/* 
   CSS RESET & BASE STYLES
   */
* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* 
   CSS VARIABLES (Custom Properties)
   For easy theme management
   */
:root {
    /* Color Palette */
    --bg-color: rgba(0, 0, 0, 0.937);
    --bg-button-color: #1a1a1a;
    --bg-task-color: #2a2a2a;
    --bg-column-color: #1e1e1e;
    
    /* Action Button Colors */
    --delete-btn-color: #ff4d4d;        /* Red for delete actions */
    --move-btn-color: #4a9eff;          /* Blue for move to progress */
    --complete-btn-color: #4caf50;      /* Green for complete actions */
    --add-btn-color: #9c27b0;           /* Purple for add actions */
    
    /* Text Colors */
    --primary-text-color: #f4f4f4f1;
    --secondary-text-color: #aaaaaa;
    --placeholder-color: #888888;
    
    /* Hover States */
    --delete-btn-hover: #ff6666;
    --move-btn-hover: #6bb2ff;
    --complete-btn-hover: #66bb6a;
    --add-btn-hover: #b23fd4;
    
    /* Status Colors */
    --todo-color: #ff9800;     /* Orange for To Do */
    --progress-color: #2196f3;  /* Blue for In Progress */
    --done-color: #4caf50;      /* Green for Completed */
    
    /* Spacing Variables */
    --nav-padding: 15px 30px;
    --section-padding: 15px 30px;
    --padding-small: 5px;
    --padding-medium: 10px;
    --padding-large: 15px;
    --padding-Xlarge: 20px;
    --padding-XXlarge: 30px;
    
    /* Border Radius */
    --border-radius-small: 5px;
    --border-radius-medium: 10px;
    --border-radius-large: 15px;
    --border-radius-Xlarge: 20px;
    
    /* Transitions */
    --transition-fast: 0.2s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s cubic-bezier(0.19, 1, 0.22, 1);
}

/* 
   BASE HTML & BODY STYLES
   */
html, body {
    height: 100%;
    width: 100%;
    font-family: system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', 
                 Roboto, Oxygen, Ubuntu, Cantarell, 'Open Sans', 
                 'Helvetica Neue', sans-serif;
}

body {
    background-color: var(--bg-color);
    color: var(--primary-text-color);
    display: flex;
    flex-direction: column;
    min-height: 100vh;
}

/* 
   MAIN CONTENT AREA
   */
main {
    flex: 1 0 auto;
    display: flex;
    flex-direction: column;
}

/* 
   NAVIGATION BAR
   */
nav {
    padding: var(--nav-padding);
    display: flex;
    align-items: center;
    justify-content: space-between;
    position: sticky;
    top: 0;
    background-color: var(--bg-color);
    z-index: 100;
    border-bottom: 1px solid rgba(255, 255, 255, 0.1);
}

nav .left h2 {
    color: var(--move-btn-color);
    font-size: 1.8rem;
    font-weight: 700;
    letter-spacing: 1px;
}

nav button {
    background-color: var(--add-btn-color);
    cursor: pointer;
    border: none;
    outline: none;
    color: var(--primary-text-color);
    padding: var(--padding-medium) var(--padding-large);
    border-radius: var(--border-radius-medium);
    font-weight: 600;
    transition: all var(--transition-fast);
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.3);
}

nav button:hover {
    background-color: var(--add-btn-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.4);
}

nav button:active {
    transform: translateY(0);
}

/* 
   TASK BOARD SECTION
   */
section.board {
    padding: var(--section-padding);
    display: flex;
    flex-grow: 1;
    justify-content: space-between;
    gap: var(--padding-XXlarge);
    overflow-x: auto;
}

/* 
   TASK COLUMNS
   */
.task-column {
    background-color: var(--bg-column-color);
    flex-grow: 1;
    min-width: 300px;
    display: flex;
    flex-direction: column;
    gap: var(--padding-medium);
    border-radius: var(--border-radius-large);
    padding: var(--padding-large);
    box-shadow: 0 4px 6px rgba(0, 0, 0, 0.2);
    transition: all var(--transition-normal);
}

/* Column-specific colors */
#todo {
    border-top: 4px solid var(--todo-color);
}

#progress {
    border-top: 4px solid var(--progress-color);
}

#done {
    border-top: 4px solid var(--done-color);
}

/* Drag and Drop hover effect */
.task-column.hover-over {
    border: 2px dashed var(--primary-text-color);
    scale: 1.02;
    transition: all var(--transition-slow);
    background-color: rgba(255, 255, 255, 0.05);
}

/* 
   COLUMN HEADINGS
   */
.task-column .heading {
    width: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: var(--padding-small) 0;
    border-bottom: 2px solid rgba(255, 255, 255, 0.1);
    margin-bottom: var(--padding-medium);
}

.task-column .heading .left h3 {
    font-size: 1.3rem;
    font-weight: 600;
}

/* Column title colors */
#todo .heading .left h3 {
    color: var(--todo-color);
}

#progress .heading .left h3 {
    color: var(--progress-color);
}

#done .heading .left h3 {
    color: var(--done-color);
}

.task-column .heading .right {
    background-color: rgba(255, 255, 255, 0.1);
    padding: var(--padding-small) var(--padding-medium);
    border-radius: var(--border-radius-small);
    font-weight: 600;
    min-width: 40px;
    text-align: center;
}

/* 
   INDIVIDUAL TASK CARDS
   */
.task {
    background-color: var(--bg-task-color);
    padding: var(--padding-large);
    border-radius: var(--border-radius-medium);
    display: flex;
    flex-direction: column;
    gap: var(--padding-medium);
    cursor: grab;
    transition: all var(--transition-normal);
    border-left: 4px solid transparent;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.2);
}

.task:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
}

.task:active {
    cursor: grabbing;
}

/* Column-specific task borders */
#todo .task {
    border-left-color: var(--todo-color);
}

#progress .task {
    border-left-color: var(--progress-color);
}

#done .task {
    border-left-color: var(--done-color);
}

.task h2 {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--primary-text-color);
    margin-bottom: var(--padding-small);
}

.task p {
    font-size: 0.95rem;
    color: var(--secondary-text-color);
    line-height: 1.5;
    flex-grow: 1;
}

/* 
   TASK BUTTONS CONTAINER
   */
.task .button-container {
    display: flex;
    gap: var(--padding-small);
    margin-top: var(--padding-medium);
    flex-wrap: wrap;
}

/* 
   BUTTON BASE STYLES
   */
.task button {
    cursor: pointer;
    padding: var(--padding-small) var(--padding-medium);
    border-radius: var(--border-radius-small);
    border: none;
    font-weight: 500;
    font-size: 0.85rem;
    transition: all var(--transition-fast);
    flex: 1;
    min-width: 120px;
    text-align: center;
}

/* DELETE BUTTON */
.delete-btn {
    background-color: var(--delete-btn-color);
    color: white;
}

.delete-btn:hover {
    background-color: var(--delete-btn-hover);
    transform: translateY(-1px);
}

/* MOVE TO PROGRESS BUTTON */
.move-btn {
    background-color: var(--move-btn-color);
    color: white;
}

.move-btn:hover {
    background-color: var(--move-btn-hover);
    transform: translateY(-1px);
}

/* COMPLETE BUTTON */
.complete-btn {
    background-color: var(--complete-btn-color);
    color: white;
}

.complete-btn:hover {
    background-color: var(--complete-btn-hover);
    transform: translateY(-1px);
}

/* 
   MODAL STYLES
   */
.modal {
    position: fixed;
    height: 100vh;
    width: 100vw;
    top: 0;
    left: 0;
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal.active {
    display: flex;
}

.modal .bg {
    position: absolute;
    height: 100%;
    width: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(5px);
    animation: fadeIn 0.3s ease;
}

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

.modal .center {
    background-color: var(--bg-button-color);
    padding: var(--padding-XXlarge);
    border-radius: var(--border-radius-large);
    display: flex;
    flex-direction: column;
    gap: var(--padding-large);
    z-index: 1010;
    width: 90%;
    max-width: 500px;
    animation: slideUp 0.4s cubic-bezier(0.175, 0.885, 0.32, 1.275);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
}

@keyframes slideUp {
    from {
        opacity: 0;
        transform: translateY(50px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.modal .center input,
.modal .center textarea {
    background-color: var(--bg-task-color);
    border: 1px solid rgba(255, 255, 255, 0.1);
    outline: none;
    color: var(--primary-text-color);
    padding: var(--padding-large);
    border-radius: var(--border-radius-medium);
    font-size: 1rem;
    transition: border-color var(--transition-fast);
}

.modal .center input:focus,
.modal .center textarea:focus {
    border-color: var(--move-btn-color);
}

.modal .center input::placeholder,
.modal .center textarea::placeholder {
    color: var(--placeholder-color);
}

.modal .center textarea {
    min-height: 120px;
    resize: vertical;
    font-family: inherit;
}

.modal .center .add-task-btn {
    background-color: var(--add-btn-color);
    border: none;
    outline: none;
    color: var(--primary-text-color);
    padding: var(--padding-large) var(--padding-Xlarge);
    cursor: pointer;
    border-radius: var(--border-radius-medium);
    font-weight: 600;
    font-size: 1rem;
    transition: all var(--transition-fast);
    align-self: stretch;
}

.modal .center .add-task-btn:hover {
    background-color: var(--add-btn-hover);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(0, 0, 0, 0.3);
}

/* 
   FOOTER STYLES
   */
footer {
    background-color: var(--bg-button-color);
    color: var(--primary-text-color);
    text-align: center;
    padding: 1.5rem 0;
    font-size: 0.9rem;
    border-top: 1px solid rgba(255, 255, 255, 0.1);
    margin-top: auto;
    line-height: 1.5;
    width: 100%;
    flex-shrink: 0;
}

footer a {
    color: var(--move-btn-color);
    text-decoration: none;
    font-weight: 500;
    transition: color var(--transition-fast);
}

footer a:hover {
    color: var(--move-btn-hover);
    text-decoration: underline;
}

/* 
   RESPONSIVE DESIGN
   */

/* Tablets and small laptops */
@media (max-width: 1024px) {
    section.board {
        gap: var(--padding-large);
    }
    
    .task-column {
        min-width: 250px;
    }
}

/* Mobile devices */
@media (max-width: 768px) {
    nav {
        flex-direction: column;
        gap: var(--padding-medium);
        text-align: center;
        padding: var(--padding-large);
    }
    
    nav button {
        width: 100%;
        margin-top: var(--padding-small);
    }
    
    section.board {
        flex-direction: column;
        gap: var(--padding-large);
        padding: var(--padding-large);
        overflow-x: visible;
    }
    
    .task-column {
        width: 100%;
        min-width: unset;
    }
    
    .task-column.hover-over {
        scale: 1.01;
    }
    
    .modal .center {
        width: 95%;
        padding: var(--padding-large);
    }
    
    .task button {
        min-width: 100px;
        font-size: 0.8rem;
    }
}

/* Small phones */
@media (max-width: 480px) {
    nav {
        padding: var(--padding-medium);
    }
    
    nav .left h2 {
        font-size: 1.5rem;
    }
    
    section.board {
        padding: var(--padding-medium);
    }
    
    .task-column {
        padding: var(--padding-medium);
    }
    
    .task {
        padding: var(--padding-medium);
    }
    
    .task .button-container {
        flex-direction: column;
    }
    
    .task button {
        width: 100%;
        min-width: unset;
    }
    
    .modal .center {
        padding: var(--padding-medium);
        gap: var(--padding-medium);
    }
    
    footer {
        padding: 1rem 0;
        font-size: 0.8rem;
    }
}

/* 
   UTILITY CLASSES (Optional)
   */
.empty-state {
    text-align: center;
    padding: var(--padding-Xlarge);
    color: var(--secondary-text-color);
    font-style: italic;
}

.empty-state::before {
    content: "📋";
    display: block;
    font-size: 2rem;
    margin-bottom: var(--padding-medium);
}

/* Animation for task addition */
@keyframes taskAdd {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.task {
    animation: taskAdd 0.3s ease;
}