:root {
    --bg-color: #121212;
    --card-bg: #1e1e1e;
    --text-color: #e0e0e0;
    --accent-color: #ff4500;
    --accent-hover: #ff6a33;
    --secondary-color: #2c2c2c;
    --success-color: #4caf50;
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    align-items: center;
}

header {
    width: 100%;
    background-color: var(--card-bg);
    padding: 1.5rem;
    text-align: center;
    border-bottom: 3px solid var(--accent-color);
    margin-bottom: 2rem;
}

header h1 {
    color: var(--accent-color);
    letter-spacing: 2px;
}

main {
    width: 90%;
    max-width: 600px;
    text-align: center;
}

.page {
    display: none; /* Hidden by default */
    animation: fadeIn 0.3s ease-in-out;
}

.page.active {
    display: block; /* Only show if it has the 'active' class */
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

h2 {
    margin-bottom: 1.5rem;
    color: #ffffff;
}

.button-group {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 1rem;
}

button {
    cursor: pointer;
    border: none;
    border-radius: 8px;
    font-size: 1.1rem;
    font-weight: bold;
    transition: all 0.2s ease;
}

.btn-primary {
    background-color: var(--accent-color);
    color: white;
    padding: 1.2rem;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.btn-primary:hover {
    background-color: var(--accent-hover);
    transform: scale(1.02);
}

.btn-back {
    background-color: transparent;
    color: var(--text-color);
    border: 1px solid var(--secondary-color);
    padding: 0.5rem 1rem;
    margin-bottom: 1rem;
    font-size: 0.9rem;
}

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

.form-group {
    background-color: var(--card-bg);
    padding: 1.5rem;
    border-radius: 10px;
    margin-bottom: 1.5rem;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: bold;
    color: var(--accent-color);
}

select, input[type="number"] {
    width: 100%;
    padding: 0.8rem;
    border-radius: 5px;
    border: 1px solid var(--secondary-color);
    background-color: var(--bg-color);
    color: var(--text-color);
    font-size: 1rem;
}

.toggle-group, .time-buttons, .round-buttons {
    display: flex;
    flex-wrap: wrap;
    gap: 0.5rem;
    margin-top: 0.5rem;
}

.btn-toggle, .btn-time, .btn-round {
    flex: 1;
    min-width: 80px;
    padding: 0.8rem;
    background-color: var(--secondary-color);
    color: var(--text-color);
    font-size: 0.9rem;
}

.btn-toggle.active, .btn-time.active, .btn-round.active {
    background-color: var(--accent-color);
    color: white;
}

.btn-small {
    background-color: var(--secondary-color);
    color: var(--text-color);
    padding: 0.4rem 0.8rem;
    font-size: 0.8rem;
    margin-top: 0.5rem;
}

.info-box {
    background-color: #2a1a1a;
    border-left: 4px solid var(--accent-color);
    padding: 1rem;
    margin-bottom: 1.5rem;
    border-radius: 4px;
    text-align: left;
}

.btn-start {
    width: 100%;
    background-color: var(--success-color);
    color: white;
    padding: 1.2rem;
    font-size: 1.2rem;
    text-transform: uppercase;
}

.btn-start:hover {
    background-color: #43a047;
}

.btn-stop {
    background-color: #d32f2f;
    color: white;
    padding: 1rem 2rem;
}

.btn-stop:hover {
    background-color: #b71c1c;
}

.timer-display {
    background-color: var(--card-bg);
    padding: 2rem;
    border-radius: 15px;
    margin-bottom: 1.5rem;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 1rem;
}

.clock {
    font-size: 4rem;
    font-weight: bold;
    font-variant-numeric: tabular-nums;
    color: var(--accent-color);
}

#timer-phase {
    font-size: 1.5rem;
    font-weight: bold;
    color: var(--success-color);
}

#timer-phase.rest {
    color: #2196f3;
}