/* ===== GOOGLE-STYLE RESET & BASE STYLES ===== */
:root {
    --primary-blue: #1a73e8;
    --primary-blue-dark: #0d47a1;
    --primary-blue-light: #e8f0fe;
    --secondary-gray: #5f6368;
    --text-dark: #202124;
    --text-light: #5f6368;
    --text-white: #ffffff;
    --background-white: #ffffff;
    --background-light: #f8f9fa;
    --border-color: #dadce0;
    --card-shadow: 0 1px 2px 0 rgba(60,64,67,0.3), 0 1px 3px 1px rgba(60,64,67,0.15);
    --card-shadow-hover: 0 1px 3px 0 rgba(60,64,67,0.3), 0 4px 8px 3px rgba(60,64,67,0.15);
    --transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    --border-radius: 8px;
    --container-width: 1200px;
}

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

html {
    scroll-behavior: smooth;
}

body {
    font-family: 'Google Sans', 'Roboto', 'Segoe UI', Arial, sans-serif;
    line-height: 1.6;
    color: var(--text-dark);
    background-color: var(--background-light);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* ===== TYPOGRAPHY ===== */
h1, h2, h3, h4, h5, h6 {
    font-weight: 400;
    line-height: 1.3;
    margin-bottom: 1rem;
    color: var(--text-dark);
}

h1 {
    font-size: 2.5rem;
    font-weight: 300;
}

h2 {
    font-size: 2rem;
    font-weight: 400;
}

h3 {
    font-size: 1.5rem;
    font-weight: 500;
}

p {
    margin-bottom: 1rem;
    color: var(--text-light);
}

a {
    color: var(--primary-blue);
    text-decoration: none;
    transition: var(--transition);
}

a:hover {
    text-decoration: underline;
}

/* ===== LAYOUT & CONTAINERS ===== */
.container {
    width: 100%;
    max-width: var(--container-width);
    margin: 0 auto;
    padding: 0 24px;
}

.main-content {
    flex: 1;
    padding: 40px 0;
}

.section {
    padding: 60px 0;
}

.section-title {
    text-align: center;
    margin-bottom: 3rem;
}

.section-title h2 {
    margin-bottom: 0.5rem;
}

.section-title p {
    color: var(--secondary-gray);
    max-width: 600px;
    margin: 0 auto;
}

/* ===== HEADER & NAVIGATION ===== */
.header {
    background-color: var(--background-white);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    box-shadow: 0 1px 2px 0 rgba(60,64,67,0.1);
}

.header-container {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 24px;
}

.logo {
    display: flex;
    align-items: center;
    gap: 12px;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background-color: var(--primary-blue);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: var(--text-white);
    font-weight: 500;
    font-size: 1.2rem;
}

.logo-text h1 {
    font-size: 1.5rem;
    margin: 0;
    color: var(--text-dark);
    font-weight: 400;
}

.logo-text p {
    font-size: 0.875rem;
    color: var(--secondary-gray);
    margin: 0;
}

.nav-menu {
    display: flex;
    gap: 32px;
}

.nav-link {
    color: var(--text-dark);
    font-size: 0.95rem;
    padding: 8px 0;
    position: relative;
}

.nav-link:hover {
    color: var(--primary-blue);
    text-decoration: none;
}

.nav-link.active {
    color: var(--primary-blue);
}

.nav-link.active::after {
    content: '';
    position: absolute;
    bottom: -1px;
    left: 0;
    width: 100%;
    height: 2px;
    background-color: var(--primary-blue);
}

.mobile-menu-btn {
    display: none;
    background: none;
    border: none;
    color: var(--text-dark);
    font-size: 1.5rem;
    cursor: pointer;
    padding: 8px;
}

/* ===== TOOL CARDS ===== */
.tools-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 24px;
    margin-top: 2rem;
}

.tool-card {
    background-color: var(--background-white);
    border-radius: var(--border-radius);
    padding: 24px;
    box-shadow: var(--card-shadow);
    transition: var(--transition);
    border: 1px solid var(--border-color);
    text-decoration: none;
    display: block;
    color: inherit;
}

.tool-card:hover {
    box-shadow: var(--card-shadow-hover);
    border-color: var(--primary-blue-light);
    transform: translateY(-2px);
    text-decoration: none;
}

.tool-icon {
    width: 48px;
    height: 48px;
    background-color: var(--primary-blue-light);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    margin-bottom: 16px;
    color: var(--primary-blue);
    font-size: 1.5rem;
}

.tool-card h3 {
    margin-bottom: 8px;
    color: var(--text-dark);
}

.tool-card p {
    font-size: 0.95rem;
    color: var(--text-light);
    margin-bottom: 16px;
}

.tool-link {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    color: var(--primary-blue);
    font-weight: 500;
    font-size: 0.95rem;
}

/* ===== CALCULATOR FORMS ===== */
.calculator-container {
    max-width: 800px;
    margin: 0 auto;
}

.calculator-card {
    background-color: var(--background-white);
    border-radius: var(--border-radius);
    padding: 40px;
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border-color);
}

.form-group {
    margin-bottom: 24px;
}

.form-label {
    display: block;
    margin-bottom: 8px;
    color: var(--text-dark);
    font-weight: 500;
    font-size: 0.95rem;
}

.form-control {
    width: 100%;
    padding: 12px 16px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-family: inherit;
    transition: var(--transition);
    background-color: var(--background-white);
}

.form-control:focus {
    outline: none;
    border-color: var(--primary-blue);
    box-shadow: 0 0 0 2px var(--primary-blue-light);
}

.input-group {
    display: flex;
    gap: 12px;
}

.input-with-button {
    display: flex;
    gap: 8px;
}

.input-with-button .form-control {
    flex: 1;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    padding: 12px 24px;
    background-color: var(--primary-blue);
    color: var(--text-white);
    border: none;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
    font-family: inherit;
}

.btn:hover {
    background-color: var(--primary-blue-dark);
    text-decoration: none;
}

.btn-secondary {
    background-color: var(--background-light);
    color: var(--text-dark);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: #e8eaed;
}

.btn-sm {
    padding: 8px 16px;
    font-size: 0.875rem;
}

/* ===== RESULTS DISPLAY ===== */
.result-container {
    margin-top: 32px;
    padding: 24px;
    background-color: var(--primary-blue-light);
    border-radius: var(--border-radius);
    border-left: 4px solid var(--primary-blue);
}

.result-title {
    display: flex;
    align-items: center;
    gap: 12px;
    margin-bottom: 16px;
    color: var(--text-dark);
}

.result-value {
    font-size: 2.5rem;
    font-weight: 300;
    color: var(--primary-blue);
    margin-bottom: 8px;
}

.result-description {
    color: var(--text-light);
    font-size: 0.95rem;
}

/* ===== STUDY PLANNER ===== */
.planner-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin-top: 24px;
}

.planner-day {
    background-color: var(--background-white);
    border-radius: var(--border-radius);
    padding: 20px;
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border-color);
}

.planner-day h4 {
    margin-bottom: 16px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border-color);
    color: var(--text-dark);
}

.task-list {
    list-style: none;
}

.task-item {
    display: flex;
    align-items: flex-start;
    gap: 8px;
    padding: 8px 0;
    border-bottom: 1px solid var(--border-color-light);
}

.task-item:last-child {
    border-bottom: none;
}

.task-checkbox {
    margin-top: 4px;
}

.task-text {
    flex: 1;
    font-size: 0.95rem;
}

.task-delete {
    color: var(--secondary-gray);
    cursor: pointer;
    padding: 4px;
}

.task-delete:hover {
    color: #d93025;
}

.empty-state {
    text-align: center;
    padding: 40px 20px;
    color: var(--text-light);
}

.empty-state i {
    font-size: 3rem;
    margin-bottom: 16px;
    color: var(--border-color);
}

/* ===== TIMER ===== */
.timer-display {
    text-align: center;
    margin: 40px 0;
}

.timer-value {
    font-size: 4rem;
    font-weight: 300;
    color: var(--text-dark);
    font-family: 'Roboto Mono', monospace;
}

.timer-controls {
    display: flex;
    justify-content: center;
    gap: 16px;
    margin-top: 32px;
}

.timer-btn {
    width: 64px;
    height: 64px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    border: none;
    cursor: pointer;
    transition: var(--transition);
}

.timer-btn-start {
    background-color: #34a853;
    color: white;
}

.timer-btn-pause {
    background-color: #fbbc04;
    color: white;
}

.timer-btn-reset {
    background-color: #ea4335;
    color: white;
}

.timer-btn:hover {
    transform: scale(1.05);
}

/* ===== ABOUT PAGE ===== */
.about-content {
    max-width: 800px;
    margin: 0 auto;
}

.about-section {
    background-color: var(--background-white);
    border-radius: var(--border-radius);
    padding: 40px;
    margin-bottom: 32px;
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border-color);
}

.about-section h2 {
    margin-bottom: 20px;
    color: var(--text-dark);
}

.values-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin-top: 32px;
}

.value-card {
    text-align: center;
    padding: 24px;
    background-color: var(--primary-blue-light);
    border-radius: var(--border-radius);
}

.value-card i {
    font-size: 2.5rem;
    color: var(--primary-blue);
    margin-bottom: 16px;
}

/* ===== CONTACT FORM ===== */
.contact-form {
    max-width: 600px;
    margin: 0 auto;
}

.contact-info {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 24px;
    margin-top: 40px;
}

.contact-item {
    text-align: center;
    padding: 24px;
    background-color: var(--background-white);
    border-radius: var(--border-radius);
    box-shadow: var(--card-shadow);
    border: 1px solid var(--border-color);
}

.contact-item i {
    font-size: 2rem;
    color: var(--primary-blue);
    margin-bottom: 16px;
}

/* ===== FOOTER ===== */
.footer {
    background-color: var(--background-white);
    border-top: 1px solid var(--border-color);
    padding: 40px 0;
    margin-top: auto;
}

.footer-container {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 40px;
}

.footer-logo .logo-text h1 {
    font-size: 1.25rem;
}

.footer-links h4,
.footer-contact h4 {
    margin-bottom: 16px;
    color: var(--text-dark);
    font-weight: 500;
}

.footer-links ul {
    list-style: none;
}

.footer-links li {
    margin-bottom: 8px;
}

.footer-links a {
    color: var(--text-light);
}

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

.footer-bottom {
    text-align: center;
    margin-top: 40px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
    color: var(--text-light);
    font-size: 0.875rem;
}

.developer-credit {
    color: var(--primary-blue);
    font-weight: 500;
}

/* ===== RESPONSIVE DESIGN ===== */
@media (max-width: 768px) {
    .header-container {
        padding: 12px 16px;
    }
    
    .nav-menu {
        position: fixed;
        top: 72px;
        left: 0;
        right: 0;
        background-color: var(--background-white);
        flex-direction: column;
        padding: 20px;
        gap: 0;
        box-shadow: 0 2px 4px rgba(0,0,0,0.1);
        transform: translateY(-100%);
        opacity: 0;
        visibility: hidden;
        transition: var(--transition);
        z-index: 99;
    }
    
    .nav-menu.active {
        transform: translateY(0);
        opacity: 1;
        visibility: visible;
    }
    
    .nav-link {
        padding: 12px 0;
        border-bottom: 1px solid var(--border-color);
    }
    
    .nav-link:last-child {
        border-bottom: none;
    }
    
    .mobile-menu-btn {
        display: block;
    }
    
    .calculator-card {
        padding: 24px;
    }
    
    .timer-value {
        font-size: 3rem;
    }
    
    .input-group {
        flex-direction: column;
        gap: 16px;
    }
    
    .section {
        padding: 40px 0;
    }
}

@media (max-width: 480px) {
    .container {
        padding: 0 16px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.75rem;
    }
    
    .tools-grid {
        grid-template-columns: 1fr;
    }
    
    .timer-value {
        font-size: 2.5rem;
    }
}

/* ===== UTILITY CLASSES ===== */
.text-center {
    text-align: center;
}

.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mt-4 { margin-top: 2rem; }
.mt-5 { margin-top: 2.5rem; }

.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.mb-3 { margin-bottom: 1.5rem; }
.mb-4 { margin-bottom: 2rem; }
.mb-5 { margin-bottom: 2.5rem; }

.hidden {
    display: none !important;
}

.alert {
    padding: 16px;
    border-radius: var(--border-radius);
    margin-bottom: 20px;
    border-left: 4px solid;
}

.alert-success {
    background-color: #e6f4ea;
    border-left-color: #34a853;
    color: #137333;
}

.alert-error {
    background-color: #fce8e6;
    border-left-color: #ea4335;
    color: #c5221f;
}

.alert-info {
    background-color: #e8f0fe;
    border-left-color: var(--primary-blue);
    color: var(--primary-blue-dark);
}


.nav-menu {
  display: flex;
  align-items: center;
  gap: 20px;
}

/* Dropdown base */
.nav-dropdown {
  position: relative;
}

.dropdown-btn {
  background: none;
  border: none;
  cursor: pointer;
  font: inherit;
  color: inherit;
}

/* Dropdown menu */
.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 0;
  min-width: 240px;
  background: #ffffff;
  border: 1px solid #e5e7eb;
  border-radius: 8px;
  padding: 8px 0;
  box-shadow: 0 10px 25px rgba(0,0,0,0.08);
  display: none;
  z-index: 1000;
}

.dropdown-menu a {
  display: block;
  padding: 10px 14px;
  text-decoration: none;
  color: #111827;
  font-size: 14px;
}

.dropdown-menu a:hover {
  background: #f3f4f6;
}

/* Desktop hover */
@media (min-width: 768px) {
  .nav-dropdown:hover .dropdown-menu {
    display: block;
  }
}

.developer-credit {
  color: #1a73e8;
  text-decoration: none;
  font-weight: 500;
}

.developer-credit:hover {
  text-decoration: underline;
}