/* Reset and Base Styles */
:root {
    /* Primary Color Palette */
    --primary-color: #2196F3;
    --success-color: #4CAF50;
    --warning-color: #FFC107;
    --danger-color: #F44336;
    --accent-color: #9C27B0;
    
    /* Light Theme */
    --background-color: #f9f9f9;
    --card-color: #ffffff;
    --text-color: #333333;
    --text-secondary: #666666;
    --border-color: #e0e0e0;
    --shadow-color: rgba(0, 0, 0, 0.1);
    
    /* Typography */
    --font-family: 'Poppins', sans-serif;
    --font-size-base: 16px;
    --line-height-base: 1.5;
    
    /* Spacing */
    --spacing-xs: 0.25rem;
    --spacing-sm: 0.5rem;
    --spacing-md: 1rem;
    --spacing-lg: 1.5rem;
    --spacing-xl: 2rem;
    
    /* Border Radius */
    --border-radius-sm: 4px;
    --border-radius-md: 8px;
    --border-radius-lg: 16px;
    --border-radius-xl: 24px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;
    
    /* Water Progress Colors */
    --progress-low: var(--danger-color);
    --progress-medium: var(--warning-color);
    --progress-high: var(--success-color);
}

/* Dark Theme Variables */
.dark-theme {
    --background-color: #121212;
    --card-color: #1e1e1e;
    --text-color: #f0f0f0;
    --text-secondary: #b0b0b0;
    --border-color: #333333;
    --shadow-color: rgba(0, 0, 0, 0.3);
}

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

html {
    font-size: var(--font-size-base);
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    line-height: var(--line-height-base);
    color: var(--text-color);
    background-color: var(--background-color);
    transition: background-color var(--transition-normal), color var(--transition-normal);
    padding: var(--spacing-md);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
    margin-bottom: var(--spacing-md);
    line-height: 1.2;
}

h1 {
    font-size: 2.5rem;
    color: var(--primary-color);
}

h2 {
    font-size: 1.75rem;
    color: var(--text-color);
    border-bottom: 2px solid var(--primary-color);
    padding-bottom: var(--spacing-xs);
    display: inline-block;
}

p {
    margin-bottom: var(--spacing-md);
}

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

a:hover {
    color: var(--accent-color);
    text-decoration: underline;
}

/* Layout */
header {
    text-align: center;
    margin-bottom: var(--spacing-xl);
    padding: var(--spacing-lg) 0;
}

.tagline {
    color: var(--text-secondary);
    font-size: 1.1rem;
    margin-top: var(--spacing-xs);
}

main {
    max-width: 800px;
    margin: 0 auto;
    flex: 1;
}

section {
    background-color: var(--card-color);
    border-radius: var(--border-radius-lg);
    padding: var(--spacing-lg);
    margin-bottom: var(--spacing-xl);
    box-shadow: 0 4px 12px var(--shadow-color);
    transition: background-color var(--transition-normal), box-shadow var(--transition-normal);
}

footer {
    text-align: center;
    padding: var(--spacing-lg) 0;
    margin-top: var(--spacing-xl);
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Theme Toggle */
.theme-toggle {
    position: fixed;
    top: var(--spacing-md);
    right: var(--spacing-md);
    z-index: 100;
}

#themeToggle {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    cursor: pointer;
    padding: var(--spacing-xs);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: background-color var(--transition-fast);
}

#themeToggle:hover {
    background-color: rgba(0, 0, 0, 0.1);
}

.dark-theme #themeToggle:hover {
    background-color: rgba(255, 255, 255, 0.1);
}

.icon-light, .icon-dark {
    display: block;
    transition: transform var(--transition-normal), opacity var(--transition-normal);
}

.dark-theme .icon-light {
    transform: translateY(-20px);
    opacity: 0;
    position: absolute;
}

.light-theme .icon-dark {
    transform: translateY(20px);
    opacity: 0;
    position: absolute;
}

/* Buttons */
button {
    cursor: pointer;
    font-family: var(--font-family);
    font-weight: 500;
    transition: all var(--transition-fast);
    border: none;
    border-radius: var(--border-radius-md);
    padding: var(--spacing-sm) var(--spacing-md);
    outline: none;
}

button:focus {
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.3);
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
    padding: var(--spacing-sm) var(--spacing-lg);
}

.primary-btn:hover {
    background-color: #1976D2;
    transform: translateY(-2px);
}

.primary-btn:active {
    transform: translateY(0);
}

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

.secondary-btn:hover {
    background-color: rgba(0, 0, 0, 0.05);
    border-color: var(--text-secondary);
}

.dark-theme .secondary-btn:hover {
    background-color: rgba(255, 255, 255, 0.05);
}

.water-btn {
    background-color: var(--primary-color);
    color: white;
    padding: var(--spacing-md) var(--spacing-md);
    border-radius: var(--border-radius-md);
    font-size: 1rem;
    transition: all var(--transition-fast);
    flex: 1;
    min-width: 80px;
    margin: 0 var(--spacing-xs);
}

.water-btn:hover {
    background-color: #1976D2;
    transform: translateY(-2px);
}

.water-btn:active {
    transform: translateY(0);
}

/* Forms and Inputs */
input {
    font-family: var(--font-family);
    font-size: 1rem;
    padding: var(--spacing-sm) var(--spacing-md);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius-md);
    background-color: var(--card-color);
    color: var(--text-color);
    transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
    width: 100%;
}

input:focus {
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(33, 150, 243, 0.2);
    outline: none;
}

.goal-input-container, .custom-input-container {
    position: relative;
    display: flex;
    align-items: center;
}

.unit {
    position: absolute;
    right: var(--spacing-md);
    color: var(--text-secondary);
    pointer-events: none;
}

input[type="number"] {
    -moz-appearance: textfield;
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
    -webkit-appearance: none;
    margin: 0;
}

/* Goal Section */
.goal-container {
    display: flex;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-md);
}

.goal-input-container {
    flex: 1;
}

.current-goal {
    font-weight: 500;
    color: var(--primary-color);
}

/* Progress Section */
.progress-container {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: var(--spacing-lg);
}

.progress-visual {
    position: relative;
    width: 200px;
    height: 200px;
    display: flex;
    justify-content: center;
    align-items: center;
}

.water-container {
    position: absolute;
    width: 160px;
    height: 160px;
    border-radius: 50%;
    overflow: hidden;
    background-color: rgba(33, 150, 243, 0.1);
    border: 4px solid var(--primary-color);
}

.water-level {
    position: absolute;
    bottom: 0;
    width: 100%;
    background-color: var(--primary-color);
    transition: height var(--transition-slow), background-color var(--transition-normal);
    height: 0%;
}

.progress-percentage {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-color);
    z-index: 2;
}

.progress-stats {
    display: flex;
    justify-content: space-around;
    width: 100%;
    margin-top: var(--spacing-md);
}

.stat {
    text-align: center;
    padding: var(--spacing-md);
    background-color: rgba(33, 150, 243, 0.1);
    border-radius: var(--border-radius-md);
    min-width: 150px;
}

.stat-label {
    display: block;
    color: var(--text-secondary);
    margin-bottom: var(--spacing-xs);
}

.stat-value {
    font-size: 1.2rem;
    font-weight: 600;
    color: var(--primary-color);
}

.congrats-message {
    margin-top: var(--spacing-lg);
    padding: var(--spacing-md);
    background-color: rgba(76, 175, 80, 0.1);
    border-left: 4px solid var(--success-color);
    border-radius: var(--border-radius-md);
    text-align: center;
    animation: fadeIn 0.5s ease;
}

.congrats-message p {
    margin: 0;
    color: var(--success-color);
    font-weight: 500;
}

/* Add Water Section */
.quick-add {
    display: flex;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: var(--spacing-md);
    margin-bottom: var(--spacing-lg);
}

.custom-add {
    display: flex;
    gap: var(--spacing-md);
    align-items: center;
}

.custom-input-container {
    flex: 1;
}

/* History Section */
.history-list {
    list-style-type: none;
    margin-bottom: var(--spacing-lg);
    max-height: 200px;
    overflow-y: auto;
}

.history-item {
    display: flex;
    justify-content: space-between;
    padding: var(--spacing-sm) 0;
    border-bottom: 1px solid var(--border-color);
}

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

.history-time {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.history-amount {
    font-weight: 500;
}

.history-actions {
    display: flex;
    justify-content: center;
}

/* Notification */
.notification {
    position: fixed;
    bottom: var(--spacing-lg);
    left: 50%;
    transform: translateX(-50%);
    background-color: var(--card-color);
    border-left: 4px solid var(--primary-color);
    border-radius: var(--border-radius-md);
    padding: var(--spacing-md) var(--spacing-lg);
    box-shadow: 0 4px 12px var(--shadow-color);
    display: flex;
    align-items: center;
    justify-content: space-between;
    min-width: 300px;
    max-width: 80%;
    z-index: 1000;
    animation: slideUp 0.3s ease;
}

.notification p {
    margin: 0;
    padding-right: var(--spacing-lg);
}

#closeNotification {
    background: transparent;
    border: none;
    font-size: 1.5rem;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 0;
}

/* Utility Classes */
.hidden {
    display: none;
}

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

@keyframes slideUp {
    from {
        transform: translate(-50%, 100%);
        opacity: 0;
    }
    to {
        transform: translate(-50%, 0);
        opacity: 1;
    }
}

@keyframes wave {
    0% {
        transform: translateX(-100%) translateZ(0) scaleY(1);
    }
    50% {
        transform: translateX(-30%) translateZ(0) scaleY(0.8);
    }
    100% {
        transform: translateX(0) translateZ(0) scaleY(1);
    }
}

/* Water animation */
.water-level::before {
    content: '';
    position: absolute;
    top: -10px;
    left: 0;
    width: 200%;
    height: 20px;
    background: rgba(255, 255, 255, 0.3);
    border-radius: 40%;
    animation: wave 3s infinite linear;
}

/* Media Queries */
@media (max-width: 768px) {
    :root {
        --font-size-base: 14px;
    }
    
    h1 {
        font-size: 2rem;
    }
    
    h2 {
        font-size: 1.5rem;
    }
    
    .goal-container {
        flex-direction: column;
    }
    
    .progress-container {
        gap: var(--spacing-md);
    }
    
    .progress-visual {
        width: 150px;
        height: 150px;
    }
    
    .water-container {
        width: 120px;
        height: 120px;
    }
    
    .progress-percentage {
        font-size: 1.5rem;
    }
    
    .progress-stats {
        flex-direction: column;
        gap: var(--spacing-md);
    }
    
    .stat {
        width: 100%;
    }
    
    .quick-add {
        flex-wrap: wrap;
    }
    
    .water-btn {
        flex: 1 0 40%;
        margin-bottom: var(--spacing-sm);
    }
    
    .custom-add {
        flex-direction: column;
    }
    
    .custom-input-container {
        width: 100%;
        margin-bottom: var(--spacing-sm);
    }
    
    #addCustomBtn {
        width: 100%;
    }
}

@media (max-width: 480px) {
    body {
        padding: var(--spacing-sm);
    }
    
    section {
        padding: var(--spacing-md);
    }
    
    .water-btn {
        flex: 1 0 100%;
    }
}