/* ========================================
   TO-DO LIST — Modern CSS
   ======================================== */

/* --- CSS Custom Properties --- */
:root {
    --clr-primary: #667eea;
    --clr-primary-dark: #5a67d8;
    --clr-accent: #764ba2;
    --clr-danger: #f56565;
    --clr-danger-dark: #e53e3e;
    --clr-text: #2d3748;
    --clr-text-light: #4a5568;
    --clr-text-muted: #a0aec0;
    --clr-bg-card: rgba(255, 255, 255, 0.95);
    --clr-bg-input: #f7fafc;
    --clr-border: #e2e8f0;
    --clr-scrollbar-track: #f1f5f9;
    --clr-scrollbar-thumb: #cbd5e0;
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 20px;
    --shadow-card: 0 20px 40px rgba(0, 0, 0, 0.1);
    --shadow-btn: 0 4px 15px rgba(102, 126, 234, 0.3);
    --transition: 0.3s ease;
    --font-family: 'Inter', 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
}

/* --- Reset --- */
*,
*::before,
*::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

/* --- Body --- */
body {
    font-family: var(--font-family);
    background: linear-gradient(135deg, var(--clr-primary) 0%, var(--clr-accent) 100%);
    min-height: 100vh;
    min-height: 100dvh;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    padding: 40px 20px;
}

/* --- Main Layout --- */
.todo {
    width: 100%;
    max-width: 1000px;
    display: flex;
    gap: 24px;
    align-items: flex-start;
}

/* --- Shared Card Styles --- */
.container,
.history-container {
    background: var(--clr-bg-card);
    backdrop-filter: blur(12px);
    border-radius: var(--radius-lg);
    padding: 32px;
    box-shadow: var(--shadow-card);
    border: 1px solid rgba(255, 255, 255, 0.25);
}

.container {
    flex: 1.2;
    min-width: 0;
}

.history-container {
    flex: 0.8;
    min-width: 0;
}

/* --- Header --- */
header {
    text-align: center;
    margin-bottom: 28px;
}

h1 {
    font-size: 2.2rem;
    font-weight: 800;
    background: linear-gradient(135deg, var(--clr-primary), var(--clr-accent));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1.2;
}

.subtitle {
    color: var(--clr-text-muted);
    font-size: 0.9rem;
    font-weight: 500;
    margin-top: 6px;
}

/* --- Input Group --- */
.input-group {
    display: flex;
    gap: 10px;
    margin-bottom: 16px;
}

#task-input {
    flex: 1;
    padding: 14px 20px;
    border: 2px solid var(--clr-border);
    border-radius: var(--radius-md);
    font-size: 15px;
    font-weight: 500;
    font-family: var(--font-family);
    color: var(--clr-text);
    background: var(--clr-bg-input);
    transition: all var(--transition);
    min-width: 0;
}

#task-input:focus {
    outline: none;
    border-color: var(--clr-primary);
    background: white;
    box-shadow: 0 0 0 3px rgba(102, 126, 234, 0.15);
}

#task-input::placeholder {
    color: var(--clr-text-muted);
}

#task-input.shake {
    animation: shake 0.4s ease;
    border-color: var(--clr-danger);
}

@keyframes shake {
    0%, 100% { transform: translateX(0); }
    20% { transform: translateX(-6px); }
    40% { transform: translateX(6px); }
    60% { transform: translateX(-4px); }
    80% { transform: translateX(4px); }
}

#add-task-btn {
    padding: 14px 22px;
    background: linear-gradient(135deg, var(--clr-primary), var(--clr-accent));
    color: white;
    border: none;
    border-radius: var(--radius-md);
    font-size: 15px;
    font-weight: 600;
    font-family: var(--font-family);
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: var(--shadow-btn);
    display: flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
}

#add-task-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 8px 25px rgba(102, 126, 234, 0.4);
}

#add-task-btn:active {
    transform: translateY(0);
}

#add-task-btn:focus-visible {
    outline: 3px solid var(--clr-primary);
    outline-offset: 2px;
}

/* --- Task Count --- */
.task-count {
    font-size: 13px;
    font-weight: 600;
    color: var(--clr-text-muted);
    margin-bottom: 12px;
    padding: 0 4px;
}

/* --- Task List --- */
.ulist {
    max-height: 420px;
    overflow-y: auto;
    padding-right: 6px;
}

.ulist::-webkit-scrollbar { width: 5px; }
.ulist::-webkit-scrollbar-track { background: var(--clr-scrollbar-track); border-radius: 3px; }
.ulist::-webkit-scrollbar-thumb { background: var(--clr-scrollbar-thumb); border-radius: 3px; }
.ulist::-webkit-scrollbar-thumb:hover { background: var(--clr-text-muted); }

ul {
    list-style: none;
    padding: 0;
}

li {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 14px 18px;
    margin-bottom: 8px;
    background: white;
    border-radius: var(--radius-md);
    box-shadow: 0 2px 8px rgba(0, 0, 0, 0.04);
    border: 1px solid var(--clr-border);
    transition: all var(--transition);
    animation: slideIn 0.3s ease;
}

li:hover {
    transform: translateY(-2px);
    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.08);
}

@keyframes slideIn {
    from { opacity: 0; transform: translateY(14px); }
    to   { opacity: 1; transform: translateY(0); }
}

li span {
    flex: 1;
    font-size: 15px;
    font-weight: 500;
    color: var(--clr-text);
    cursor: pointer;
    transition: color var(--transition);
    padding: 4px 0;
    word-break: break-word;
}

li span:hover {
    color: var(--clr-primary);
}

.task-completed {
    text-decoration: line-through;
    color: var(--clr-text-muted) !important;
    font-style: italic;
}

/* --- Delete Button --- */
.delete-btn {
    padding: 7px 14px;
    background: linear-gradient(135deg, var(--clr-danger), var(--clr-danger-dark));
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 13px;
    font-weight: 600;
    font-family: var(--font-family);
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: 0 2px 8px rgba(245, 101, 101, 0.25);
    margin-left: 12px;
    flex-shrink: 0;
}

.delete-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(245, 101, 101, 0.4);
    background: linear-gradient(135deg, var(--clr-danger-dark), #c53030);
}

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

.delete-btn:focus-visible {
    outline: 3px solid var(--clr-danger);
    outline-offset: 2px;
}

/* --- Empty State --- */
.empty-state,
.empty-history {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 32px 16px;
    color: var(--clr-text-muted);
    text-align: center;
}

.empty-state svg {
    margin-bottom: 12px;
    opacity: 0.35;
    stroke: var(--clr-text-muted);
}

.empty-state p,
.empty-history p {
    font-size: 14px;
    font-weight: 500;
}

.empty-state.hidden,
.empty-history.hidden {
    display: none;
}

hr {
    display: none;
}

/* --- History Section --- */
.history-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 18px;
}

.history-header h2 {
    color: var(--clr-text);
    font-size: 1.3rem;
    font-weight: 700;
    margin: 0;
}

#clear-history-btn {
    padding: 7px 14px;
    background: linear-gradient(135deg, var(--clr-danger), var(--clr-danger-dark));
    color: white;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 12px;
    font-weight: 600;
    font-family: var(--font-family);
    cursor: pointer;
    transition: all var(--transition);
    box-shadow: 0 2px 8px rgba(245, 101, 101, 0.25);
}

#clear-history-btn:hover {
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(245, 101, 101, 0.4);
    background: linear-gradient(135deg, var(--clr-danger-dark), #c53030);
}

#clear-history-btn:focus-visible {
    outline: 3px solid var(--clr-danger);
    outline-offset: 2px;
}

.history-list {
    max-height: 400px;
    overflow-y: auto;
    padding-right: 6px;
}

.history-list::-webkit-scrollbar { width: 5px; }
.history-list::-webkit-scrollbar-track { background: var(--clr-scrollbar-track); border-radius: 3px; }
.history-list::-webkit-scrollbar-thumb { background: var(--clr-scrollbar-thumb); border-radius: 3px; }
.history-list::-webkit-scrollbar-thumb:hover { background: var(--clr-text-muted); }

.history-item {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 10px 14px;
    margin-bottom: 6px;
    background: var(--clr-bg-input);
    border-radius: var(--radius-sm);
    border: 1px solid var(--clr-border);
    transition: all var(--transition);
    animation: slideIn 0.3s ease;
}

.history-task {
    flex: 1;
    font-size: 13px;
    font-weight: 500;
    color: var(--clr-text-light);
    text-decoration: line-through;
    font-style: italic;
    word-break: break-word;
}

.timestamp {
    font-size: 11px;
    color: var(--clr-text-muted);
    font-weight: 400;
    margin-left: 10px;
    flex-shrink: 0;
    white-space: nowrap;
}

/* --- Footer --- */
.app-footer {
    margin-top: auto;
    padding-top: 40px;
    text-align: center;
    color: rgba(255, 255, 255, 0.8);
    font-size: 14px;
    font-weight: 500;
}

.app-footer a {
    color: white;
    text-decoration: none;
    font-weight: 600;
    transition: color var(--transition);
}

.app-footer a:hover {
    color: var(--clr-accent);
}

/* ========================================
   RESPONSIVE DESIGN
   ======================================== */

/* Tablet landscape & smaller desktops */
@media (max-width: 900px) {
    .todo {
        flex-direction: column;
        gap: 20px;
    }

    .container,
    .history-container {
        flex: none;
        width: 100%;
    }
}

/* Tablet portrait */
@media (max-width: 768px) {
    body {
        padding: 24px 16px;
    }

    .container,
    .history-container {
        padding: 24px;
        border-radius: 16px;
    }

    h1 {
        font-size: 1.9rem;
    }
}

/* Large phones */
@media (max-width: 600px) {
    body {
        padding: 16px 10px;
    }

    .container,
    .history-container {
        padding: 20px 16px;
        border-radius: 14px;
    }

    h1 {
        font-size: 1.7rem;
    }

    .subtitle {
        font-size: 0.82rem;
    }

    .input-group {
        flex-direction: column;
    }

    #add-task-btn {
        width: 100%;
        justify-content: center;
    }

    li {
        padding: 12px 14px;
    }

    li span {
        font-size: 14px;
    }

    .delete-btn {
        padding: 6px 12px;
        font-size: 12px;
    }

    .history-header {
        flex-direction: column;
        gap: 10px;
        align-items: flex-start;
    }

    .history-header h2 {
        font-size: 1.15rem;
    }
}

/* Small phones */
@media (max-width: 400px) {
    body {
        padding: 10px 6px;
    }

    .container,
    .history-container {
        padding: 16px 12px;
        border-radius: 12px;
    }

    h1 {
        font-size: 1.45rem;
    }

    .subtitle {
        font-size: 0.78rem;
    }

    header {
        margin-bottom: 20px;
    }

    #task-input {
        padding: 12px 14px;
        font-size: 14px;
    }

    #add-task-btn {
        padding: 12px 16px;
        font-size: 14px;
    }

    li {
        padding: 10px 12px;
        margin-bottom: 6px;
    }

    li span {
        font-size: 13px;
    }

    .delete-btn {
        padding: 5px 10px;
        font-size: 11px;
        margin-left: 8px;
    }

    .ulist,
    .history-list {
        max-height: 320px;
    }

    .task-count {
        font-size: 12px;
    }
}

/* Very small devices / foldables */
@media (max-width: 340px) {
    h1 {
        font-size: 1.25rem;
    }

    .container,
    .history-container {
        padding: 14px 10px;
    }
}