:root {
    --primary-color: #4361ee;
    --primary-hover: #3a56d4;
    --text-color: #333;
    --bg-color: #f5f7fa;
    --card-bg: #ffffff;
    --card-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    --border-color: #e0e6ed;
    --input-bg: #f5f7fa;
    --chart-grid: #e0e6ed;
    --good-sleep: #4cc9f0;
    --bad-sleep: #f72585;
    --ideal-sleep: #4895ef;
    --animation-duration: 0.4s;
}

[data-theme="dark"] {
    --primary-color: #4cc9f0;
    --primary-hover: #3db8df;
    --text-color: #e0e6ed;
    --bg-color: #121212;
    --card-bg: #1e1e1e;
    --card-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
    --border-color: #333;
    --input-bg: #2d2d2d;
    --chart-grid: #333;
    --good-sleep: #4cc9f0;
    --bad-sleep: #f72585;
    --ideal-sleep: #4895ef;
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideInUp {
    from { 
        transform: translateY(20px);
        opacity: 0;
    }
    to { 
        transform: translateY(0);
        opacity: 1;
    }
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.05); }
    100% { transform: scale(1); }
}

@keyframes bounce {
    0%, 20%, 50%, 80%, 100% { transform: translateY(0); }
    40% { transform: translateY(-15px); }
    60% { transform: translateY(-5px); }
}

@keyframes scaleIn {
    from { transform: scale(0.9); opacity: 0; }
    to { transform: scale(1); opacity: 1; }
}

@keyframes modalFade {
    from {opacity: 0; transform: translateY(-20px);}
    to {opacity: 1; transform: translateY(0);}
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
    transition: background-color 0.3s, color 0.3s, box-shadow 0.3s;
}

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    padding: 20px;
    min-height: 100vh;
}

/* Welcome Overlay */
.overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: var(--bg-color);
    z-index: 1000;
    display: flex;
    justify-content: center;
    align-items: center;
    animation: fadeIn 1s;
}

.overlay-content {
    text-align: center;
    padding: 20px;
    max-width: 500px;
}

.welcome-title {
    font-size: 3rem;
    color: var(--primary-color);
    margin-bottom: 20px;
    animation: slideInUp 0.8s ease-out forwards;
}

.welcome-subtitle {
    font-size: 1.2rem;
    margin-bottom: 40px;
    color: var(--text-color);
    opacity: 0.9;
    animation: slideInUp 0.8s ease-out forwards;
    animation-delay: 0.2s;
    opacity: 0;
    animation-fill-mode: forwards;
}

.welcome-buttons {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-top: 30px;
}

.welcome-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 30px;
    padding: 14px 30px;
    font-size: 1.1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 4px 12px rgba(67, 97, 238, 0.3);
    animation: slideInUp 0.6s ease-out forwards;
    opacity: 0;
    animation-fill-mode: forwards;
}

.welcome-btn:nth-child(1) {
    animation-delay: 0.4s;
}

.welcome-btn:nth-child(2) {
    animation-delay: 0.6s;
}

.welcome-btn:nth-child(3) {
    animation-delay: 0.8s;
}

.welcome-btn:hover {
    background-color: var(--primary-hover);
    transform: translateY(-3px);
    box-shadow: 0 6px 18px rgba(67, 97, 238, 0.4);
}

.welcome-btn-outline {
    background-color: transparent;
    border: 2px solid var(--primary-color);
    color: var(--primary-color);
    box-shadow: none;
}

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

.container {
    max-width: 800px;
    margin: 0 auto;
    padding: 20px;
    animation: fadeIn var(--animation-duration);
}

/* Cards with animation */
#calculator, 
.result-container, 
.sleep-chart-container,
.recommendations,
.history-container {
    background-color: var(--card-bg);
    border-radius: 12px;
    box-shadow: var(--card-shadow);
    padding: 30px;
    margin-bottom: 30px;
    transform: translateY(20px);
    opacity: 0;
    animation: slideInUp 0.5s ease-out forwards;
}

#calculator {
    animation-delay: 0.1s;
}

.result-container {
    animation-delay: 0.2s;
}

.sleep-chart-container {
    animation-delay: 0.3s;
}

.recommendations {
    animation-delay: 0.4s;
}

.history-container {
    animation-delay: 0.5s;
}

header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 30px;
    animation: fadeIn 0.8s;
}

h1 {
    font-size: 2.2rem;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 10px;
}

h2 {
    color: var(--primary-color);
    margin-bottom: 15px;
    font-size: 1.6rem;
}

h3 {
    margin-bottom: 10px;
    font-size: 1.3rem;
}

.auth-container {
    display: flex;
    align-items: center;
}

#auth-status {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-right: 15px;
}

.auth-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 6px;
    padding: 8px 16px;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s;
}

.auth-btn:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.toggle-container {
    display: flex;
    align-items: center;
}

.theme-toggle {
    background: none;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    color: var(--text-color);
    margin-left: 10px;
    transition: transform 0.3s ease;
}

.theme-toggle:hover {
    transform: rotate(15deg);
}

.input-container {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 20px;
}

.input-group {
    display: flex;
    flex-direction: column;
    text-align: left;
    transition: transform 0.3s;
}

.input-group:hover {
    transform: translateY(-3px);
}

label {
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-color);
}

input[type="number"],
input[type="email"],
input[type="password"],
select {
    padding: 10px 15px;
    border: 1px solid var(--border-color);
    border-radius: 6px;
    background-color: var(--input-bg);
    color: var(--text-color);
    font-size: 1rem;
    transition: all 0.3s;
}

input[type="number"]:focus,
input[type="email"]:focus,
input[type="password"]:focus,
select:focus {
    outline: 2px solid var(--primary-color);
    border-color: transparent;
    transform: scale(1.02);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

button {
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 6px;
    padding: 12px 24px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    margin: 20px 0;
    transition: all 0.3s;
}

button:hover {
    background-color: var(--primary-hover);
    transform: translateY(-3px);
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.15);
}

button:active {
    transform: translateY(-1px);
    box-shadow: 0 2px 6px rgba(0, 0, 0, 0.1);
}

#calculate-btn {
    background-image: linear-gradient(135deg, var(--primary-color), var(--ideal-sleep));
    background-size: 200% 100%;
    transition: all 0.3s ease;
}

#calculate-btn:hover {
    background-position: 100% 0;
}

.sync-btn {
    background-color: var(--good-sleep);
    margin-left: 10px;
    transition: all 0.3s;
}

.sync-btn:hover {
    background-color: var(--ideal-sleep);
    transform: translateY(-3px);
}

#user-email {
    font-size: 0.9rem;
    color: var(--text-color);
}

#result {
    font-size: 1.1rem;
    line-height: 1.5;
    padding: 15px;
    border-radius: 8px;
    background-color: var(--input-bg);
    margin: 15px 0;
    transition: all 0.3s;
    animation: scaleIn 0.5s;
}

.sleep-chart {
    width: 100%;
    height: 250px;
    margin: 20px 0;
    position: relative;
}

.chart-bar {
    position: absolute;
    bottom: 30px;
    width: 30px;
    background-color: var(--good-sleep);
    border-radius: 4px 4px 0 0;
    transition: height 1s cubic-bezier(0.2, 0.8, 0.2, 1);
    animation: slideInUp 0.8s;
}

.chart-bar.below-threshold {
    background-color: var(--bad-sleep);
}

.chart-bar:hover {
    opacity: 0.8;
    transform: scaleX(1.1);
}

.chart-label {
    position: absolute;
    bottom: 0;
    transform: translateX(-50%);
    font-size: 0.85rem;
    font-weight: 600;
}

.chart-grid {
    position: absolute;
    width: 100%;
    height: 1px;
    background-color: var(--chart-grid);
}

.chart-grid-label {
    position: absolute;
    right: 0;
    transform: translateY(-50%);
    font-size: 0.75rem;
    color: var(--text-color);
    opacity: 0.7;
}

.ideal-line {
    position: absolute;
    width: 100%;
    height: 2px;
    background-color: var(--ideal-sleep);
    z-index: 1;
    animation: fadeIn 1s;
}

.quality-rating {
    display: flex;
    gap: 5px;
    margin: 10px 0;
}

.star {
    cursor: pointer;
    font-size: 1.5rem;
    color: #ccc;
    transition: all 0.3s;
}

.star:hover {
    transform: scale(1.2);
}

.star.active {
    color: gold;
    animation: pulse 0.5s;
}

.history-entry {
    display: flex;
    justify-content: space-between;
    padding: 15px;
    border-radius: 8px;
    margin: 10px 0;
    background-color: var(--input-bg);
    transition: all 0.3s;
    cursor: pointer;
    border-left: 3px solid var(--primary-color);
}

.history-entry:hover {
    transform: translateX(5px);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.1);
}

.history-actions {
    display: flex;
    justify-content: center;
    gap: 10px;
    margin-top: 15px;
}

/* Modal Styles */
.modal {
    display: none;
    position: fixed;
    z-index: 1000;
    left: 0;
    top: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    animation: fadeIn 0.3s;
}

.modal-content {
    background-color: var(--card-bg);
    margin: 15% auto;
    padding: 25px;
    border-radius: 10px;
    box-shadow: var(--card-shadow);
    width: 80%;
    max-width: 400px;
    position: relative;
    animation: modalFade 0.4s;
}

.close {
    position: absolute;
    right: 20px;
    top: 15px;
    color: var(--text-color);
    font-size: 28px;
    font-weight: bold;
    cursor: pointer;
    transition: all 0.3s;
}

.close:hover {
    color: var(--primary-color);
    transform: rotate(90deg);
}

.error-message {
    color: #f72585;
    margin: 10px 0;
    font-size: 0.9rem;
    display: none;
    animation: shake 0.5s;
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    10%, 30%, 50%, 70%, 90% { transform: translateX(-5px); }
    20%, 40%, 60%, 80% { transform: translateX(5px); }
}

/* Recommendations section */
#recommendations-list ul {
    padding-left: 20px;
}

#recommendations-list li {
    margin-bottom: 10px;
    position: relative;
    padding-left: 10px;
    animation: fadeIn 0.5s;
}

#recommendations-list li::before {
    content: "•";
    color: var(--primary-color);
    font-weight: bold;
    position: absolute;
    left: -10px;
}

/* Responsive adjustments */
@media (max-width: 768px) {
    .container {
        padding: 10px;
    }
    
    header {
        flex-direction: column;
        text-align: center;
        gap: 15px;
    }
    
    .auth-container {
        flex-direction: column;
        gap: 10px;
        margin-top: 10px;
    }
    
    #auth-status {
        margin-right: 0;
        margin-bottom: 10px;
    }
    
    #calculator, 
    .result-container, 
    .sleep-chart-container,
    .recommendations,
    .history-container {
        padding: 15px;
    }
    
    .input-container {
        grid-template-columns: 1fr;
    }
    
    .modal-content {
        width: 90%;
        margin: 30% auto;
    }
    
    .welcome-title {
        font-size: 2.5rem;
    }
    
    .welcome-buttons {
        width: 100%;
    }
}

/* Auth Page Styles */
.auth-page {
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--bg-color);
    background-image: linear-gradient(135deg, var(--bg-color), var(--primary-color) 150%);
    padding: 20px;
}

.auth-container-page {
    width: 100%;
    max-width: 450px;
    animation: fadeIn 0.8s;
}

.auth-card {
    background-color: var(--card-bg);
    border-radius: 12px;
    box-shadow: var(--card-shadow);
    padding: 30px;
    animation: scaleIn 0.5s;
}

.auth-header {
    text-align: center;
    margin-bottom: 25px;
}

.auth-header h1 {
    color: var(--primary-color);
    font-size: 2.2rem;
    margin-bottom: 10px;
    animation: slideInUp 0.5s;
}

.auth-subtitle {
    color: var(--text-color);
    opacity: 0.8;
    font-size: 1rem;
    animation: slideInUp 0.6s;
}

.auth-tabs {
    display: flex;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

.auth-tab-btn {
    flex: 1;
    background: none;
    border: none;
    padding: 12px;
    font-size: 1rem;
    font-weight: 600;
    color: var(--text-color);
    opacity: 0.7;
    cursor: pointer;
    transition: all 0.3s;
    border-bottom: 2px solid transparent;
}

.auth-tab-btn:hover {
    opacity: 1;
    background-color: rgba(0, 0, 0, 0.03);
}

.auth-tab-btn.active {
    color: var(--primary-color);
    opacity: 1;
    border-bottom: 2px solid var(--primary-color);
}

.auth-tab-content {
    display: none;
    animation: fadeIn 0.5s;
}

.auth-tab-content.active {
    display: block;
}

.auth-form {
    margin-bottom: 20px;
}

.auth-form .input-group {
    margin-bottom: 20px;
}

.password-hint {
    display: block;
    margin-top: 5px;
    font-size: 0.8rem;
    color: var(--text-color);
    opacity: 0.7;
}

.auth-submit-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--primary-color);
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s;
    margin-top: 10px;
}

.auth-submit-btn:hover {
    background-color: var(--primary-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.1);
}

.auth-options {
    text-align: center;
    margin-top: 20px;
    padding-top: 20px;
    border-top: 1px solid var(--border-color);
}

.guest-link {
    color: var(--primary-color);
    text-decoration: none;
    font-weight: 500;
    transition: all 0.3s;
}

.guest-link:hover {
    text-decoration: underline;
    opacity: 0.9;
}

.auth-links {
    margin-top: 15px;
    text-align: center;
}

.auth-link {
    color: var(--primary-color);
    text-decoration: none;
    font-size: 0.9rem;
    transition: color 0.3s;
}

.auth-link:hover {
    text-decoration: underline;
    color: var(--primary-hover);
}