:root {
    --primary-color: #6c5ce7;
    --success-color: #00b894;
    --danger-color: #d63031;
    --bg-card: #ffffff;
    --shadow: 0 8px 30px rgba(0, 0, 0, 0.12);
}

body {
    background: linear-gradient(135deg, #fdfbfb 0%, #ebedee 100%);
}

.activity-header {
    text-align: center;
    margin-bottom: 3rem;
}

.activity-header h1 {
    font-size: 2.5rem;
    color: #2d3436;
    margin-bottom: 0.5rem;
}

.btn-primary {
    background: var(--primary-color);
    color: white;
    border: none;
    padding: 0.8rem 1.5rem;
    border-radius: 50px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.2s, box-shadow 0.2s;
    box-shadow: 0 4px 15px rgba(108, 92, 231, 0.3);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 6px 20px rgba(108, 92, 231, 0.4);
}

/* Trackers Grid */
.trackers-grid {
    display: flex;
    flex-direction: column;
    gap: 2rem;
    width: 100%;
    max-width: 800px;
}

.tracker-card {
    background: var(--bg-card);
    border-radius: 20px;
    padding: 2rem;
    box-shadow: var(--shadow);
    position: relative;
    overflow: hidden;
}

.tracker-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.tracker-title {
    font-size: 1.5rem;
    font-weight: 800;
    color: #2d3436;
}

.tracker-stats {
    font-size: 0.9rem;
    color: #636e72;
    background: #f1f2f6;
    padding: 0.5rem 1rem;
    border-radius: 12px;
}

.delete-tracker {
    background: none;
    border: none;
    color: #b2bec3;
    font-size: 1.2rem;
    cursor: pointer;
    transition: color 0.2s;
}

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

/* Days Grid */
.days-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(40px, 1fr));
    gap: 0.8rem;
}

.day-circle {
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background: #dfe6e9;
    display: flex;
    justify-content: center;
    align-items: center;
    font-weight: 600;
    color: #636e72;
    cursor: pointer;
    transition: all 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    user-select: none;
}

.day-circle:hover {
    transform: scale(1.1);
}

.day-circle.done {
    background: var(--success-color);
    color: white;
    box-shadow: 0 4px 10px rgba(0, 184, 148, 0.4);
}

.day-circle.missed {
    background: var(--danger-color);
    color: white;
    box-shadow: 0 4px 10px rgba(214, 48, 49, 0.4);
}

/* Modal */
.modal-container {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
    opacity: 1;
    transition: opacity 0.3s;
}

.modal-container.hidden {
    opacity: 0;
    pointer-events: none;
}

.modal {
    background: white;
    padding: 2rem;
    border-radius: 20px;
    width: 90%;
    max-width: 400px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.2);
    transform: translateY(0);
    transition: transform 0.3s;
}

.modal-container.hidden .modal {
    transform: translateY(20px);
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.close-btn {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
}

.form-group {
    margin-bottom: 1.5rem;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: #2d3436;
}

.form-group input {
    width: 100%;
    padding: 0.8rem;
    border: 2px solid #dfe6e9;
    border-radius: 10px;
    font-size: 1rem;
    font-family: inherit;
    transition: border-color 0.2s;
}

.form-group input:focus {
    outline: none;
    border-color: var(--primary-color);
}

.form-actions {
    text-align: right;
}