:root {
    --bg-color: #ffffff;
    --font-color: #1a1a1a;
    --primary-accent: #007aff;
    --primary-accent-hover: #0056b3;
    --border-color: #e0e0e0;
    --panel-bg: #f9f9f9;
    --disabled-color: #c7c7c7;
    --red-accent: #d92d20;
    --green-accent: #058f3a;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji";
    background-color: var(--bg-color);
    color: var(--font-color);
    margin: 0;
    padding: 2rem;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    gap: 1.5rem;
    min-height: 100vh;
    box-sizing: border-box;
}

header {
    position: absolute;
    top: 1.5rem;
    left: 1.5rem;
}

.back-link {
    text-decoration: none;
    color: var(--primary-accent);
    font-size: 0.9rem;
}

.back-link:hover {
    text-decoration: underline;
}

.timer-container {
    width: 100%;
    max-width: 480px;
    background: var(--bg-color);
    border-radius: 12px;
    box-shadow: 0 8px 32px rgba(0,0,0,0.1);
    border: 1px solid var(--border-color);
    overflow: hidden;
}

.timer-nav {
    display: flex;
    background-color: var(--panel-bg);
    border-bottom: 1px solid var(--border-color);
}

.nav-button {
    flex-grow: 1;
    padding: 1rem;
    font-size: 1rem;
    font-weight: 500;
    border: none;
    background: transparent;
    cursor: pointer;
    color: var(--font-color);
    border-bottom: 2px solid transparent;
    transition: background-color 0.2s, border-color 0.2s;
}

.nav-button:hover {
    background-color: #f0f0f0;
}

.nav-button.active {
    color: var(--primary-accent);
    border-bottom-color: var(--primary-accent);
}

.panel {
    display: none;
    padding: 2rem;
    text-align: center;
}

.panel.active {
    display: block;
}

.time-display {
    font-size: 3.5rem;
    font-weight: 300;
    font-family: "SF Mono", "Fira Code", "Consolas", monospace;
    letter-spacing: 1px;
    margin-bottom: 1.5rem;
}

.controls {
    display: flex;
    justify-content: center;
    gap: 1rem;
    margin-bottom: 1.5rem;
}

.controls button {
    padding: 0.75rem 1.5rem;
    font-size: 1rem;
    font-weight: 500;
    border-radius: 8px;
    border: 1px solid var(--border-color);
    background-color: var(--bg-color);
    cursor: pointer;
    transition: background-color 0.2s;
}

.controls button:hover {
    background-color: #f0f0f0;
}

.controls button:disabled {
    cursor: not-allowed;
    color: var(--disabled-color);
    background-color: var(--panel-bg);
}

#stopwatch-start, #countdown-start, #interval-start {
    background-color: var(--green-accent);
    color: white;
    border-color: var(--green-accent);
}

#stopwatch-stop, #countdown-stop, #interval-stop {
    background-color: var(--red-accent);
    color: white;
    border-color: var(--red-accent);
}

.laps-list {
    list-style-type: none;
    padding: 0;
    max-height: 200px;
    overflow-y: auto;
    text-align: left;
    background: var(--panel-bg);
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.laps-list li {
    padding: 0.75rem 1rem;
    display: flex;
    justify-content: space-between;
    font-family: "SF Mono", "Fira Code", "Consolas", monospace;
}

.laps-list li:not(:last-child) {
    border-bottom: 1px solid var(--border-color);
}

.input-group, .interval-setup {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 0.5rem;
    margin-bottom: 1.5rem;
}

.interval-setup {
    flex-direction: column;
    gap: 1rem;
}

.input-group input {
    width: 60px;
    font-size: 1.2rem;
    text-align: center;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    padding: 0.5rem;
}

.interval-display-area {
    margin-bottom: 1.5rem;
}

.interval-status {
    font-size: 1.5rem;
    font-weight: 600;
    margin-bottom: 0.5rem;
    text-transform: uppercase;
}

.interval-round-display {
    font-size: 1rem;
    color: #666;
}

@media (max-width: 520px) {
    body {
        padding: 0;
        align-items: stretch;
    }
    .timer-container {
        border-radius: 0;
        border: none;
        box-shadow: none;
        max-width: 100%;
        min-height: 100vh;
    }
    .time-display {
        font-size: 2.8rem;
    }
    .controls button {
        padding: 0.75rem 1rem;
    }
    header {
        position: static;
        padding: 1rem;
        text-align: center;
        background: var(--panel-bg);
    }
}

.footer {
    text-align: center;
    padding: 16px 0 24px;
    color: rgba(26, 26, 26, 0.7);
    font-size: 0.9rem;
}

.support-link {
    color: inherit;
    font-weight: 600;
    text-decoration: none;
}

.support-link:hover {
    text-decoration: underline;
}