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

:root {
    --color-primary: #1b3a5c;
    --color-primary-dark: #0f2440;
    --color-primary-light: #2a5580;
    --color-accent: #d4a017;
    --color-accent-light: #f0c040;
    --color-bg: #eef1f5;
    --color-surface: #ffffff;
    --color-text: #2c3e50;
    --color-text-light: #6b7c8d;
    --color-border: #cdd5de;
    --color-border-light: #e2e8f0;
    --color-success: #27ae60;
    --color-danger: #e74c3c;
    --shadow-sm: 0 1px 3px rgba(0,0,0,0.08);
    --shadow-md: 0 4px 12px rgba(0,0,0,0.1);
    --shadow-lg: 0 8px 30px rgba(0,0,0,0.12);
    --radius: 8px;
    --radius-sm: 4px;
    --transition: 0.2s ease;
}

html {
    font-size: 15px;
    scroll-behavior: smooth;
}

body {
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto, Oxygen, Ubuntu, sans-serif;
    background: var(--color-bg);
    color: var(--color-text);
    min-height: 100vh;
    line-height: 1.6;
}

/* ===== Header ===== */
.app-header {
    background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 60%, var(--color-primary-light) 100%);
    color: #fff;
    padding: 0;
    box-shadow: 0 2px 12px rgba(15,36,64,0.3);
    position: sticky;
    top: 0;
    z-index: 100;
}

.header-inner {
    max-width: 1100px;
    margin: 0 auto;
    padding: 14px 24px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    flex-wrap: wrap;
}

.logo {
    display: flex;
    align-items: center;
    gap: 10px;
}

.logo-icon {
    font-size: 1.8rem;
    filter: drop-shadow(0 2px 4px rgba(0,0,0,0.3));
}

.logo-text {
    font-size: 1.5rem;
    font-weight: 700;
    letter-spacing: 1px;
    text-shadow: 0 1px 3px rgba(0,0,0,0.2);
}

.header-subtitle {
    font-size: 0.85rem;
    opacity: 0.8;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    font-weight: 300;
}

/* ===== Main Layout ===== */
.app-main {
    max-width: 1100px;
    margin: 0 auto;
    padding: 20px 24px 40px;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

/* ===== Palette Section ===== */
.palette-section {
    background: var(--color-surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border-light);
    padding: 16px 20px;
    transition: box-shadow var(--transition);
}

.palette-section:hover {
    box-shadow: var(--shadow-md);
}

.palette-title {
    font-size: 0.9rem;
    font-weight: 600;
    color: var(--color-primary);
    text-transform: uppercase;
    letter-spacing: 1px;
    margin-bottom: 12px;
    padding-bottom: 8px;
    border-bottom: 2px solid var(--color-accent);
    display: inline-block;
}

.palette-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 5px;
}

.palette-btn {
    width: 38px;
    height: 38px;
    border: 1px solid var(--color-border);
    border-radius: var(--radius-sm);
    background: #fafbfc;
    color: var(--color-text);
    font-size: 1.1rem;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition);
    line-height: 1;
    padding: 0;
    font-family: 'Cambria Math', 'Latin Modern Math', 'STIX Two Math', serif;
}

.palette-btn:hover {
    background: var(--color-primary);
    color: #fff;
    border-color: var(--color-primary);
    transform: scale(1.12);
    box-shadow: 0 2px 8px rgba(27,58,92,0.3);
    z-index: 1;
}

.palette-btn:active {
    transform: scale(0.95);
    background: var(--color-primary-dark);
}

/* ===== Editor Section ===== */
.editor-section {
    background: var(--color-surface);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
    border: 1px solid var(--color-border-light);
    overflow: hidden;
    transition: box-shadow var(--transition);
}

.editor-section:hover {
    box-shadow: var(--shadow-md);
}

/* Quill toolbar override */
.ql-toolbar.ql-snow {
    border: none !important;
    border-bottom: 2px solid var(--color-border) !important;
    background: linear-gradient(180deg, #f8f9fb 0%, #eef1f5 100%);
    padding: 10px 14px !important;
}

.ql-toolbar.ql-snow .ql-formats {
    margin-right: 8px;
}

.ql-toolbar.ql-snow .ql-picker-label,
.ql-toolbar.ql-snow button {
    border-radius: var(--radius-sm) !important;
}

.ql-toolbar.ql-snow button:hover,
.ql-toolbar.ql-snow .ql-picker-label:hover {
    border-color: var(--color-primary-light) !important;
    background: rgba(27,58,92,0.06) !important;
    color: var(--color-primary) !important;
}

.ql-toolbar.ql-snow button.ql-active,
.ql-toolbar.ql-snow .ql-picker-label.ql-active {
    color: var(--color-primary) !important;
    background: rgba(27,58,92,0.08) !important;
}

/* Custom formula buttons in toolbar */
#formula-btn,
#formula-inline-btn {
    width: auto !important;
    padding: 3px 8px !important;
    background: linear-gradient(135deg, var(--color-accent) 0%, #c49515 100%) !important;
    color: #fff !important;
    border: none !important;
    border-radius: var(--radius-sm) !important;
    font-size: 0.82rem !important;
    cursor: pointer !important;
    transition: all var(--transition) !important;
    box-shadow: 0 1px 3px rgba(212,160,23,0.3) !important;
}

#formula-btn:hover,
#formula-inline-btn:hover {
    background: linear-gradient(135deg, var(--color-accent-light) 0%, var(--color-accent) 100%) !important;
    transform: translateY(-1px) !important;
    box-shadow: 0 3px 8px rgba(212,160,23,0.4) !important;
}

#formula-btn:active,
#formula-inline-btn:active {
    transform: translateY(0) !important;
}

#undo-btn,
#redo-btn {
    font-size: 1rem !important;
    width: 30px !important;
}

/* Quill editor area */
.ql-container.ql-snow {
    border: none !important;
    font-size: 1rem;
    font-family: 'Segoe UI', -apple-system, BlinkMacSystemFont, Roboto, sans-serif;
    min-height: 400px;
}

#editor {
    min-height: 400px;
    padding: 20px 24px;
    font-size: 1rem;
    line-height: 1.75;
}

.ql-editor {
    min-height: 400px !important;
    padding: 20px 24px !important;
}

.ql-editor h1, .ql-editor h2, .ql-editor h3 {
    color: var(--color-primary);
    font-weight: 700;
    margin-top: 1em;
    margin-bottom: 0.4em;
}

.ql-editor h1 { font-size: 1.6rem; }
.ql-editor h2 { font-size: 1.35rem; }
.ql-editor h3 { font-size: 1.15rem; }

.ql-editor p {
    margin-bottom: 0.6em;
}

/* ===== Formula Blot Styles ===== */
.kb-formula-block {
    display: block;
    margin: 12px 0;
    padding: 16px 20px;
    background: #fafbfd;
    border-left: 4px solid var(--color-accent);
    border-radius: var(--radius-sm);
    text-align: center;
    overflow-x: auto;
    position: relative;
    cursor: pointer;
    transition: background var(--transition);
}

.kb-formula-block:hover {
    background: #f0f3f8;
}

.kb-formula-block .katex {
    font-size: 1.3em;
}

.kb-formula-inline {
    display: inline;
    cursor: pointer;
    border-radius: 2px;
    padding: 0 2px;
    transition: background var(--transition);
}

.kb-formula-inline:hover {
    background: rgba(212,160,23,0.1);
}

.kb-formula-inline .katex {
    font-size: 1.05em;
}

/* Edit overlay on hover */
.kb-formula-block::after,
.kb-formula-inline::after {
    content: '✎';
    position: absolute;
    top: 4px;
    right: 6px;
    font-size: 0.75rem;
    color: var(--color-text-light);
    opacity: 0;
    transition: opacity var(--transition);
}

.kb-formula-block::after {
    opacity: 0;
}

.kb-formula-block:hover::after {
    opacity: 0.6;
}

.kb-formula-inline {
    position: relative;
}

/* ===== Modal ===== */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(15,36,64,0.55);
    backdrop-filter: blur(4px);
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    animation: fadeIn 0.2s ease;
}

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

@keyframes slideUp {
    from { transform: translateY(30px); opacity: 0; }
    to { transform: translateY(0); opacity: 1; }
}

.modal-content {
    background: var(--color-surface);
    border-radius: 12px;
    box-shadow: var(--shadow-lg);
    width: 90%;
    max-width: 640px;
    max-height: 90vh;
    overflow-y: auto;
    animation: slideUp 0.25s ease;
}

.modal-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 18px 24px;
    border-bottom: 1px solid var(--color-border-light);
}

.modal-header h3 {
    color: var(--color-primary);
    font-size: 1.15rem;
    font-weight: 700;
}

.modal-close {
    background: none;
    border: none;
    font-size: 1.5rem;
    color: var(--color-text-light);
    cursor: pointer;
    width: 36px;
    height: 36px;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 50%;
    transition: all var(--transition);
}

.modal-close:hover {
    background: rgba(0,0,0,0.06);
    color: var(--color-text);
}

.modal-body {
    padding: 20px 24px;
}

.modal-body label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--color-primary);
    display: block;
    margin-bottom: 8px;
}

#latex-input {
    width: 100%;
    padding: 12px 14px;
    border: 2px solid var(--color-border);
    border-radius: var(--radius-sm);
    font-family: 'Consolas', 'Fira Code', monospace;
    font-size: 0.95rem;
    resize: vertical;
    transition: border-color var(--transition);
    outline: none;
    line-height: 1.5;
}

#latex-input:focus {
    border-color: var(--color-primary);
    box-shadow: 0 0 0 3px rgba(27,58,92,0.1);
}

.modal-hint {
    margin-top: 10px;
    padding: 10px 14px;
    background: #f0f4f8;
    border-radius: var(--radius-sm);
    font-size: 0.8rem;
    color: var(--color-text-light);
    line-height: 1.6;
}

.modal-hint code {
    background: #e2e8f0;
    padding: 1px 5px;
    border-radius: 3px;
    font-family: 'Consolas', 'Fira Code', monospace;
    font-size: 0.82rem;
    color: var(--color-primary-dark);
}

.preview-label {
    font-weight: 600;
    font-size: 0.9rem;
    color: var(--color-primary);
    margin-top: 16px;
    margin-bottom: 8px;
}

.formula-preview {
    min-height: 60px;
    padding: 16px 20px;
    background: #fafbfd;
    border: 2px dashed var(--color-border);
    border-radius: var(--radius-sm);
    display: flex;
    align-items: center;
    justify-content: center;
    overflow-x: auto;
}

.formula-preview .katex-error {
    color: var(--color-danger);
    font-size: 0.85rem;
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    padding: 16px 24px;
    border-top: 1px solid var(--color-border-light);
}

.btn {
    padding: 9px 22px;
    border: none;
    border-radius: var(--radius-sm);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition);
    letter-spacing: 0.3px;
}

.btn-primary {
    background: linear-gradient(135deg, var(--color-primary) 0%, var(--color-primary-light) 100%);
    color: #fff;
    box-shadow: 0 2px 6px rgba(27,58,92,0.3);
}

.btn-primary:hover {
    background: linear-gradient(135deg, var(--color-primary-dark) 0%, var(--color-primary) 100%);
    transform: translateY(-1px);
    box-shadow: 0 4px 10px rgba(27,58,92,0.4);
}

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

.btn-secondary {
    background: #eef1f5;
    color: var(--color-text);
    border: 1px solid var(--color-border);
}

.btn-secondary:hover {
    background: #e2e8f0;
}

/* ===== Quick Formula Templates ===== */
.quick-templates {
    margin-top: 14px;
    padding-top: 10px;
    border-top: 1px solid var(--color-border-light);
}

.quick-templates-title {
    font-size: 0.82rem;
    font-weight: 600;
    color: var(--color-text-light);
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 0.5px;
}

.quick-templates-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 6px;
}

.template-btn {
    padding: 4px 10px;
    font-size: 0.78rem;
    border: 1px solid var(--color-border);
    border-radius: 14px;
    background: #fafbfc;
    color: var(--color-text);
    cursor: pointer;
    transition: all var(--transition);
    white-space: nowrap;
}

.template-btn:hover {
    background: var(--color-primary);
    color: #fff;
    border-color: var(--color-primary);
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
    .header-inner {
        flex-direction: column;
        text-align: center;
        padding: 12px 16px;
    }

    .app-main {
        padding: 12px 12px 30px;
    }

    .palette-grid {
        gap: 4px;
    }

    .palette-btn {
        width: 34px;
        height: 34px;
        font-size: 0.95rem;
    }

    #editor {
        min-height: 300px;
    }

    .ql-editor {
        min-height: 300px !important;
    }

    .modal-content {
        width: 96%;
    }

    .modal-body {
        padding: 14px 16px;
    }

    .quick-templates-grid {
        gap: 4px;
    }
}

/* ===== Print Styles ===== */
@media print {
    .app-header,
    .palette-section,
    #toolbar,
    .modal-overlay {
        display: none !important;
    }

    .editor-section {
        box-shadow: none;
        border: none;
    }

    .ql-toolbar {
        display: none !important;
    }
}

/* ===== Scrollbar ===== */
::-webkit-scrollbar {
    width: 8px;
    height: 8px;
}

::-webkit-scrollbar-track {
    background: #eef1f5;
}

::-webkit-scrollbar-thumb {
    background: #b0bec5;
    border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
    background: #90a4ae;
}

/* ===== Selection ===== */
::selection {
    background: rgba(27,58,92,0.15);
}