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

:root {
    --pomodoro-color: #e74c3c;
    --short-break-color: #27ae60;
    --long-break-color: #3498db;
    --background-dark: #1a1a2e;
    --background-light: #16213e;
    --text-primary: #ffffff;
    --text-secondary: #a0a0a0;
    --card-background: #0f3460;
    --border-radius: 12px;
    --transition: all 0.3s ease;
    --current-color: var(--pomodoro-color);
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, var(--background-dark) 0%, var(--background-light) 100%);
    min-height: 100vh;
    color: var(--text-primary);
    line-height: 1.6;
}

body.pomodoro-mode {
    --current-color: var(--pomodoro-color);
}

body.shortBreak-mode {
    --current-color: var(--short-break-color);
}

body.longBreak-mode {
    --current-color: var(--long-break-color);
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    padding: 20px;
}

header {
    text-align: center;
    padding: 20px 0;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 8px;
    color: var(--current-color);
    transition: var(--transition);
}

header .subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

main {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 30px;
    padding: 20px 0;
}

.timer-container {
    background: var(--card-background);
    border-radius: var(--border-radius);
    padding: 40px;
    width: 100%;
    max-width: 500px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
}

.mode-tabs {
    display: flex;
    gap: 10px;
    margin-bottom: 40px;
    justify-content: center;
    flex-wrap: wrap;
}

.mode-tab {
    background: transparent;
    border: 2px solid var(--text-secondary);
    color: var(--text-secondary);
    padding: 10px 20px;
    border-radius: 25px;
    cursor: pointer;
    font-size: 0.95rem;
    font-weight: 600;
    transition: var(--transition);
}

.mode-tab:hover {
    border-color: var(--current-color);
    color: var(--current-color);
}

.mode-tab.active {
    background: var(--current-color);
    border-color: var(--current-color);
    color: var(--text-primary);
}

.timer-display {
    text-align: center;
    font-size: 7rem;
    font-weight: 700;
    font-family: 'Courier New', Courier, monospace;
    margin-bottom: 40px;
    color: var(--current-color);
    transition: var(--transition);
    display: flex;
    justify-content: center;
    align-items: center;
}

.timer-display .colon {
    animation: blink 1s infinite;
}

@keyframes blink {
    0%, 50% { opacity: 1; }
    51%, 100% { opacity: 0.3; }
}

.timer-controls {
    display: flex;
    gap: 15px;
    justify-content: center;
    margin-bottom: 30px;
}

.control-btn {
    padding: 15px 40px;
    border: none;
    border-radius: 30px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: var(--transition);
    text-transform: uppercase;
    letter-spacing: 1px;
}

.control-btn.primary {
    background: var(--current-color);
    color: var(--text-primary);
}

.control-btn.primary:hover {
    transform: scale(1.05);
    box-shadow: 0 5px 20px rgba(231, 76, 60, 0.4);
}

.control-btn.secondary {
    background: transparent;
    border: 2px solid var(--text-secondary);
    color: var(--text-secondary);
}

.control-btn.secondary:hover {
    border-color: var(--text-primary);
    color: var(--text-primary);
}

.session-info {
    display: flex;
    justify-content: space-around;
    padding-top: 20px;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
}

.session-counter,
.cycle-indicator {
    text-align: center;
}

.session-info .label {
    display: block;
    font-size: 0.85rem;
    color: var(--text-secondary);
    margin-bottom: 8px;
}

.session-counter .count {
    font-size: 2rem;
    font-weight: 700;
    color: var(--current-color);
}

.cycle-dots {
    display: flex;
    gap: 8px;
    justify-content: center;
}

.cycle-dots .dot {
    width: 12px;
    height: 12px;
    border-radius: 50%;
    background: var(--text-secondary);
    transition: var(--transition);
}

.cycle-dots .dot.completed {
    background: var(--current-color);
}

.cycle-dots .dot.active {
    background: var(--current-color);
    box-shadow: 0 0 10px var(--current-color);
}

.settings-container {
    width: 100%;
    max-width: 500px;
}

.settings-toggle {
    display: flex;
    align-items: center;
    gap: 8px;
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-size: 1rem;
    padding: 10px;
    transition: var(--transition);
}

.settings-toggle:hover {
    color: var(--text-primary);
}

.settings-panel {
    background: var(--card-background);
    border-radius: var(--border-radius);
    padding: 25px;
    margin-top: 15px;
    box-shadow: 0 10px 40px rgba(0, 0, 0, 0.3);
}

.settings-panel.hidden {
    display: none;
}

.settings-panel h3 {
    margin-bottom: 20px;
    color: var(--current-color);
}

.setting-group {
    margin-bottom: 15px;
}

.setting-group label {
    display: block;
    margin-bottom: 5px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.setting-group input[type="number"] {
    width: 100%;
    padding: 12px;
    border: 2px solid rgba(255, 255, 255, 0.1);
    border-radius: 8px;
    background: rgba(0, 0, 0, 0.2);
    color: var(--text-primary);
    font-size: 1rem;
    transition: var(--transition);
}

.setting-group input[type="number"]:focus {
    outline: none;
    border-color: var(--current-color);
}

.checkbox-group label {
    display: flex;
    align-items: center;
    gap: 10px;
    cursor: pointer;
}

.checkbox-group input[type="checkbox"] {
    width: 20px;
    height: 20px;
    cursor: pointer;
    accent-color: var(--current-color);
}

.save-btn {
    width: 100%;
    padding: 12px;
    background: var(--current-color);
    border: none;
    border-radius: 8px;
    color: var(--text-primary);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin-top: 10px;
    transition: var(--transition);
}

.save-btn:hover {
    transform: scale(1.02);
}

.fullscreen-btn {
    position: fixed;
    bottom: 80px;
    right: 20px;
    background: var(--card-background);
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    color: var(--text-secondary);
    transition: var(--transition);
    box-shadow: 0 5px 20px rgba(0, 0, 0, 0.3);
}

.fullscreen-btn:hover {
    color: var(--text-primary);
    transform: scale(1.1);
}

.fullscreen-btn .hidden {
    display: none;
}

footer {
    text-align: center;
    padding: 20px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

footer a {
    color: var(--current-color);
    text-decoration: none;
    transition: var(--transition);
}

footer a:hover {
    text-decoration: underline;
}

/* Fullscreen styles */
body:fullscreen .app-container,
body:-webkit-full-screen .app-container {
    background: linear-gradient(135deg, var(--background-dark) 0%, var(--background-light) 100%);
}

body:fullscreen .timer-display,
body:-webkit-full-screen .timer-display {
    font-size: 12rem;
}

body:fullscreen .settings-container,
body:-webkit-full-screen .settings-container {
    display: none;
}

body:fullscreen .fullscreen-btn .expand-icon,
body:-webkit-full-screen .fullscreen-btn .expand-icon {
    display: none;
}

body:fullscreen .fullscreen-btn .compress-icon,
body:-webkit-full-screen .fullscreen-btn .compress-icon {
    display: block;
}

/* Mobile responsiveness */
@media (max-width: 600px) {
    header h1 {
        font-size: 1.8rem;
    }

    .timer-container {
        padding: 25px 20px;
    }

    .mode-tab {
        padding: 8px 15px;
        font-size: 0.85rem;
    }

    .timer-display {
        font-size: 4rem;
    }

    .control-btn {
        padding: 12px 30px;
        font-size: 1rem;
    }

    .session-info {
        flex-direction: column;
        gap: 20px;
    }

    .fullscreen-btn {
        bottom: 70px;
        right: 15px;
        width: 45px;
        height: 45px;
    }
}

@media (max-width: 400px) {
    .timer-display {
        font-size: 3.5rem;
    }

    .mode-tabs {
        gap: 5px;
    }

    .mode-tab {
        padding: 6px 12px;
        font-size: 0.8rem;
    }

    .control-btn {
        padding: 10px 25px;
    }
}

/* Animation for timer running */
@keyframes pulse {
    0%, 100% { transform: scale(1); }
    50% { transform: scale(1.02); }
}

.timer-running .timer-display {
    animation: pulse 2s infinite;
}

/* Notification animation */
@keyframes shake {
    0%, 100% { transform: translateX(0); }
    25% { transform: translateX(-5px); }
    75% { transform: translateX(5px); }
}

.timer-complete {
    animation: shake 0.5s ease-in-out 3;
}