-top: 3px solid var(--expense);
}

.summary-label {
    font-size: 0.8rem;
    color: var(--text-secondary);
    text-transform: uppercase;
    letter-spacing: 0.5px;
    font-weight: 600;
}

.summary-icon {
    position: absolute;
    top: 16px;
    right: 18px;
    font-size: 1.4rem;
    font-weight: 700;
    width: 30px;
    height: 30px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.income .summary-icon {
    background: var(--income-bg);
    color: var(--income);
}

.expense .summary-icon {
    background: var(--expense-bg);
    color: var(--expense);
}

.summary-amount {
    font-size: 1.5rem;
    font-weight: 700;
    margin-top: 6px;
    letter-spacing: -0.5px;
}

.income .summary-amount {
    color: var(--income);
}

.expense .summary-amount {
    color: var(--expense);
}

/* ============ Form Section ============ */
.form-section,
.history-section {
    padding: 22px;
}

.form-section h3,
.history-section h3 {
    font-size: 1.05rem;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.form-group {
    margin-bottom: 14px;
}

.form-group label {
    display: block;
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 6px;
}

input[type="text"],
input[type="number"],
select {
    width: 100%;
    padding: 11px 14px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-family: inherit;
    color: var(--text-primary);
    background: #fff;
    transition: border-color 0.2s, box-shadow 0.2s;
}

input[type="text"]:focus,
input[type="number"]:focus,
select:focus {
    outline: none;
    border-color: var(--border-focus);
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.15);
}

/* Type toggle */
.type-toggle {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
}

.type-toggle input {
    display: none;
}

.type-option {
    text-align: center;
    padding: 10px;
    border: 1.5px solid var(--border);
    border-radius: var(--radius-sm);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
    user-select: none;
}

#type-income:checked ~ .income-option,
#type-expense:checked ~ .expense-option {
    color: #fff;
    border-color: transparent;
}

#type-income:checked ~ .income-option {
    background: var(--income);
}

#type-expense:checked ~ .expense-option {
    background: var(--expense);
}

.income-option:hover,
.expense-option:hover {
    background: var(--bg-soft);
}

#type-income:checked ~ .income-option:hover,
#type-expense:checked ~ .expense-option:hover {
    filter: brightness(0.95);
}

/* Submit button */
.btn-submit {
    width: 100%;
    padding: 13px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: #fff;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 6px;
    transition: transform 0.15s, box-shadow 0.2s;
    font-family: inherit;
}

.btn-submit:hover {
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

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

/* ============ History Section ============ */
.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 10px;
    margin-bottom: 14px;
}

.history-header h3 {
    margin-bottom: 0;
}

.filter-buttons {
    display: flex;
    gap: 6px;
    background: var(--bg-soft);
    padding: 4px;
    border-radius: 999px;
}

.filter-btn {
    border: none;
    background: transparent;
    padding: 6px 14px;
    border-radius: 999px;
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all 0.2s;
    font-family: inherit;
}

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

.filter-btn.active {
    background: #fff;
    color: var(--text-primary);
    box-shadow: var(--shadow-sm);
}

/* Transaction list */
.transaction-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 8px;
}

.transaction-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 14px;
    background: var(--bg-soft);
    border-radius: var(--radius-sm);
    border-left: 3px solid transparent;
    transition: transform 0.15s, background 0.2s;
    animation: slideIn 0.3s ease-out;
}

.transaction-item:hover {
    background: #eef0f6;
    transform: translateX(2px);
}

.transaction-item.income {
    border-left-color: var(--income);
}

.transaction-item.expense {
    border-left-color: var(--expense);
}

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

.transaction-icon {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    flex-shrink: 0;
}

.transaction-item.income .transaction-icon {
    background: var(--income-bg);
    color: var(--income);
}

.transaction-item.expense .transaction-icon {
    background: var(--expense-bg);
    color: var(--expense);
}

.transaction-details {
    flex: 1;
    min-width: 0;
}

.transaction-description {
    font-weight: 600;
    color: var(--text-primary);
    font-size: 0.95rem;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.transaction-meta {
    font-size: 0.78rem;
    color: var(--text-muted);
    display: flex;
    gap: 8px;
    margin-top: 2px;
}

.transaction-category {
    background: #fff;
    padding: 1px 8px;
    border-radius: 999px;
    font-weight: 500;
}

.transaction-amount {
    font-weight: 700;
    font-size: 1rem;
    flex-shrink: 0;
}

.transaction-item.income .transaction-amount {
    color: var(--income);
}

.transaction-item.expense .transaction-amount {
    color: var(--expense);
}

.delete-btn {
    background: transparent;
    border: none;
    color: var(--text-muted);
    cursor: pointer;
    font-size: 1.1rem;
    padding: 4px 8px;
    border-radius: 6px;
    transition: all 0.2s;
    flex-shrink: 0;
}

.delete-btn:hover {
    color: var(--expense);
    background: var(--expense-bg);
}

/* Empty state */
.empty-state {
    text-align: center;
    padding: 30px 20px;
    color: var(--text-muted);
}

.empty-state.hidden {
    display: none;
}

.empty-icon {
    font-size: 3rem;
    margin-bottom: 8px;
    opacity: 0.5;
}

.empty-state p {
    font-size: 1.05rem;
    font-weight: 600;
    color: var(--text-secondary);
    margin-bottom: 4px;
}

.empty-state span {
    font-size: 0.88rem;
}

/* ============ Footer ============ */
.footer {
    text-align: center;
    padding: 10px 0 20px;
}

.btn-clear {
    background: transparent;
    border: 1.5px solid rgba(255, 255, 255, 0.4);
    color: #fff;
    padding: 8px 18px;
    border-radius: 999px;
    font-size: 0.85rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.2s;
    font-family: inherit;
}

.btn-clear:hover {
    background: rgba(255, 255, 255, 0.15);
    border-color: rgba(255, 255, 255, 0.7);
}

/* ============ Responsive ============ */
@media (max-width: 480px) {
    body {
        padding: 14px;
    }

    .header h1 {
        font-size: 1.6rem;
    }

    .balance-amount {
        font-size: 2rem;
    }

    .summary-amount {
        font-size: 1.25rem;
    }

    .form-section,
    .history-section {
        padding: 18px;
    }
}