:root {
    --primary-color: #2563EB;
    --primary-hover: #1D4ED8;
    --primary-light: #EFF6FF;
    --secondary-color: #64748B;
    --secondary-hover: #475569;
    --secondary-light: #F1F5F9;
    --danger-color: #EF4444;
    --danger-light: #FEE2E2;
    --success-color: #10B981;
    --success-light: #D1FAE5;
    --warning-color: #F59E0B;
    --warning-light: #FEF3C7;
    --background-color: #F8FAFC;
    --card-bg: #FFFFFF;
    --text-main: #1E293B;
    --text-muted: #64748B;
    --border-color: #E2E8F0;
    --shadow-sm: 0 1px 2px 0 rgba(0, 0, 0, 0.05);
    --shadow-md: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -1px rgba(0, 0, 0, 0.06);
    --shadow-lg: 0 10px 15px -3px rgba(0, 0, 0, 0.1), 0 4px 6px -2px rgba(0, 0, 0, 0.05);
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 18px;

    /* Mode Colors */
    --focus-color: #2563EB;
    --focus-light: #EFF6FF;
    --short-color: #10B981;
    --short-light: #D1FAE5;
    --long-color: #8B5CF6;
    --long-light: #EDE9FE;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    font-family: 'Inter', sans-serif;
}

body {
    background-color: var(--background-color);
    color: var(--text-main);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
    transition: background-color 0.5s ease;
}

/* ========== Header ========== */
.header {
    background-color: var(--card-bg);
    padding: 1.25rem 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow-sm);
    position: sticky;
    top: 0;
    z-index: 100;
}

.logo {
    display: flex;
    align-items: center;
    gap: 0.75rem;
    font-size: 1.5rem;
    font-weight: 700;
    color: var(--primary-color);
}

.nav ul {
    list-style: none;
    display: flex;
    gap: 2.5rem;
}

.nav a {
    text-decoration: none;
    color: var(--text-muted);
    font-weight: 500;
    transition: color 0.2s ease;
}

.nav a:hover,
.nav a.active {
    color: var(--primary-color);
}

.header-contact {
    display: flex;
    gap: 1.5rem;
}

.contact-link {
    text-decoration: none;
    color: var(--text-muted);
    display: flex;
    align-items: center;
    gap: 0.5rem;
    font-size: 0.9rem;
    font-weight: 500;
    transition: color 0.2s ease;
}

.contact-link:hover {
    color: var(--primary-color);
}

/* ========== Main ========== */
.main-content {
    flex: 1;
    display: flex;
    justify-content: center;
    align-items: flex-start;
    padding: 3rem 1rem;
}

.timer-container {
    max-width: 520px;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 2rem;
}

/* ========== Mode Tabs ========== */
.mode-tabs {
    display: flex;
    gap: 0.5rem;
    background-color: var(--card-bg);
    padding: 0.4rem;
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-md);
}

.mode-tab {
    flex: 1;
    padding: 0.875rem 1rem;
    border: none;
    background-color: transparent;
    border-radius: var(--radius-md);
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    white-space: nowrap;
    transition: all 0.3s ease;
}

.mode-tab:hover {
    background-color: var(--secondary-light);
    color: var(--text-main);
}

.mode-tab.active[data-mode="focus"] {
    background-color: var(--focus-color);
    color: white;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.mode-tab.active[data-mode="short"] {
    background-color: var(--short-color);
    color: white;
    box-shadow: 0 4px 12px rgba(16, 185, 129, 0.3);
}

.mode-tab.active[data-mode="long"] {
    background-color: var(--long-color);
    color: white;
    box-shadow: 0 4px 12px rgba(139, 92, 246, 0.3);
}

/* ========== Timer Card ========== */
.card {
    background-color: var(--card-bg);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-lg);
    padding: 2.5rem;
    transition: box-shadow 0.3s ease;
}

.card:hover {
    box-shadow: 0 20px 25px -5px rgba(0, 0, 0, 0.1), 0 10px 10px -5px rgba(0, 0, 0, 0.04);
}

.timer-card {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 2rem;
}

/* ========== Circular Timer ========== */
.timer-ring-wrapper {
    position: relative;
    width: 260px;
    height: 260px;
}

.timer-ring {
    width: 100%;
    height: 100%;
    transform: rotate(-90deg);
}

.ring-bg {
    fill: none;
    stroke: var(--border-color);
    stroke-width: 8;
}

.ring-progress {
    fill: none;
    stroke: var(--focus-color);
    stroke-width: 8;
    stroke-linecap: round;
    stroke-dasharray: 753.98; /* 2 * π * 120 */
    stroke-dashoffset: 0;
    transition: stroke-dashoffset 0.5s ease, stroke 0.5s ease;
}

.timer-display {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    text-align: center;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.timer-time {
    font-size: 4rem;
    font-weight: 800;
    color: var(--text-main);
    letter-spacing: -2px;
    line-height: 1;
    font-variant-numeric: tabular-nums;
}

.timer-label {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-muted);
    text-transform: uppercase;
    letter-spacing: 0.08em;
}

/* Session Counter */
.session-counter {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--text-muted);
    background-color: var(--secondary-light);
    padding: 0.5rem 1.25rem;
    border-radius: 9999px;
}

/* ========== Controls ========== */
.timer-controls {
    display: flex;
    gap: 0.75rem;
    width: 100%;
    justify-content: center;
}

.btn {
    padding: 0.875rem 1.75rem;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.5rem;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
}

.btn:active {
    transform: scale(0.96);
}

.btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.btn-large {
    padding: 1rem 2.5rem;
    font-size: 1.05rem;
}

.btn-primary {
    background-color: var(--primary-color);
    color: white;
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.3);
}

.btn-secondary {
    background-color: var(--secondary-light);
    color: var(--text-main);
}

.btn-secondary:hover:not(:disabled) {
    background-color: #E2E8F0;
}

.btn-danger-outline {
    background-color: transparent;
    color: var(--text-muted);
    border: 1px solid var(--border-color);
}

.btn-danger-outline:hover:not(:disabled) {
    background-color: var(--danger-light);
    border-color: var(--danger-color);
    color: var(--danger-color);
}

/* ========== Settings Card ========== */
.settings-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1.5rem;
}

.settings-header h3 {
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-main);
    display: flex;
    align-items: center;
    gap: 0.5rem;
}

.settings-hint {
    font-size: 0.8rem;
    font-weight: 500;
    color: var(--text-muted);
}

.settings-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 1.5rem;
}

.setting-item {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 0.75rem;
}

.setting-item label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-muted);
}

.stepper {
    display: flex;
    align-items: center;
    background-color: var(--background-color);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-sm);
    overflow: hidden;
}

.stepper-btn {
    width: 40px;
    height: 44px;
    border: none;
    background-color: transparent;
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.2s ease;
    font-size: 0.8rem;
}

.stepper-btn:hover {
    background-color: var(--primary-light);
    color: var(--primary-color);
}

.stepper-btn:active {
    transform: scale(0.9);
}

.stepper-input {
    width: 48px;
    height: 44px;
    border: none;
    background-color: transparent;
    text-align: center;
    font-size: 1.1rem;
    font-weight: 700;
    color: var(--text-main);
    outline: none;
    /* Hide arrows */
    -moz-appearance: textfield;
}

.stepper-input::-webkit-outer-spin-button,
.stepper-input::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

/* ========== Toast ========== */
.toast {
    position: fixed;
    bottom: 2rem;
    right: 2rem;
    background-color: var(--text-main);
    color: white;
    padding: 1rem 1.5rem;
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    gap: 0.75rem;
    box-shadow: var(--shadow-lg);
    z-index: 1000;
    transition: all 0.4s cubic-bezier(0.68, -0.55, 0.265, 1.55);
    transform: translateY(150%);
    opacity: 0;
}

.toast.show {
    transform: translateY(0);
    opacity: 1;
}

.toast.success i { color: var(--success-color); }
.toast.danger i { color: var(--danger-color); }
.toast.info i { color: var(--primary-color); }

/* ========== Footer ========== */
.footer {
    background-color: var(--card-bg);
    padding: 2rem;
    text-align: center;
    border-top: 1px solid var(--border-color);
    margin-top: auto;
}

.text-danger { color: var(--danger-color); }

.footer-contact {
    display: flex;
    justify-content: center;
    gap: 2rem;
    font-size: 0.95rem;
    margin-top: 1rem;
}

.footer-contact a {
    color: var(--text-muted);
    text-decoration: none;
    transition: color 0.2s ease;
}

.footer-contact a:hover {
    color: var(--primary-color);
}

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

@keyframes pulse {
    0%, 100% { transform: translate(-50%, -50%) scale(1); }
    50% { transform: translate(-50%, -50%) scale(1.03); }
}

.timer-display.pulsing {
    animation: pulse 1.5s ease-in-out infinite;
}