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

:root {
    --bg: #ffffff;
    --fg: #000000;
    --border: #e5e5e5;
    --muted: #737373;
    --muted-bg: #f5f5f5;
    --radius: 8px;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, sans-serif;
    background: var(--bg);
    color: var(--fg);
    line-height: 1.5;
    -webkit-font-smoothing: antialiased;
}

.container {
    max-width: 640px;
    margin: 0 auto;
    padding: 20px;
    min-height: 100vh;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 32px;
    padding-bottom: 16px;
    border-bottom: 1px solid var(--border);
}

h1 {
    font-size: 24px;
    font-weight: 600;
}

h2 {
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 16px;
}

.header-actions {
    display: flex;
    gap: 8px;
}

button {
    font-family: inherit;
    font-size: 14px;
    font-weight: 500;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: all 0.15s;
}

.btn-primary {
    background: var(--fg);
    color: var(--bg);
    padding: 8px 16px;
}

.btn-primary:hover {
    opacity: 0.9;
}

.btn-secondary {
    background: var(--muted-bg);
    color: var(--fg);
    padding: 8px 16px;
}

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

.btn-ghost {
    background: transparent;
    color: var(--fg);
    padding: 8px 16px;
}

.btn-ghost:hover {
    background: var(--muted-bg);
}

.btn-icon {
    background: transparent;
    padding: 8px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: 1px solid var(--border);
}

.btn-icon:hover {
    background: var(--muted-bg);
}

.btn-icon-small {
    background: transparent;
    padding: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    border: none;
}

.btn-icon-small:hover {
    background: var(--muted-bg);
    border-radius: 4px;
}

.icon {
    width: 20px;
    height: 20px;
}

.icon-small {
    width: 16px;
    height: 16px;
}

.inline-icon {
    width: 16px;
    height: 16px;
    vertical-align: text-bottom;
    margin-right: 4px;
}

.full-width {
    width: 100%;
    padding: 12px;
}

.hidden {
    display: none !important;
}

.period-selector {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
}

.period-btn {
    flex: 1;
    padding: 8px 16px;
    background: transparent;
    border: 1px solid var(--border);
    color: var(--fg);
    font-size: 14px;
}

.period-btn.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.stats-grid {
    display: grid;
    grid-template-columns: repeat(2, 1fr);
    gap: 12px;
    margin-bottom: 32px;
}

.stat-card {
    padding: 20px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
}

.stat-value {
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 4px;
}

.stat-label {
    font-size: 13px;
    color: var(--muted);
}

.sessions-container {
    margin-top: 32px;
}

.session-item {
    padding: 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 12px;
}

.session-header-info {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 8px;
}

.session-date {
    font-weight: 600;
    font-size: 15px;
}

.session-duration {
    font-size: 14px;
    color: var(--muted);
}

.session-rating {
    display: inline-block;
    padding: 4px 10px;
    background: var(--muted-bg);
    border-radius: 4px;
    font-size: 13px;
    margin-bottom: 8px;
}

.session-notes {
    font-size: 14px;
    color: var(--muted);
    margin-bottom: 8px;
}

.session-pieces {
    font-size: 13px;
    color: var(--muted);
}

.session-actions {
    margin-top: 12px;
    display: flex;
    gap: 8px;
}

.session-view {
    padding-top: 16px;
}

.session-header {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 24px;
}

.timer-section {
    padding: 24px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 24px;
}

.timer-mode {
    display: flex;
    gap: 8px;
    margin-bottom: 20px;
}

.mode-btn {
    flex: 1;
    padding: 8px;
    background: transparent;
    border: 1px solid var(--border);
    font-size: 14px;
}

.mode-btn.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.timer-goals {
    display: flex;
    gap: 8px;
    margin-bottom: 24px;
}

.goal-btn {
    flex: 1;
    padding: 10px;
    background: var(--muted-bg);
    border: 1px solid var(--border);
    font-size: 14px;
}

.goal-btn.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.timer-display {
    font-size: 64px;
    font-weight: 700;
    text-align: center;
    margin: 32px 0;
    font-variant-numeric: tabular-nums;
}

.timer-controls {
    display: flex;
    gap: 8px;
}

.timer-controls button {
    flex: 1;
}

.form-group {
    margin-bottom: 24px;
}

label {
    display: block;
    font-size: 14px;
    font-weight: 500;
    margin-bottom: 8px;
}

textarea,
input[type="text"] {
    width: 100%;
    padding: 10px;
    font-family: inherit;
    font-size: 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    background: var(--bg);
    color: var(--fg);
    resize: vertical;
}

textarea:focus,
input[type="text"]:focus {
    outline: none;
    border-color: var(--fg);
}

.rating-selector {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.rating-btn {
    padding: 8px 16px;
    background: var(--muted-bg);
    border: 1px solid var(--border);
    font-size: 13px;
}

.rating-btn.active {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.pieces-selector {
    display: flex;
    gap: 8px;
    margin-bottom: 12px;
}

.pieces-selector input {
    flex: 1;
}

.existing-pieces {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-bottom: 12px;
}

.piece-btn {
    padding: 6px 12px;
    background: var(--muted-bg);
    border: 1px solid var(--border);
    font-size: 13px;
}

.piece-btn.selected {
    background: var(--fg);
    color: var(--bg);
    border-color: var(--fg);
}

.selected-pieces {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 12px;
}

.selected-piece {
    padding: 6px 12px;
    background: var(--fg);
    color: var(--bg);
    border-radius: 4px;
    font-size: 13px;
    display: flex;
    align-items: center;
    gap: 8px;
}

.piece-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    margin-bottom: 12px;
}

.piece-name {
    display: flex;
    align-items: center;
    font-size: 15px;
    font-weight: 500;
}

.remove-piece {
    background: none;
    border: none;
    color: var(--bg);
    cursor: pointer;
    padding: 0;
    font-size: 16px;
    line-height: 1;
}

.overlay {
    position: fixed;
    inset: 0;
    background: rgba(0, 0, 0, 0.8);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    animation: fadeIn 0.3s;
}

.completion-content {
    text-align: center;
    animation: scaleIn 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.completion-icon {
    font-size: 80px;
    margin-bottom: 16px;
}

.completion-text {
    font-size: 32px;
    font-weight: 700;
    color: white;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes scaleIn {
    from {
        transform: scale(0.5);
        opacity: 0;
    }
    to {
        transform: scale(1);
        opacity: 1;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 16px;
    }

    h1 {
        font-size: 20px;
    }

    .timer-display {
        font-size: 48px;
    }

    .stats-grid {
        gap: 8px;
    }

    .stat-card {
        padding: 16px;
    }

    .stat-value {
        font-size: 24px;
    }
}