/* ====== Base / Layout ====== */
:root {
      --bg: #0f172a;
      --bg-elevated: #111827;
      --bg-elevated-2: #020617;
      --accent: #22c55e;
      --accent-soft: rgba(34, 197, 94, 0.16);
      --text: #e5e7eb;
      --text-muted: #9ca3af;
      --border-subtle: #1f2937;
      --danger: #ef4444;
      --radius-lg: 12px;
      --radius-md: 8px;
      --shadow-soft: 0 14px 40px rgba(0, 0, 0, 0.65);
      --shadow-soft-sm: 0 10px 30px rgba(0, 0, 0, 0.6);
    }

    * {
      box-sizing: border-box;
      margin: 0;
      padding: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
    }

    body {
      min-height: 100vh;
      background: radial-gradient(circle at top, #1f2937 0, #020617 40%, #000 100%);
      color: var(--text);
      display: flex;
      justify-content: center;
      padding: 32px 16px;
    }
    .app {
        width: 100%;
        max-width: 1100px;
        background: linear-gradient(145deg, rgba(15, 23, 42, 0.96), rgba(15, 23, 42, 0.99));
        border-radius: 20px;
        border: 1px solid rgba(148, 163, 184, 0.12);
        box-shadow: var(--shadow-soft);
        padding: 24px 22px 26px;
        backdrop-filter: blur(20px);
      }
  
      @media (min-width: 768px) {
        .app {
          padding: 26px 28px 28px;
        }
      }
  
      /* ====== Header ====== */
      .header {
        display: flex;
        flex-wrap: wrap;
        justify-content: space-between;
        gap: 10px;
        align-items: baseline;
        margin-bottom: 20px;
      }
      .title-group h1 {
        font-size: 1.75rem;
        letter-spacing: 0.04em;
        display: flex;
        align-items: center;
        gap: 8px;
      }
  
      .title-accent-dot {
        width: 9px;
        height: 9px;
        border-radius: 999px;
        background: radial-gradient(circle at 30% 30%, #bbf7d0 0, #22c55e 40%, #14532d 100%);
        box-shadow: 0 0 16px rgba(34, 197, 94, 0.9);
      }
  
      .title-group p {
        font-size: 0.85rem;
        color: var(--text-muted);
        margin-top: 4px;
      }
      .title-group h1 {
        font-size: 1.75rem;
        letter-spacing: 0.04em;
        display: flex;
        align-items: center;
        gap: 8px;
      }
  
      .title-accent-dot {
        width: 9px;
        height: 9px;
        border-radius: 999px;
        background: radial-gradient(circle at 30% 30%, #bbf7d0 0, #22c55e 40%, #14532d 100%);
        box-shadow: 0 0 16px rgba(34, 197, 94, 0.9);
      }
  
      .title-group p {
        font-size: 0.85rem;
        color: var(--text-muted);
        margin-top: 4px;
      }
      .card-header {
        display: flex;
        justify-content: space-between;
        align-items: baseline;
        margin-bottom: 14px;
      }
  
      .card-header h2 {
        font-size: 1rem;
        letter-spacing: 0.05em;
        text-transform: uppercase;
        color: #e5e7eb;
      }
  
      .card-header small {
        font-size: 0.8rem;
        color: var(--text-muted);
      }
  
      .form-grid {
        display: grid;
        grid-template-columns: repeat(12, minmax(0, 1fr));
        gap: 10px 12px;
        align-items: flex-end;
      }
      .form-group {
        display: flex;
        flex-direction: column;
        gap: 6px;
      }
  
      .form-group label {
        font-size: 0.8rem;
        color: #d1d5db;
        text-transform: uppercase;
        letter-spacing: 0.08em;
      }
  
      .form-group input,
      .form-group select,
      .form-group textarea {
        background: rgba(15, 23, 42, 0.9);
        border-radius: var(--radius-md);
        border: 1px solid var(--border-subtle);
        color: var(--text);
        padding: 7px 9px;
        font-size: 0.9rem;
        outline: none;
        transition: border-color 0.16s ease, box-shadow 0.16s ease, background 0.16s ease, transform 0.06s ease;
      }
  
      .form-group input::placeholder,
      .form-group textarea::placeholder {
        color: rgba(148, 163, 184, 0.8);
      }
      .form-group input:focus,
    .form-group select:focus,
    .form-group textarea:focus {
      border-color: var(--accent);
      box-shadow: 0 0 0 1px rgba(34, 197, 94, 0.4);
      background: #020617;
      transform: translateY(-0.5px);
    }

    .form-group textarea {
      resize: vertical;
      min-height: 38px;
      max-height: 94px;
    }
    .btn-primary {
        border: none;
        border-radius: 999px;
        padding: 9px 16px;
        font-size: 0.9rem;
        text-transform: uppercase;
        letter-spacing: 0.11em;
        background: radial-gradient(circle at 30% 0, #4ade80 0, #16a34a 45%, #15803d 100%);
        color: #020617;
        font-weight: 600;
        cursor: pointer;
        display: inline-flex;
        align-items: center;
        justify-content: center;
        gap: 6px;
        box-shadow: 0 18px 45px rgba(22, 163, 74, 0.7);
        white-space: nowrap;
        transition: transform 0.1s ease, box-shadow 0.1s ease, filter 0.1s ease;
      }
  
      .btn-primary span.icon {
        font-size: 1rem;
        display: inline-block;
        transform: translateY(1px);
      }
  
      .btn-primary:hover {
        transform: translateY(-1px);
        box-shadow: 0 20px 55px rgba(22, 163, 74, 0.8);
        filter: brightness(1.02);
      }
      .btn-primary:active {
        transform: translateY(1px) scale(0.99);
        box-shadow: 0 10px 32px rgba(22, 163, 74, 0.7);
        filter: brightness(0.96);
      }
  
      .btn-secondary {
        border-radius: 999px;
        border: 1px solid rgba(148, 163, 184, 0.5);
        padding: 6px 12px;
        background: rgba(15, 23, 42, 0.85);
        color: var(--text-muted);
        font-size: 0.78rem;
        text-transform: uppercase;
        letter-spacing: 0.12em;
        cursor: pointer;
        transition: background 0.15s ease, color 0.15s ease, border-color 0.15s ease, transform 0.08s ease;
      }
  
      .btn-secondary:hover {
        background: rgba(15, 23, 42, 1);
        color: #e5e7eb;
        border-color: rgba(148, 163, 184, 0.9);
        transform: translateY(-0.5px);
      }
  
      .btn-secondary:active {
        transform: translateY(0.5px);
      }
      .small-actions {
        display: flex;
        gap: 8px;
        margin-top: 6px;
        justify-content: flex-end;
      }
  
      /* Responsive layout for form grid */
      @media (min-width: 992px) {
        .form-title   { grid-column: span 4; }
        .form-topic   { grid-column: span 3; }
        .form-diff    { grid-column: span 2; }
        .form-period  { grid-column: span 3; }
        .form-notes   { grid-column: span 8; }
        .form-submit  { grid-column: span 4; display: flex; justify-content: flex-end; }
      }
  
      @media (min-width: 640px) and (max-width: 991px) {
        .form-title   { grid-column: span 6; }
        .form-topic   { grid-column: span 6; }
        .form-diff    { grid-column: span 4; }
        .form-period  { grid-column: span 8; }
        .form-notes   { grid-column: span 12; }
        .form-submit  { grid-column: span 12; display: flex; justify-content: flex-end; }
      }
      @media (max-width: 639px) {
        .form-grid {
          grid-template-columns: repeat(1, minmax(0, 1fr));
        }
        .form-submit {
          display: flex;
          justify-content: flex-end;
        }
      }
  
      /* ====== Task Columns ====== */
      .columns-header {
        display: flex;
        justify-content: space-between;
        align-items: baseline;
        margin: 6px 4px 8px;
        gap: 10px;
      }
  
      .columns-header h2 {
        font-size: 0.9rem;
        text-transform: uppercase;
        letter-spacing: 0.12em;
        color: var(--text-muted);
      }
      .columns-header small {
        font-size: 0.8rem;
        color: var(--text-muted);
      }
  
      .columns {
        display: grid;
        grid-template-columns: repeat(3, minmax(0, 1fr));
        gap: 10px;
      }
  
      @media (max-width: 860px) {
        .columns {
          grid-template-columns: repeat(2, minmax(0, 1fr));
        }
      }
  
      @media (max-width: 640px) {
        .columns {
          grid-template-columns: minmax(0, 1fr);
        }
      }
  
      .column {
        background: var(--bg-elevated-2);
        border-radius: var(--radius-lg);
        border: 1px solid rgba(31, 41, 55, 0.8);
        padding: 12px 12px 10px;
        min-height: 80px;
        display: flex;
        flex-direction: column;
        gap: 8px;
        position: relative;
        overflow: hidden;
      }
      .column-title {
        font-size: 0.8rem;
        text-transform: uppercase;
        letter-spacing: 0.15em;
        color: var(--text-muted);
        margin-bottom: 2px;
        display: flex;
        justify-content: space-between;
        align-items: center;
      }
  
      .column-count {
        font-size: 0.7rem;
        color: rgba(148, 163, 184, 0.9);
        background: rgba(15, 23, 42, 0.9);
        border-radius: 999px;
        padding: 2px 7px;
        border: 1px solid rgba(55, 65, 81, 0.9);
      }
  
      .column::before {
        content: "";
        position: absolute;
        inset: -40%;
        opacity: 0;
        pointer-events: none;
        transition: opacity 0.2s ease;
      }
      .column--today::before {
        background: radial-gradient(circle at top center, rgba(34, 197, 94, 0.1), transparent 60%);
      }
  
      .column--week::before {
        background: radial-gradient(circle at top center, rgba(59, 130, 246, 0.1), transparent 60%);
      }
  
      .column--later::before {
        background: radial-gradient(circle at top center, rgba(244, 114, 182, 0.12), transparent 60%);
      }
  
      .column:hover::before {
        opacity: 1;
      }
  
      .empty-state {
        font-size: 0.8rem;
        color: rgba(148, 163, 184, 0.9);
        border-radius: var(--radius-md);
        padding: 8px 9px;
        background: rgba(15, 23, 42, 0.85);
        border: 1px dashed rgba(75, 85, 99, 0.8);
      }
      /* ====== Task Cards ====== */
    .task {
        display: flex;
        gap: 8px;
        padding: 8px 9px 7px;
        border-radius: var(--radius-md);
        background: rgba(15, 23, 42, 0.95);
        border: 1px solid rgba(55, 65, 81, 0.9);
        box-shadow: 0 10px 26px rgba(0, 0, 0, 0.8);
        align-items: flex-start;
        position: relative;
        overflow: hidden;
      }
  
      .task::after {
        content: "";
        position: absolute;
        inset: 0;
        pointer-events: none;
        border-radius: inherit;
        background: radial-gradient(circle at top left, rgba(34, 197, 94, 0.16), transparent 60%);
        opacity: 0;
        transition: opacity 0.18s ease;
      }
  
      .task:hover::after {
        opacity: 1;
      }
      .task-left {
        padding-top: 3px;
      }
  
      /* Custom checkbox */
      .checkbox-wrapper {
        position: relative;
        width: 18px;
        height: 18px;
      }
  
      .checkbox-wrapper input[type="checkbox"] {
        appearance: none;
        -webkit-appearance: none;
        position: absolute;
        inset: 0;
        margin: 0;
        cursor: pointer;
        border-radius: 6px;
        border: 1px solid rgba(75, 85, 99, 0.95);
        background: radial-gradient(circle at top, rgba(31, 41, 55, 0.95) 0, #020617 60%);
        box-shadow: 0 5px 14px rgba(0, 0, 0, 0.7);
        display: grid;
        place-items: center;
        outline: none;
        transition: border-color 0.16s ease, background 0.16s ease, transform 0.1s ease, box-shadow 0.1s ease;
      }
      .checkbox-wrapper input[type="checkbox"]::before {
        content: "✔";
        font-size: 0.72rem;
        color: #e5e7eb;
        transform: scale(0) translateY(1px);
        transition: transform 0.15s ease-out;
      }
  
      .checkbox-wrapper input[type="checkbox"]:checked {
        border-color: rgba(34, 197, 94, 0.95);
        background: radial-gradient(circle at 30% 0, rgba(74, 222, 128, 0.99) 0, #16a34a 45%, #166534 100%);
        box-shadow: 0 14px 30px rgba(21, 128, 61, 0.95);
        transform: translateY(1px);
      }
  
      .checkbox-wrapper input[type="checkbox"]:checked::before {
        transform: scale(1) translateY(1px);
      }
  
      .task-main {
        flex: 1;
        min-width: 0;
      }
  
      .task-title-row {
        display: flex;
        justify-content: space-between;
        gap: 8px;
        align-items: baseline;
        margin-bottom: 2px;
      }
      .task-title {
        font-size: 0.95rem;
        font-weight: 500;
        word-break: break-word;
      }
  
      .task-meta {
        display: flex;
        flex-wrap: wrap;
        gap: 4px;
        margin-bottom: 3px;
      }
  
      .pill {
        font-size: 0.7rem;
        text-transform: uppercase;
        letter-spacing: 0.12em;
        border-radius: 999px;
        padding: 1px 7px 2px;
        border: 1px solid rgba(75, 85, 99, 0.9);
        color: rgba(209, 213, 219, 0.9);
        background: rgba(15, 23, 42, 0.9);
      }
  
      .pill--easy {
        border-color: rgba(34, 197, 94, 0.9);
        color: #bbf7d0;
        background: rgba(22, 163, 74, 0.22);
      }
      .pill--medium {
        border-color: rgba(234, 179, 8, 0.9);
        color: #facc15;
        background: rgba(202, 138, 4, 0.22);
      }
  
      .pill--hard {
        border-color: rgba(248, 113, 113, 0.95);
        color: #fecaca;
        background: rgba(220, 38, 38, 0.28);
      }
  
      .pill--topic {
        border-style: dashed;
        color: rgba(191, 219, 254, 0.95);
        border-color: rgba(59, 130, 246, 0.9);
        background: rgba(15, 23, 42, 0.98);
      }
  
      .pill--platform {
        border-style: dashed;
        color: rgba(244, 244, 245, 0.9);
        border-color: rgba(148, 163, 184, 0.95);
        background: rgba(15, 23, 42, 0.96);
      }
  
      .task-notes {
        font-size: 0.8rem;
        color: rgba(209, 213, 219, 0.9);
        margin-top: 1px;
        white-space: pre-wrap;
        word-break: break-word;
      }
      .task-footer {
        display: flex;
        justify-content: space-between;
        align-items: center;
        margin-top: 5px;
      }
  
      .task-footer small {
        font-size: 0.72rem;
        color: var(--text-muted);
      }
  
      .task-actions {
        display: flex;
        gap: 4px;
      }
  
      .btn-icon {
        border: none;
        background: transparent;
        color: var(--text-muted);
        cursor: pointer;
        padding: 4px 5px;
        border-radius: 999px;
        font-size: 0.78rem;
        display: inline-flex;
        align-items: center;
        gap: 3px;
        transition: background 0.15s ease, color 0.15s ease, transform 0.06s ease;
      }
      .btn-icon span {
        font-size: 0.8rem;
      }
  
      .btn-icon:hover {
        background: rgba(31, 41, 55, 0.95);
        color: #f9fafb;
        transform: translateY(-0.5px);
      }
  
      .btn-icon--danger {
        color: rgba(248, 113, 113, 0.95);
      }
  
      .btn-icon--danger:hover {
        background: rgba(127, 29, 29, 0.9);
        color: #fee2e2;
      }
  
      .task.completed {
        opacity: 0.52;
        background: radial-gradient(circle at bottom, rgba(21, 128, 61, 0.22), rgba(15, 23, 42, 1) 65%);
        border-style: dashed;
      }
      .task.completed .task-title,
    .task.completed .task-notes {
      text-decoration: line-through;
      text-decoration-thickness: 1px;
      text-decoration-color: rgba(148, 163, 184, 0.9);
    }

    /* ====== Completed Section ====== */
    .completed-section {
      margin-top: 16px;
      padding-top: 11px;
      border-top: 1px solid rgba(31, 41, 55, 0.9);
    }

    .completed-header {
      display: flex;
      justify-content: space-between;
      align-items: baseline;
      margin-bottom: 8px;
    }

    .completed-header h2 {
      font-size: 0.85rem;
      text-transform: uppercase;
      letter-spacing: 0.16em;
      color: rgba(148, 163, 184, 0.95);
    }

    .completed-header small {
      font-size: 0.8rem;
      color: var(--text-muted);
    }
    .completed-list {
        display: flex;
        flex-wrap: wrap;
        gap: 8px;
      }
  
      .completed-pill {
        font-size: 0.75rem;
        border-radius: 999px;
        padding: 4px 9px;
        background: rgba(15, 23, 42, 0.96);
        border: 1px solid rgba(55, 65, 81, 0.96);
        color: rgba(209, 213, 219, 0.96);
        display: inline-flex;
        align-items: center;
        gap: 6px;
      }
  
      .completed-pill span {
        font-size: 0.8rem;
        color: rgba(22, 163, 74, 0.96);
      }
  
      .completed-empty {
        font-size: 0.8rem;
        color: rgba(148, 163, 184, 0.9);
      }