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

:root {
    --bg: #C8F0EE;
    --surface: #ffffff;
    --border: #e0e0e0;
    --text: #1a1a1a;
    --text-muted: #888;
    --accent: #2563eb;
    --accent-hover: #1d4ed8;
    --done-text: #aaa;
    --danger: #dc2626;
    --radius: 8px;
    --shadow: 0 1px 3px rgba(0,0,0,.08);
}

body {
    font-family: system-ui, -apple-system, sans-serif;
    font-size: 15px;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
}

.app {
    max-width: 680px;
    margin: 0 auto;
    padding: 32px 16px 64px;
}

header {
    margin-bottom: 28px;
}

h1 {
    font-size: 22px;
    font-weight: 700;
    letter-spacing: -.3px;
    color: var(--text);
}

/* Tabs */
.tabs {
    display: flex;
    gap: 4px;
    border-bottom: 2px solid var(--border);
    margin-bottom: 28px;
    flex-wrap: wrap;
}

.tab {
    padding: 8px 18px;
    font-size: 14px;
    font-weight: 500;
    background: none;
    border: none;
    border-bottom: 2px solid transparent;
    margin-bottom: -2px;
    cursor: pointer;
    color: var(--text-muted);
    border-radius: var(--radius) var(--radius) 0 0;
    transition: color .15s, border-color .15s;
    text-transform: uppercase;
    letter-spacing: .5px;
}

.tab:hover {
    color: var(--text);
}

.tab.active {
    color: var(--accent);
    border-bottom-color: var(--accent);
}

/* Task header */
.task-header {
    display: flex;
    align-items: baseline;
    gap: 10px;
    margin-bottom: 16px;
}

.project-title {
    font-size: 18px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: .5px;
}

.task-count {
    font-size: 13px;
    color: var(--text-muted);
}

/* Task list */
.task-list {
    list-style: none;
    display: flex;
    flex-direction: column;
    gap: 2px;
    margin-bottom: 20px;
    min-height: 40px;
}

.task-item {
    display: flex;
    align-items: center;
    gap: 12px;
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 11px 14px;
    transition: opacity .15s;
}

.task-item.done {
    opacity: .7;
}

.task-item input[type="checkbox"] {
    width: 17px;
    height: 17px;
    cursor: pointer;
    accent-color: var(--accent);
    flex-shrink: 0;
}

.task-text {
    flex: 1;
    font-size: 14px;
    line-height: 1.4;
    transition: color .15s, text-decoration .15s;
}

.task-item.done .task-text {
    text-decoration: line-through;
    color: var(--done-text);
}

.delete-btn {
    background: none;
    border: none;
    cursor: pointer;
    color: var(--text-muted);
    font-size: 17px;
    line-height: 1;
    padding: 0 2px;
    opacity: 0;
    transition: opacity .15s, color .15s;
}

.task-item:hover .delete-btn {
    opacity: 1;
}

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

/* Empty state */
.empty {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 0;
    color: var(--text-muted);
    font-size: 14px;
}

/* Add form */
.add-form {
    display: flex;
    gap: 8px;
}

.add-form input {
    flex: 1;
    padding: 10px 14px;
    font-size: 14px;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    outline: none;
    background: var(--surface);
    color: var(--text);
    transition: border-color .15s, box-shadow .15s;
}

.add-form input:focus {
    border-color: var(--accent);
    box-shadow: 0 0 0 3px rgba(37,99,235,.12);
}

.add-form button {
    padding: 10px 20px;
    font-size: 14px;
    font-weight: 600;
    background: var(--accent);
    color: #fff;
    border: none;
    border-radius: var(--radius);
    cursor: pointer;
    transition: background .15s;
}

.add-form button:hover {
    background: var(--accent-hover);
}

/* Loading indicator */
.loading {
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 40px 0;
    color: var(--text-muted);
    font-size: 14px;
}